In medicine, a diagnostic test is any kind of medical test performed to aid in the diagnosis or detection of disease. For example, such a test may be used to confirm that a person is free from disease, or to fully diagnose a disease, including to sub-classify it regarding severity and susceptibility to treatment. Companion diagnostics have also been developed to preselect patients for specific treatments based on their own biology, where such targeted therapy may hold promise in personalized treatment of diseases such as cancer.
Most diagnostic tests are conducted on the living, Some of the diagnostic tests are parts of a simple physical examination which require only simple tools in the hands of a skilled practitioner, and can be performed in an office environment. Some other tests require elaborate equipment used by medical technologists or the use of a sterile operating theatre environment. Some tests require samples of tissue or body fluids to be sent off to a pathology lab for further analysis. Some simple chemical tests, such as urine pH, can be measured directly in the doctor's office.
The validity of diagnostic test results produced in each laboratory is entirely dependent on the measures employed before, during, and after each assay. Consistency in the production of good results requires an overall program that includes quality assurance, quality control, and quality assessment.
Medical tests can be classified into three categories: