Diagnosing Disease: The Process of Detecting and Identifying Illness

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Chapter 3
Diagnosing Disease: The Process of Detecting and Identifying Illness

Diagnosis means finding the cause of a disorder, not just giving it a name.

—Sydney Walker III

The practice of medicine often is considered to be both science and art because identifying the underlying causes of disease and establishing a diagnosis require that health care practitioners use a combination of scientific method, intuition, and interpersonal (communication and human relations) skills. Diagnosis relies on the powers of observation; listening and communication skills; analytical ability; knowledge of human anatomy (structure and parts of the human body) and physiology (the functions and life processes of body systems); and an understanding of the natural course of illness.

The editors of the sixteenth edition of Harrison's Principles of Internal Medicine (Eugene Braunwald et al., eds., New York: McGraw-Hill Professional, 2004) explain that diagnosis requires a logical approach to problem solving involving analysis and synthesis. In other words, health care practitioners must systematically break down the information they obtain from a patient's medical history, physical examination, and laboratory test results and then reassemble it into a pattern that fits a well-defined syndrome (a group of symptoms that collectively describe a disease).


Obtaining a complete and accurate medical history is the first step in the diagnostic process. In fact, many health care practitioners (physicians, nurses, and allied health professionals) believe that the patient's medical history is the key to diagnosis and that the physical examination and results of any diagnostic testing (laboratory analyses of blood or urine, x-rays, or other imaging studies) simply serve to confirm the diagnosis made on the basis of the medical history.

A medical history is developed using data collected during the health care practitioner's interview with the patient. The medical history also may include data from a health history form or health questionnaire completed by the patient before the visit with the practitioner. The objectives of taking a medical history are as follows:

  • Obtain, develop, and document (in writing) a clear, accurate, chronological account of the individual's medical history (including a family history, employment history, social history, and other relevant information) and current medical problems.
  • List, describe, and assign priority to each symptom, complaint, and problem presented.
  • Observe the patient's emotional state as reflected in voice, posture, and demeanor.
  • Establish and enhance communication, trust, understanding, and comfort in the physician-patient (or nurse-patient) relationship.

In addition to eliciting a history of all of the patient's previous medical problems and illnesses, the health care practitioner asks questions to learn about the history of the present illness or complaint—how and when it began, the nature of symptoms, aggravating and relieving factors, its effect on function, and any self-care measures the patient has taken.

The medical history also includes a review of physiological systems—such as the cardiovascular (related to heart and circulation), gastrointestinal (GI; digestive disorders), psychiatric (mental and emotional health), and neurologic (brain and nerve disorders) systems—through which the patient may experience symptoms of disease. The review of systems frequently helps the practitioner obtain information to help assess the severity of the present problem and confirm the diagnosis.

Because it relies on the patient's assessment of the severity, duration, and other characteristics of symptoms, as well as the patient's memories and interpretation of past illnesses, the medical history provides the practitioner with subjective information. Together with the objective findings of the physical examination and other diagnostic tests, it helps practitioners to identify disease correctly.


The National Institutes of Health's U.S. National Library of Medicine (http://www.nlm.nih.gov/index.html) defines physical examination as "the process of examining the patient's body to determine the presence or absence of physical problems." It includes inspection (looking), palpation (feeling), auscultation (listening), and percussion (tapping to produce sounds).

Vital Signs

In a clinic or office-based medical practice, the physical examination may begin with a nurse or medical assistant measuring the patient's vital signs—temperature, respiration, pulse, and blood pressure. Temperature is measured using a thermometer. Normal oral temperature (measured by mouth) is 98.6 degrees Fahrenheit or 37 degrees Celsius. Temperature also may be measured rectally, under the arm (axillary), or aurally with an electronic thermometer placed in the ear.

Respiration is measured by observing the patient's rate of breathing. In addition to determining the rate of respiration (normal for an adult is twelve to twenty breaths per minute), the practitioner also notes any difficulties in breathing.

Pulse rate and rhythm are assessed by compressing the resting patient's radial artery at the wrist. The normal resting pulse rate is between sixty and one hundred beats per minute, and the rhythm should be regular, with even spaces between beats. Pulse rates higher than one hundred beats per minute are called tachycardia, and rates lower than sixty beats per minute are called bradycardia. Some variations in pulse rates are considered normal and do not signify disease. Athletes who engage in high levels of physical conditioning often have pulse rates of less than sixty beats per minute at rest. Similarly, pulse rates increase naturally in response to exercise or emotional stress.

