Diagnosis
Diagnosis
Diagnosis, from gnosis, the Greek word for knowledge, is the process of identifying a disease or disorder in a person by examining the person through a physical examination and studying the results of medical tests and laboratory and radiological techniques.
The diagnosis, in the field of medicine, begins when the patient is presented to the doctor with a set of symptoms or perceived abnormalities such as pain, nausea, fever, or other untoward feeling. Often the diagnosis is relatively simple, and the physician can arrive at a clinical conclusion and prescribe the proper treatment. At other times, the symptoms may be subtle and seemingly unrelated, making the diagnosis difficult to finalize and requiring laboratory work.
The diagnosis is based on data the physician obtains from three sources, the first being the patient. This includes the patient’s perception of his or her symptoms, medical history, family history, occupation, and other relevant facts. The physician then narrows the diagnosis with a second set of information obtained from the physical examination of the patient. The third source is the data obtained from medical tests, such as a blood test, x ray, or an electrocardiogram.
Patient information
The physician begins the examination by asking about the patient’s symptoms. The patient may be asked to describe the symptoms and how long he or she has been experiencing them. If the patient is in pain, information is collected about the location, type, and duration of the pain. Other symptoms that may be present but may not have been noticed by the patient must be explored.
The patient’s occupation may have a bearing on his or her illness. Perhaps he or she works around chemicals that may cause illness. A job of repetitive bending and lifting may result in muscle strain or back pain. A police officer or fire fighter may have periods of boredom interrupted by periods of stress or fear.
The physician must learn when the symptoms first appeared and whether they have worsened over time or remained the same in intensity. If the patient has more than one symptom, the physician must know which appeared first and in what order the others appeared. The doctor will also ask if the symptoms are similar to ones the patient has experienced in the past or if they are entirely new.
The medical history of the patient’s family also may be helpful. Some diseases are hereditary and some, though not hereditary, are more likely to occur if the patient’s parent or other close relative has had such a disease. For example, the person whose father has had a heart attack is more likely to have a heart attack than is a person whose family has been free of heart disease.
Personal habits, such as smoking or drinking large amounts of alcohol, also contribute to disease. Lack of exercise, lack of sleep, and an unhealthy diet are all involved in bringing about symptoms of disease.
The physical examination
In addition to exploring the patient’s clinical history, the physician will carry out a physical examination to further narrow the list of possible conditions. The patient’s temperature, blood pressure, and rate of respiration will be measured. He or she will be weighed and his or her height measured. The physician will use an otoscope to examine the eardrums and to look into the throat for signs of inflammation, infection, or other abnormal conditions.
The heart and lungs can be examined superficially using a stethoscope. Abnormalities in the heartbeat or in the functioning of the heart valves can be heard in this way, and the presence of water or other fluid in the lungs can be heard as noises called rales. The physician also can study the sounds made by the intestines by listening to them through the stethoscope.
Using his/her fingers, a technique called palpation, the physician probes the abdomen for signs of pain or an abnormal lump or growth. He/she also feels the neck, the axillary area (armpit) and other locales to locate any enlarged lymph nodes, a sign of an infection. Such probing also may bring to light the presence of a tender area previously unknown to the patient.
If the patient is complaining of an injury, the physician can carefully palpate around the injury to determine its size. He/she can bend an leg or arm to assess the integrity of the joint. Using other maneuvers, the physician can determine whether a ligament has been torn and if it may need surgical correction.
The laboratory examination
Having learned the patient’s clinical history and made his/her physical examination, the physician may then decide to submit specimens from the patient to a laboratory for testing. Fluids such as blood, urine, stomach fluid, or spinal fluid can be collected.
Basic laboratory tests of blood include a count of the number of white and red blood cells. An elevated number of white blood cells indicates an infection is present, but does not pinpoint the location of the infection. Blood also carries hormones and other components that are directly affected by disease or inflammation.
Far from the laboratory of the 1960s, the modern clinical laboratory is one of automation and high technology. Whereas before the laboratory technician was required to mix together the chemicals for each test, newer technology requires only that a blood specimen be placed in one end of a machine. The blood is carried through the machine, minute amounts of the chemicals are added as needed, and the results printed out. This technology also enables the measurement of blood or urine components in amounts much smaller than previous technology allowed—often at microgram levels. (A microgram is one millionth of a gram.) To measure such a minute amount, the chemistry involved is precise and the reading of the results is beyond the capability of the human eye.
Both blood and urine may contain evidence of alcohol, illicit drugs, or toxic substances that the patient has taken. Infectious organisms from the blood or urine can be grown in culture dishes and examined to determine what they are. Bacteria in blood or urine are often too sparsely distributed to be seen under the microscope, but bacteria in a blood specimen wiped across a plate of culture medium will grow when the plate is placed in an incubator at body temperature.
The physician also may want to obtain x rays of an injured area to rule out the possibility of a fractured bone. The presence of a heart condition can often be determined by taking an electrocardiogram (ECG), which measures the electrical activity of the heart. Changes in the ECG can indicate the presence of heart disease or give evidence of a past heart attack. CAT (computerized axial tomography) scans use x rays to produce images of one layer of hard or soft tissue, a procedure useful in detecting small tumors. Magnetic resonance imaging (MRI) uses radio waves in a magnetic field to generate images of a layer of the brain, heart, or other organ. Ultrasound waves are also sometimes used to detect tumors.
Physicians can collect other kinds of information by injecting substances into the patient. Injection of radiopaque liquids, which block the passage of x rays, allow x-ray examination of soft tissues, such as the spinal cord, that are normally undetectable on x-ray photographs. Metabolic disorders can sometimes be pinpointed using a procedure called scintigraphy, in which a radioactive isotope is circulated through the body. A gamma camera is then used to record the concentration of the isotope in various tissues and organs.
KEY TERMS
Culture medium— A substance that supports the growth of bacteria so they may be identified.
Invasive— A technique that involves entering the body.
Pathology— The study of changes in body tissues brought about by disease or injury.
other laboratory specimens can be obtained by invasive techniques. If the physician finds a suspicious lump or swelling and needs to know its nature, he or she can remove part of the lump and send it to the laboratory to be examined. The surgical removal of tissue for testing is called a biopsy. In the laboratory, the specimen is sliced very thin, dyed to accentuate differences in tissues, and examined under the microscope. This enables the physician to determine whether the lump is malignant (cancerous) or benign (noncancerous). If it is cancer, further tests can determine if it is the primary tumor or if it has grown (metastasis) as a result of being spread from the primary tumor. Other tests can determine what kind of cancer it is.
The method of actually looking into the body cavity used to mean a major surgical procedure called a laparotomy. In that procedure, an incision was made in the abdomen so the physician could look at each organ and other internal structure in order and determine the presence of disease or parasite. Now the laparotomy is carried out using a flexible scope called a laparoscope, which is inserted into the body through a small incision. The scope is attached to a television monitor that gives the physician an enlarged view of the inside of the body. The flexibility of the scope allows it to be guided around the organs, and a light attached to the scope helps the physician see each organ. In addition, the laparoscope is equipped with the means to collect biopsy specimens or suction blood out of the abdomen. Minor surgery can also be carried out to stop a bleeding blood vessel or remove a small growth from an organ.
Once the above steps the physician deems necessary have been carried out, he or she will then study the evidence collectively and arrive at a diagnosis. Once having determined the diagnosis, the physician can prescribe the proper treatment.
Larry Blaser