in medicine, the process of identifying a disease and designating it with accepted medical terminology— that is, making a diagnosis. The science of the methods of making a diagnosis is called diagnostics.
Diagnosis is based on the thorough and systematic study of a patient that includes (1) anamnesis—purposeful questioning concerning the complaints, history of the condition, and history of the life of the patient, (2) physical examination (inspection, palpation, percussion, auscultation), testing of visual and auditory acuity and reflexes with special devices, testing of the range of movements in the joints, and so forth; (3) analysis of the results of laboratory tests of blood and various excretions (feces, urine, sputum, pus, and so forth); X-ray examinations: graphic methods—recording on paper or film the movements of the heart (cardiography), blood vessels (sphygmography), and so forth; electrodiagnostic studies (electrocardiography, electroencephalography, and so forth); endoscopy—inspection of the interior of certain organs (for example, the stomach and urinary bladder) using special optical instruments; biopsy—the study of small pieces of tissue excised from the patient or of material obtained by puncturing bone marrow and lymph nodes with a special needle. In certain diseases, important diagnostic data are obtained with radioactive isotopes (radioisotopic diagnosis). Bacteriological and serological (using serum) methods are very important in diagnosing infectious and allergic diseases. In order to make a diagnosis in difficult cases, physicians sometimes resort to an exploratory operation, so that they may examine and study local changes directly.
In order to identify a disease, it is generally necessary to find a fairly large number of symptoms and combinations of symptoms and to determine their intensity. Since different diseases may share the same symptoms (for example, headache, fever, vomiting), differential diagnosis is used. The starting point is usually the selection of the most characteristic, prominent, and positively known (pathognomonic) symptom. The disease is compared with others that show a similar symptom. Less commonly, the diagnosis is made by excluding similar diseases.
To avoid the errors caused by insufficient medical experience, especially in diagnosing rare diseases, attempts were made starting in the 1950’s to make diagnoses with the help of computers, using symptoms (detected by the physician) whose significance in various diseases was calculated beforehand. Development of this approach (cybernetic medicine) is impeded by the difficulties encountered in evaluating symptoms quantitatively and by the imperfect classification of diseases.
In making a diagnosis, the physician attempts to find the cause of the disease and its accompanying diseases and complications and to assess the severity of the functional disorders (functional diagnosis). He also takes into account the particular physiological characteristics of the patient. Thus, a diagnosis must reflect the characteristics that distinguish a given patient from other patients with the same disease. An early, accurate, and maximally concrete diagnosis facilitates well-considered and efficacious therapy and often makes it possible to forecast possible variations in the course of the disease.
A pathologicoanatomical diagnosis is made post-mortem by a specialist (pathological anatomist) who bases his diagnosis on the study of the findings of the autopsy and on the chemical and microscopic analysis of tissues in comparison with the results of studies made while the patient was living. Pathologicoanatomical diagnosis is of value is finding and analyzing inaccuracies in diagnoses made during life; it is also used in forensic medicine.
V. I. ZAITSEV