Blood pressure is measured using an inflatable blood pressure cuff, also known as a sphygmomanometer. Blood pressure is measured in millimeters of mercury (mm Hg). Two readings are recorded—systolic pressure is the top number of a blood pressure reading and represents the pressure at which beats are first heard in the artery. The bottom number is the pressure at which the beats can no longer be heard; it is called diastolic pressure. As with pulse rates, blood pressure varies in response to exercise and emotional stress. Normally, the systolic blood pressure of an adult is less than 140 mm Hg and diastolic blood pressure is less than 90 mm Hg. Repeated blood pressure readings higher than 140/90 mm Hg lead to a diagnosis of hypertension (high blood pressure).

Head and Neck

Physical examination of the head and neck involves inspection of the head (including skin and hair), ears, nose, throat, and neck. An instrument called an otoscope is used to examine the ear canal and tympanic membrane for swelling, redness, lesions, drainage, discharge, or deformity. Inspecting the throat, the practitioner looks for abnormalities and, by depressing the tongue, can inspect the mouth, oropharynx, and tonsils.

The practitioner notes any scars, asymmetry, or masses (lumps or thickenings) in the neck and systematically palpates (presses) to examine the chains of lymph nodes (also known as "lymph glands," clusters of cells that filter fluid known as lymph) that run in front and behind the ear, near the jaw, and at the base of the neck. The practitioner also inspects and palpates the thyroid gland (the largest gland in the endocrine system, located where the larynx and trachea meet).

Eye Examination

An eye examination consists of a vision test and visual inspection of the eye and surrounding areas for abnormalities, deformities, and signs of infection. Two numbers describe visual acuity (vision). The first number is the distance (in feet) that the patient is standing from the test chart, and the second number is the distance from which the eye can read a line of letters from the test chart. Because 20/20 is considered normal vision, a person with 20/60 vision can read a line of letters from twenty feet away that a person with normal vision could read from a distance sixty feet away from the test chart. Using an ophthalmoscope, the practitioner examines the inner structures of the eye by looking through the pupil.

Chest and Lungs

Examination of the chest and lungs focuses on identifying disorders of breathing, which consists of inspiration and expiration (inhaling and exhaling). Changes in the length of either action could be a sign of disease. For example, prolonged expiration may be the result of the airway obstruction of asthma.

Percussion is a tapping technique used to produce sounds on the chest wall that may be distinguished as normal, dull, or hyperresonant. Dull sounds may indicate the presence of pneumonia (infection of the lungs), whereas hyperresonant sounds may be signs of a collapsed lung (pneumothorax) or emphysema (a disease in which the alveoli—microscopic air sacs—of the lung are destroyed).

The practitioner listens to breath sounds with a stethoscope. Listening with the stethoscope is called auscultation. Decreased breath sounds may be signs of emphysema or pneumothorax (a collection of air or gas in the chest that causes part or all of a lung to collapse), whereas high-pitched wheezes are associated with asthma. Another device used to monitor the breathing of patients with asthma is a peak flow meter. After taking a deep breath, the patient exhales into the peak flow meter and it measures the velocity of exhaled breath.

Back and Extremities

The examination of the back and extremities (arms and legs) focuses on the anatomy of the musculoskeletal system. Major muscle groups and all joints are examined, and pulses on the arms, legs, and feet (radial, posterior tibial, and dorsalis pedis respectively) are checked to be certain blood flow to the extremities is adequate. Monitoring capillary refill time is another way to assess the adequacy of blood flow. To do this, the practitioner presses the patient's fingernail or toenail until it pales and then observes how long it takes to regain color once the pressure is released. Longer capillary refill time may be a sign of peripheral vascular disease or blocked arteries.

Cardiovascular System

The examination of the cardiovascular system focuses on the rate and rhythm of radial and carotid artery pulses (located at the wrist and neck), blood pressure, and the sounds associated with blood flow through the carotid arteries and the heart. After measuring and recording the rate and rhythm of radial and carotid pulses, the practitioner may listen with a stethoscope for abnormal sounds in the carotid arteries. Rushing sounds, called "bruits," may indicate narrowing of the arteries and an increased risk for stroke.

Examination also entails assessment of jugular vein pressure and listening with a stethoscope to heart sounds. Heart murmurs, clicks, and extra sounds are abnormal heart sounds associated with the functioning of heart valves. Some murmurs are considered "innocent" (normal variations), whereas others are indicators of serious malfunctioning of heart valves.

Abdominal Examination

Inspection of the abdomen focuses on the shape and movement of the abdomen and the presence of scars, lesions, rashes, and hernias (protrusion of an organ through a wall that usually encloses it). Using a stethoscope, the practitioner listens to the arteries that supply blood to the kidneys, listens to the aorta (the main artery that supplies blood to all the organs except the lungs), and listens for bowel sounds.

Percussion of the abdomen that produces a dull sound may indicate an abnormality, such as an abdominal mass. Percussion also is used to determine the size of the liver (the largest gland in the body, which produces bile to aid in the digestion of fats) that measures six to twelve centimeters in a healthy adult. An expanse of dullness around the liver or spleen (an organ on the left side of the body, below the diaphragm, that filters and stores blood) may indicate that these organs are enlarged.

