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Oct 3, 2022 · Diagnostic tests are tools used to confirm or rule out a condition or disease. They can be invasive or non-invasive and help you and your doctor make informed decisions about your health.
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Diagnostic testing is used to detect, identify, monitor, screen, and predict diseases and conditions in the body. Learn about the 4 purposes and 11 common types of diagnostic tests, such as X-rays, MRI, CT scan, ultrasound, and blood tests.
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diagnosis, the process of determining the nature of a disease or disorder and distinguishing it from other possible conditions. The term comes from the Greek gnosis, meaning knowledge.
The diagnostic process is the method by which health professionals select one disease over another, identifying one as the most likely cause of a person’s symptoms. Symptoms that appear early in the course of a disease are often more vague and undifferentiated than those that arise as the disease progresses, making this the most difficult time to make an accurate diagnosis. Reaching an accurate conclusion depends on the timing and the sequence of the symptoms, past medical history and risk factors for certain diseases, and a recent exposure to disease. The physician, in making a diagnosis, also relies on various other clues such as physical signs, nonverbal signals of distress, and the results of selected laboratory and radiological and other imaging tests. From the large number of facts obtained, a list of possible diagnoses can be determined, which are referred to as the differential diagnosis. The physician organizes the list with the most likely diagnosis given first. Additional information is identified, and appropriate tests are selected that will narrow the list or confirm one of the possible diseases.
Traditionally, diagnosis has been defined as the art of identifying a disease from its signs and symptoms. Formerly, few diagnostic tests were available to assist the physician, who depended on medical history, observation, and examination. In the 20th century there occurred numerous technological advances in medicine, which resulted in the development of a wide variety of diagnostic tests and new techniques to image tissues. These developments significantly improved the ability of doctors to make accurate diagnoses.
In the 5th century bce, at the time of the Greek physician Hippocrates, there arose significant interest in medicine and personal hygiene. The Greeks recognized the salubrious effects of bathing, fresh air, a good diet, and exercise. The ancient Romans also recognized the influence of these factors on health and even made significant advances in supplying and purifying water and in improving sanitation. Today, a balanced diet, clean air and water, and exercise continue to be emphasized as important factors for maintaining health. The ancient Greeks also introduced the notion that illness resulted from an imbalance between the four humours of the body: blood, phlegm, yellow bile, and black bile. They emphasized the value of observation, including bodily signs and excretions. However, the focus was more on predicting the outcome of an illness (i.e., prognosis) and less on its diagnosis. A physician’s reputation depended on accurate prognostic skills, predicting who would recover and who would die or how long an illness would last.
Hippocrates is credited with establishing the ethical basis of the physician’s behaviour, and graduating physicians still recite the Hippocratic oath. His writings document the value of objectively evaluating all aspects of the patient’s symptoms, diet, sleep patterns, and habits. No finding was considered insignificant, and physicians were encouraged to employ all their senses—sight, hearing, smell, taste, and touch—in making a diagnosis. These principles hold just as true today.
Galen of Pergamum (129 ce–c. 216) is considered the most influential physician after Hippocrates because of his extensive studies in anatomy and physiology. His voluminous writings rendered him the ultimate authority in these fields until the 16th century. As the first experimental neurologist, he described the cranial nerves and the sympathetic nervous system. He observed the structural differences between arteries and veins. One of his most important demonstrations was that the arteries carry blood, not air, as had been taught for 400 years. However, many of his views contained fallacies, which remained unchallenged for centuries. His description of the heart and its chambers and valves, in which he contended that blood passes from the right to the left ventricle by means of invisible pores in the interventricular septum, delayed the discovery of blood circulation for 14 centuries. The true nature of the circulation of blood was not recognized until the early 17th century, when English physician William Harvey published his findings in Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus (1628; Anatomical Exercise on the Motion of the Heart and Blood in Animals, or simply De Motu Cordis).
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Diagnosis is the process of determining the nature of a disease or disorder and distinguishing it from other possible conditions. Learn about the definition, types, history, and tests of diagnosis from Britannica, the online encyclopedia of science and medicine.
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Learn the meaning of diagnostic as an adjective and a noun, with synonyms, examples, and word history. Diagnostic tests are used to identify or distinguish a condition or a feature.
A medical test is a procedure to detect, diagnose, or monitor diseases or conditions. A diagnostic test is a test to confirm or determine the presence of a disease in a suspected individual. Learn about different methods, purposes, and examples of diagnostic tests.
