DIAGNOSTIC TESTING FOR COMMUNICABLE DISEASE

Dorland's Illustrated Medical Dictionary (24th edition, 1965) defines "diagnosis" as the determination of the nature of a case of a disease. In practice, diagnosis is a process of observation, examination, and consideration of the pertinent medical and personal history of the patient. Conclusions as to the cause of disease are drawn from those observations. For many infectious or communicable diseases, the recovery and isolation by a laboratory of the disease agent from a patient exhibiting signs and symptoms associated with that disease agent is considered to be diagnostic. Also, since patients make specific antibodies to disease agents they are exposed to, the measurement of significant amounts of antibodies in a patient that are specific to a disease agent may also be considered diagnostic.

The use of laboratory data and information becomes increasingly important when the symptoms of a particular disease are not unique, or are nonspecific in early stages of the disease. For example, coughing, sneezing, chills, fever, and headaches are characteristics of a number of respiratory diseases caused by viruses and bacteria. In circumstances such as these, the recovery, isolation, and identification of the disease agent, or the demonstration of specific antibodies to a disease agent by a laboratory, is the only means by which a final diagnosis can be made.

A major activity of public health agencies is the identification of a disease outbreak in a community and the implementation of appropriate disease control measures. Disease outbreak control measures, such as the administration of antibiotics, immune globulin, and vaccines; the temporary closure of public facilities; or the suspension of public activities are based on knowing what specific disease agent is affecting the community. In these cases the rapid and definitive identification of the disease agent by a laboratory is necessary for health officials to apply the appropriate control measures.

While public health agencies are principally concerned with the assessment of the health status of the community, diagnostic testing of an individual with a communicable disease is an essential part of that assessment. This is the basis for reporting certain important infectious diseases to the health department, and is a form of disease surveillance, another important public health activity.

Eric C. Blank

(see also: Assurance of Laboratory Testing Quality; Laboratory Services; Laboratory Technician; Practice Standards; Reference Laboratory )

Bibliography

Dowdle, W. R. (1993). "The Future of the Public Health Laboratory." Annual Review of Public Health 14:649–694.