Breast and Pelvic Examination

Visual inspection of the breast focuses on symmetry, dimpling, swelling or discoloration of skin, and position of the nipple. Manual breast examination is performed by slowly and methodically palpating breast tissue in overlapping vertical strips using small circular movements from the midline to the axilla (armpit). The practitioner presses the nipple to observe whether there is any discharge (fluid) and also palpates the axilla for the presence of lymph nodes.

Pelvic examination often is performed after the breast examination, during a woman's physical examination. At this time, a sample of tissue usually is obtained for a Papanicolaou (Pap) smear, which is examined microscopically for cervical cancer cells in the cytology laboratory.

Neurologic and Mental Status Examinations

Neurologic examination considers mental status, cranial nerves (the twelve cranial nerves are olfactory, optic, oculomotor, trochlear, trigeminal, abducens, facial, acoustic, glossopharyngeal, vagus, accessory, and hypoglossal), muscle strength, coordination and gait, reflexes, and the senses.

Generally, the cranial nerves are assessed by observation as the health care practitioner asks the patient to demonstrate their use. For example, the facial nerve may be tested by watching patients open their mouths and clench their teeth. The practitioner also tests sensation to the parts of the face supplied by branches of the trigeminal nerve by applying sharp and dull objects to these areas and asking the patient to distinguish between them. Finally, the practitioner touches the patient's cornea lightly to observe whether the patient blinks—the corneal reflex is present.

Evaluating the motor system involves assessment of muscle symmetry, tone, strength, gait, and coordination. Patients are observed performing different skills and walking. Reflexes are tested and graded as "normal," "hypoactive," or "hyperactive." An example of reflex testing is when the practitioner strikes the patellar tendon just below the kneecap to observe contraction of the quadriceps muscle in the thigh and extension of the knee.

The sensory system test determines whether there is loss of sensation in any body part. The practitioner may use the vibrations from a tuning fork or hot, cold, or sharp objects to evaluate patients' abilities to perceive sensation accurately. The practitioner also may test discrimination—the ability to accurately interpret touch and position—by tracing a number on the patient's palm and asking the patient to name the number.

A preliminary evaluation of mental status aims to determine the patient's orientation, immediate and short-term memory, and ability to follow simple verbal and written commands. Patients are considered "oriented" if they can identify time, place, and person accurately. Immediate and short-term memories are tested when the practitioner poses simple questions for the patient to answer, and the ability to follow commands is assessed by observing patients perform tasks in response to verbal or written instructions.

Americans Want Annual Physicals

In recent years the American Medical Association and other medical professional societies have downplayed the importance of traditional "head-to-toe" annual physical examinations. Instead, they favor a "periodic health examination"—an individualized screening and examination based on the patient's age, health status, lifestyle, and risk factors.

A November 2005 Gallup Poll found that Americans remain fans of annual physical exams—95% feel it is important for people their age to have routine medical examinations each year, and more than three-quarters (78%) said they had a routine examination in the past year. (See Figure 3.1.) Gallup reported that more women (83%) than men (73%) reported having a medical checkup in the past year, and more nonsmokers (80%) than smokers (74%) obtained medical checkups (Lydia Saad, What's the Prognosis for Annual Medical Checkups? The Gallup Organization, November 29, 2005).


Once the history and physical examination have been completed, the health care practitioner is often relatively certain about the cause of illness and the diagnosis. However, occasions occur when the history and physical examination point to more than one possible diagnosis. In such instances, the practitioner develops a "differential diagnosis"—a list of several likely diagnoses. The practitioner then may order specific diagnostic tests to narrow the list of possibilities. The results of these tests are evaluated in the context of the patient's history and physical examination.

There are scores of diagnostic tests—blood tests, x-rays, computed tomography (CT) scans, ultrasounds, magnetic resonance imaging (MRI)—to help the health care practitioner identify the cause of disease. It is important for practitioners to choose tests that not only improve their understanding of the disease but also affect treatment decisions. The decision to order a specific diagnostic test takes into account the test's reliability, validity, sensitivity, and specificity in addition to its risks to the patient and costs in terms of time and dollars.

The Reliability and Validity of Diagnostic Tests

Reliability of diagnostic testing refers to the test's ability to be repeated and to produce equivalent results in comparable circumstances. A reliable test is consistent and measures the same way each time it is used with the same patients in the same circumstances. For example, a well-calibrated balance scale is a reliable instrument for measuring body weight.

Validity is the accuracy of the diagnostic test. It is the degree to which the diagnostic test measures the disease, blood level, or other quality or characteristic it is intended to detect. A valid diagnostic test is one that can distinguish between those who have the disease from those who do not. There are two components of validity—sensitivity and specificity.


