Sensitivity and Specificity

Sensitivity and specificity are indications of the accuracy of a laboratory test. Most laboratory tests are ordered as part of a diagnostic process. The patient presents with a symptom that prompts the clinician to order a test. A laboratory test with poor sensitivity and/or specificity can lead to an inaccurate diagnosis due to the risk of missing a condition where it exists or producing a positive test result when the patient does not have a disease. A test that indicates that a person does not have a disease when the person has a disease is known as a False Negative (FN) while a test that indicates a person has a disease when the person does not have a disease is known as a False Positive (FP). Fortunately, the risk of an inaccurate test result is almost always balanced by other factors in the diagnostic process like symptoms, risk history, other test results and clinician experience. Besides being used to help with diagnosis, laboratory tests are also used for screening (testing for the presence of a disease before a person is symptomatic). When used for screening purposes, a test’s sensitivity and specificity are even more important.