Sensitivity refers to a test's ability to identify people who have the disease. Specificity, on the other hand, refers to a test's ability to identify people who do not have the disease. Ideally, diagnostic tests would be highly sensitive and highly specific, thereby accurately classifying all people tested as either positive or negative. In practice, however, sensitivity and specificity are frequently inversely related—most tests with high levels of sensitivity have low specificity, and the reverse is also true.

The likelihood that a test result will be incorrect can be gauged based on the sensitivity and specificity of the test. For example, if a test's sensitivity is 95%, then when one hundred patients with the disease are tested, ninety-five will test positive and five will test "false negative"—they have the disease but the test has failed to detect it.

However, if a test is 90% specific, when one hundred healthy, disease-free people are tested, ninety will receive negative test results and ten will be given "false-positive" results—they do not have the disease but the test has inaccurately classified them as positive.

The advantages of highly sensitive tests are that they produce few false-negative results, and people who test negative are almost certain to be truly negative. Highly sensitive tests may be useful as preliminary screening measures for diseases where early detection is vitally important, such as the enzyme-linked immunosorbent assay (ELISA) screening test for human immunodeficiency virus (HIV), the virus that produces acquired immune deficiency syndrome (AIDS).

In contrast, highly specific tests produce very few false-positive results and those who test positive are nearly certain to be positive. Highly specific tests are useful when confirming a diagnosis and in cases where the risks of treatment are high, such as the Western blot test to confirm the presence of HIV after it has been detected by the highly sensitive, but less specific, ELISA test.

Laboratory Tests

The editors of Harrison's Principles of Internal Medicine observe that the growing number and availability of laboratory tests has encouraged physicians and other health care practitioners to become increasingly reliant on them as diagnostic tools. Laboratory tests are easy, convenient screening measures because multiple tests may be performed on a single sample of blood and abnormal test results can provide valuable clues for diagnosis.

For screening purposes (to detect disease at its earliest stage, before it produces symptoms), the health care practitioner may order a variety of blood tests, including:

  • Fasting blood sugar—This test is a screening and diagnostic test for diabetes; values consistently greater than 126 mg/dl indicate diabetes.
  • Calcium—Blood levels of calcium can be elevated as a result of hyperactive parathyroid glands.
  • Lipids—Elevated cholesterol, triglycerides, and low-density lipoproteins are associated with increased risk of heart disease.
  • Thyroid stimulating hormone (TSH)—High levels of TSH indicate hypothyroidism (underactivity of the thyroid gland), and abnormally low levels indicate hyperthyroidism (overly active thyroid gland).
  • VDRL (Venereal Disease Research Laboratory) or RPR (rapid plasma reagin)—These tests screen for syphilis, a sexually transmitted disease.
  • HIV—It is important to screen for the presence of the virus that causes AIDS.
  • PSA (prostate specific antigen)—This blood test is used to screen for prostate cancer and to monitor treatment of the disease.
  • Stool occult blood (also called fecal occult blood test)—This tests for the presence of blood in the stool, which could be an indicator of colon cancer.

Diagnostic Imaging Techniques

Imaging studies are another form of diagnostic testing. In the past all diagnostic imaging studies were obtained using ionizing radiation (x-rays) and recorded on transparent film. Modern imaging studies such as ultrasound and magnetic resonance imaging (MRI) use nonionizing radiation and can be recorded digitally, viewed on computer monitors, sent via electronic mail, and stored on compact discs, digital tape, or transparent film. Most imaging studies are painless and pose little risk to patients apart from minimal exposure to radiation.


The images produced by x-rays are the result of varying radiation absorption rates of different body tissues—the calcium in bone has the highest x-ray absorption, soft tissue such as fat absorbs less, and air absorbs the least. Chest x-rays, which offer images of the lungs, ribs, heart, and diaphragm, are among the most frequently ordered imaging studies.

To view tissues normally invisible on x-ray, contrast agents, such as barium and iodine, may be introduced into the body. For example, contrast agents often are used for imaging studies of the GI tract to diagnose digestive disorders.

Another common use of diagnostic x-rays is the measurement of bone density. Bone mass measurement (also called bone mineral density) is performed to evaluate the risk of bone fractures. Bone density usually is measured in the spine, hip, and/or wrist because these are the most common sites of fractures resulting from osteoporosis, a disease in which bones become weak, thin, fragile, and more likely to break.

Mammography also relies on x-ray technology to detect and pinpoint changes or abnormalities in the breast tissue that are too small to be felt by hand. Another imaging technique for breast examination is ultrasound, which can accurately distinguish solid tumors (lumps or masses) from fluid-filled cysts.

Ultrasound images are produced using the heat reflected from body tissues in response to high-frequency sound waves. Whereas x-ray is ideal for examining bone, ultrasound is used to examine soft tissue, such as the ovaries, uterus, breast, and prostate. It is not suitable for looking at bones, because calcium-containing tissues such as bone absorb, rather than reflect, sound waves.


For conventional flat x-rays, the patient, x-ray source, and camera remain fixed and immobile. Computed tomography (CT) scans use a mobile x-ray source and generate a series of cross-section pictures, or slices, that are assembled by computer into images. Because CT distinguishes differences in soft tissue more effectively and with higher resolution than conventional x-rays, it often is used to examine internal organs in the abdomen, such as the liver, pancreas, spleen, kidneys, and adrenal gland, and the aorta and vena cava (large blood vessels that pass through the abdomen).

Magnetic resonance imaging (MRI) generates images based on interaction between a large magnet, radio waves, and hydrogen atoms in the body. Stimulated by ordinary radio waves within the powerful magnetic field, these atoms give off weak signals that a computer builds into images. MRI frequently is used to create images of the brain, spinal cord, heart, abdomen, bone marrow, and knee.

CT and MRI scans generate images of the body's structure (anatomy), whereas positron emission tomography (PET) scans offer insight into body function or processes (physiology). To create PET images, positron-emitting atoms are injected into the body, where they travel and strike other electrons, producing gamma rays. The gamma rays then are interpreted into images by a computer. Unlike CT and MRI, PET rarely is used for screening or diagnostic purposes. Instead, it is used to track the progress and treatment of patients with diagnosed diseases such as cancer.

Diagnostic Procedures

Other diagnostic tests commonly performed to screen for the presence of disease include the following:

  • Throat culture—This test is used to determine whether streptococcus pyrogenes (commonly called strep) bacteria are the cause of a sore throat. To obtain a sample of the mucus in the throat, the health care practitioner swabs the back of the throat and places the swab in a tube. The swab is transferred into a culture in the laboratory where it is examined for bacterial growth. The results of this test are available in two to three days. A "rapid" strep test that produces results in minutes is also available.
  • Urinalysis and urine culture—Chemical and microscopic examination of urine allow identification of infection, diabetes, and the presence of blood in the urine.
  • Colonoscopy—Using a long tube fitted with a lens, the health care practitioner is able to look at the entire colon; identify and remove polyps; detect cancer; and diagnose other causes of blood in the stool, abdominal pain, and digestive disorders. To prepare for a colonoscopy, patients must empty their intestines completely before the examination.
  • Flexible sigmoidoscopy—This test is similar to the colonoscopy in its use of a tube fitted with a camera to examine the colon. However, because the instrument is shorter than a colonoscope, it does not enable views of the entire colon. Through the flexible sigmoidoscope, the practitioner can examine only the sigmoid (lower portion) of the colon to detect polyps and cancers.
  • Electrocardiogram—This test assesses the electrical function of the heart, detects abnormal heart rhythms, and aids in the diagnosis of myocardial infarction (heart attack) and other heart diseases.

Prenatal Diagnostic Testing

Ultrasound is used routinely to monitor the progress of pregnancy; evaluate the size, health, and position of the fetus; and detect some birth defects. Fetal ultrasound assists in the prediction of multiple births (more than one baby) and sometimes provides information about the gender of the unborn child.

Chorionic villus sampling (CVS) enables obstetricians and perinatologists (physicians specializing in evaluation and care of high-risk expectant mothers and babies) to assess the progress of pregnancy during the first trimester (the first three months). A physician passes a small, flexible tube called a catheter through the cervix to extract chorionic villi tissue—cells that will become the placenta and are genetically identical to the baby's cells. The cells are examined in the laboratory for indications of genetic disorders such as cystic fibrosis, Down syndrome, Tay-Sachs disease, and thalassemia. The results of the testing are available within seven to fourteen days. CVS provides the same diagnostic information as amniocentesis; however, the risks (miscarriage, infection, vaginal bleeding, birth defects) associated with CVS are slightly higher.

Amniocentesis involves analyzing a sample of fluid that surrounds the fetus in the uterus. The fluid is obtained when a physician inserts a hollow needle through the abdominal wall and the uterine wall. Like CVS, amniocentesis samples and analyzes cells derived

from the baby to enable parents to learn of chromosomal abnormalities and the gender of the unborn child. Results usually are available about two weeks after the test is performed.

Blood tests are also available to help diagnose fetal abnormalities. The enhanced alpha-fetoprotein test (also called a triple screen) measures levels of protein and hormones produced by the fetus and can identify some birth defects, such as Down syndrome and neural tube defects. Two of the most common neural tube defects are anencephaly (absence of the majority of the brain) and spina bifida (incomplete development of the back and spine). Test results are available within two to three days. Women with abnormal results often are advised to undergo additional diagnostic testing, such as CVS or amniocentesis.


Unlike physical health problems and medical conditions, there are no laboratory tests such as blood and urine analyses or x-rays to assist practitioners to definitively diagnose mental illnesses. Instead, practitioners generally rely on listening carefully to patients' complaints and observing their behavior to assess their moods, motivations, and thinking. Sometimes mental health disorders may accompany physical complaints or medical conditions. The presence of more than one disease or disorder is termed comorbidity.

Although there are varying opinions about the personality traits and characteristics that taken together constitute optimal mental health, historically it has been somewhat easier to define and identify mental illness—deviations from, or the absence of, mental health. Within the broad diagnosis of mental illness, there is more consensus about the origins, nature, and symptoms of mental disorders—serious, and often long-term conditions in which changes in cognition (thinking), behavior, or mood impair functioning—than exists about mental health problems—shorter term, less intense conditions that often resolve spontaneously, without treatment.

Because many mental health disorders are identified by primary-care physicians (general practitioners, family practitioners, internists, and pediatricians), the World Health Organization (WHO) developed educational materials and guidelines to assist practitioners in general medical settings—as opposed to psychiatric or other mental health settings—to assess and treat the mental health problems and disorders of patients in their care. The guidelines describe an assessment interview as a series of screening questions for which predominantly positive answers suggest the patient has an "identified mental disorder," or a "subthreshold disorder"—the patient responds positively to many questions but not enough to fulfill the diagnostic criteria for a disorder as defined by the WHO's tenth revision of the International Classification of Diseases (ICD-10), the European guide for diagnosis of mental disorders. In North America the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV; Washington, DC: American Psychiatric Association, 2000) is used for the same purpose as the ICD-10. Practitioners are encouraged to ask open-ended questions that encourage patients to freely express their emotions, assure confidentiality, to acknowledge patients' responses, and to closely observe their body language and tones of voice.

Changing Criteria for Mental Illness

There are many controversies in mental health diagnosis, beginning with the definitions and classification of mental illnesses. Which criteria distinguish conditions as mental illness rather than normal variations in thinking and behavior? Should conditions such as attention deficit hyperactivity disorder (ADHD) be classified as learning problems or mental disorders? Should practitioners distinguish between neurological conditions that cause brain dysfunction and cognitive impairment such as Alzheimer's disease and mental illness involving brain dysfunction such as depression that may result from an imbalance of chemicals in the brain?

DSM-IV, as mentioned above, is the authoritative encyclopedia of diagnostic criteria for mental disorders. This definitive guide, which expands upon the ICD-10, is the most widely used psychiatric reference in the world and catalogs more than three hundred mental disorders. Table 3.1 lists the major classifications of mental disorders contained in the DSM-IV.

An examination of past versions of the DSM reveals that the definitions of mental illnesses have changed


Major diagnostic classes of mental disorders (DSM-IV)

Disorders usually first diagnosed in infancy, childhood, or adolescence

Delerium, dementia, and amnestic and other cognitive disorders

Mental disorders due to a general medical condition

Substance-related disorders

Schizophrenia and other psychotic disorders

Mood disorders

Anxiety disorders

Somatoform disorders

Factitious disorders

Dissociative disorders

Sexual and gender identity disorders

Eating disorders

Sleep disorders

Impulse-control disorders

Adjustment disorders

Personality disorders

source: "Table 2-5. Major Diagnostic Classes of Mental Disorders (DSM-IV)," in Mental Health: A Report of the Surgeon General, U.S. Department of Health and Human Services, Substance Abuse and Mental Health Services Administration, with NIH, 1999, http://www.surgeongeneral.gov/library/mentalhealth/chapter2/sec2.html (accessed January 18, 2006)

dramatically from one edition to another. Persons diagnosed with a specific mental disorder based on diagnostic criteria in one edition might no longer be considered mentally ill according to the next edition. Critics of the DSM, which has expanded more than tenfold since its inception, claim that diseases are added arbitrarily by the American Psychiatric Association (APA) and that while some entries represent changing ideas about mental health and illness, others are politically motivated. For example, homosexuality was once considered a mental illness, but today, largely in response to changing societal attitudes, it is no longer termed an illness.

Skeptics also question the sharp increase in the number of diagnoses and the number of Americans receiving these diagnoses. Does the increasing number of diagnoses reflect rapid advances in mental health diagnostic techniques? Have mental health professionals simply improved their diagnostic skills? Are the stresses of twenty-first-century life precipitating an epidemic of mental illness in the United States? Or are mental health professionals—psychiatrists, psychologists, clinical social workers, marriage and family therapists, and other mental health practitioners—simply labeling more behaviors and aspects of everyday life as pathological (diseased)?

Further, there is dissent even within the mental health field about diagnosis that is rooted in the ongoing debate about the origins of mental illness. After taking into account all of the relevant medical research, Mental Health: A Report of the Surgeon General (1999, http://www.surgeongeneral.gov/library/mentalhealth/home.html) concluded that for most mental illnesses there is no demonstrable physiological cause. This means there is no laboratory test, imaging study (x-ray, magnetic resonance imaging, or positron emission tomography), or abnormality in brain tissue that has been definitively identified as causing mental illness. The majority of persons suffering from mental illness apparently have normal brains, and those with abnormal brain structure or function are diagnosed with neurological disorders rather than mental illnesses.

Finally, there are those who view mental illness as a social condition rather than one requiring medical diagnosis. They observe that even the Surgeon General's report, which favors biological explanations of the origin, diagnosis, and treatment of mental illness, concedes that mental health is poorly understood and defined differently across cultures. If mental health and illness are rooted in cultural mores and values, then they are likely socioeconomic and political in origin. The proponents of societal causes of mental illness contend that if mental illness is in part defined as functional impairment, and during the course of their lives perhaps half the U.S. population will be impaired (according to the National Institute of Mental Health [NIMH], 2006, http://www.nimh.nih.gov/publicat/numbers.cfm), then perhaps it is not the individual who is ailing, but the society. This theory is supported by the fact that the WHO, in their World Health Report (2001, http://www.who.int/whr/2001/en/), estimates that 25% of individuals will be diagnosed with mental illness in developed and developing countries, half of the proportion of the American population estimated to be at risk.

Despite the challenges of diagnosing metal illnesses, there is consensus that early diagnosis is vital because untreated psychiatric disorders can produce more frequent and more severe episodes, are more likely to become resistant to treatment, and may lead to the development of co-occurring mental illnesses. NIMH cites research revealing that while about 80% of all people in the United States with a mental disorder eventually do seek treatment, there are personal and public health consequences that result from long delays in seeking and receiving treatment. Untreated mental disorders are associated with school failure, teenage childbearing, unstable employment, marital instability, and violence ("Mental Illness Exacts Heavy Toll, Beginning in Youth," NIMH, June 6, 2005, http://www.nimh.nih.gov/press/mentalhealthstats.cfm).

Projective Testing Techniques

Most diagnoses of mental illness are made on the basis of symptoms reported by the patient, the practitioner's observations, and the use of designated guidelines or criteria for distinguishing between disorders and establishing diagnoses. There are, however, additional diagnostic tests practitioners may perform to confirm diagnoses. Projective tests are thought to provide insight into clients' unconscious minds and have been used to characterize and describe symptoms, as well as to detect physical abuse, sexual abuse, and child abuse. They include the Rorschach test, Thematic Apperception Test (TAT), human figure drawings, and the Washington University Sentence Completion Test. There is widespread agreement that projective tests should be just one component of a comprehensive diagnostic study and that results from the tests should be integrated with history and interview information, because test results should be weighted only when they are consistent with other data.

There has been harsh criticism of projective tests during recent years, with detractors detailing their shortcomings, concluding that they lack a scientific underpinning and produce exaggerated estimates of pathology. In an effort to address this controversy, Howard Garb and his colleagues analyzed the efficacy of a variety of projective tests and reported their findings in "Effective Use of Projective Techniques in Clinical Practice: Let the Data Help with Selection and Interpretation" (Professional Psychology: Research and Practice, vol. 33, no. 5, October 2002).

The investigators concluded that for making diagnoses, psychologists should rely primarily on interview and history information, but that results from psychological tests, including self-report personality inventories and projective techniques, may be helpful. They advised psychologists that they were likely to be "on safer ground when they use projective techniques as an aid for exploration in psychotherapy rather than as an assessment device."

Further, the investigators exhorted psychologists to rely heavily on history and interview data to predict behavior. They recommended that to evaluate psychiatric symptoms and personality traits, practitioners should depend on interview and history information, self-report personality inventories, and, in selected instances, projective tests. Although evaluation of symptoms and personality traits are ostensibly the ideal task for projective techniques, the investigators found that findings derived from Rorschach, TAT, and human figure drawings have not been independently and consistently replicated.

Automated and Online Diagnostic Testing

There are other diagnostic tests and case-finding instruments—tools practitioners may employ to screen for and identify persons suffering from mental illness. Jonathan Shedler and his colleagues from Harvard Medical School and the Clinical Research Unit of Kaiser Permanente in Colorado evaluated the utility and validity of Quick PsychoDiagnostics (QPD) Panel, an automated mental health test. They reported their findings in "Practical Mental Health Assessment in Primary Care: Validity and Utility of the Quick PsychoDiagnostics Panel" (Journal of Family Practice, vol. 49, no. 7, July 2000).

QPD was designed to meet the needs of primary-care physicians who do not have sufficient time to administer even brief diagnostic tests. The test combines features of an inventory and a structured interview and screens for nine frequently occurring psychiatric disorders and requires no physician time to administer or score. Patients respond to a core set of fifty-nine questions and, when responses suggest a possible psychiatric disorder, the test offers pointed questions that, like a structured interview, probe in depth. Although the test contains more than two hundred diagnostic questions, patients see and respond to a customized, relevant subset of them. Scoring is performed electronically.

The investigators evaluated validity by correlating QPD Panel scores to the Structured Clinical Interview for DSM-IV (SCID) and established mental health measures. They assessed utility, in terms of acceptability to physicians and patients, by administering satisfaction surveys to both groups. The researchers concluded that the QPD Panel is a valid mental health assessment tool with the capacity to diagnose a range of common psychiatric disorders. They deemed it practical for routine use in busy primary-care practices and observed that "routine screening would benefit the many patients who currently go undiagnosed and untreated."

Even if computerized diagnostic capabilities are imperfect and unproved, University of Pittsburgh Department of Psychiatry researcher Howard Garb suggested that computer programs will become more prominent in mental health practice in "Computers Will Become Increasingly Important for Psychological Assessment: Not That There's Anything Wrong with That!" (Psychological Assessment, vol. 12, no. 1, March 2000). Garb contended that computers would be widely used for psychological assessment because mental health professionals are not good at some judgment tasks and that the use of computers to make judgments might prevent problems associated with clinicians' judgments. He concluded, "Using computers to make judgments and decisions in personality assessment can lead to dramatically improved reliability, a decrease in the occurrence of biases, and an overall increase in validity and utility."

Tom Buchanan from the University of Westminster Department of Psychology described the strengths and weaknesses of Internet-mediated, or online, psychological assessment in "Online Assessment: Desirable or Dangerous?" (Professional Psychology: Research and Practice, vol. 33, no. 2, April 2002). Buchanan cited the strengths of online personality testing as allowing more people to complete them than would otherwise be possible. It enables persons who were previously unable to do so, because of distance or time constraints, to access mental health services. (Those who favor online therapy or counseling make the same arguments.) There also is the possibility that people may be more candid when completing tests online and willing to disclose more information about themselves to computers than to other people.

Weaknesses of Web-based assessment include computer anxiety that may affect participants' responses and the observation that online respondents tend to report higher levels of negative affect than those who complete conventional paper questionnaires. Mental health researchers wonder whether online respondents are simply more inclined to self-disclosure or whether they are actually a more depressed group. There are also professional and ethical concerns such as the likelihood of well-meaning but untrained individuals who offer tests and opinions about a range of psychological conditions. One concern is the consequences of providing already troubled individuals with information that might be potentially distressing. Without appropriate follow-up or counseling, delivering such sensitive and potentially emotionally charged information is ethically and professionally unacceptable.

Other potential problems center on the technology itself. Interruptions in connectivity may interfere with the assessment process. This is especially true when assessment is performed live during a videoconferencing session. Further, without the use of a secure server and encrypted communications, electronic communications may be intercepted by a third party. Buchanan concluded that "online clinical tests are both desirable and dangerous. There is clearly great potential, but a lot of work must be done before this potential is realized. Only time and extensive research can tell us whether these instruments will become a useful tool in behavioral telehealth contexts."


Although many insurance plans will pay for second opinions, a 2004–05 Gallup Poll found that nearly half of Americans said they would never seek a second opinion when their physician "diagnoses a condition, prescribes a treatment, drug, or operation." Forty-one percent said they sometimes sought second opinions, and a scant 3% said they would always seek one. (See Figure 3.2.)

Women were more likely than men to assume responsibility for where their family members obtain medical care, and Gallup data as well as other research confirms that women visit physicians more often than do men. Rick Blizzard, Gallup's health and health care editor, opines that the frequency of physician visits affords women more opportunities than men to cultivate trusting relationships with their physicians. Still, women (47%) were more likely than men (42%) to say they always or sometimes seek a second opinion, and while 46% of women said they never seek a second opinion, more than half of men (52%) said they would never seek a second opinion. (See Figure 3.3.)

Educational attainment also is related to the propensity to seek a second opinion. Fifty percent of the survey respondents who were college graduates and 52% of respondents with postgraduate education said they always or sometimes seek a second opinion, compared with 37% of those with a high school education or less. (See Figure 3.3.)

Blizzard also observed that while it seems intuitively correct to assume that persons in poor health would be more likely to seek second opinions, Gallup Poll data revealed that respondents who rated their health as excellent or good (44%) were almost just as likely to seek second opinions as those who said their health was fair or poor (45%). (See Figure 3.4.)

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Diagnosing Disease: The Process of Detecting and Identifying Illness

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