ELISA is a medical diagnostic test that detects antibodies or antigens in a patient’s blood or urine sample. It is used for disease testing, virus testing, and drug testing. False positives can occur due to contamination or certain patient conditions.
An enzyme immunosorbent assay, or ELISA, is a type of medical diagnostic test used to detect whether a certain antibody or antigen is present in a patient. It can be useful for a number of different immunology-related purposes, such as disease testing and virus testing. For example, an HIV ELISA test may be administered to determine if a patient is infected with HIV antibodies. Additionally, ELISA tests are also sometimes used in testing for illegal drug use. An ELISA test can also help detect allergic reactions to food products such as nuts or dairy products.
During an ELISA procedure, a healthcare professional typically collects a blood sample from a patient. This is usually done by inserting a needle into a vein on the back of the patient’s hand or the patient’s inner elbow area. Alternatively, an ELISA test may allow for a urine sample. In each case, the collected sample is placed in a test tube or on a slide or test strip. The health care provider then sends the sample to a laboratory for analysis.
In the laboratory, technicians will determine whether the targeted antibody or antigen is present in the test sample. If a patient has a certain disease or condition, their sample will contain antibodies for that disease or condition. These antibodies will attach to antigens, which are used as binding agents in most ELISA tests.
The lab technician will clean up the test sample using a special test solution that washes away everything except the antigens or antibodies that adhere to the antigens. Next, the lab technician applies an enzyme solution to the test sample. If the sample changes color or gives any other indication, the target antibody or antigen is present in the test sample and the patient will test positive for the condition.
In general, an ELISA test is considered reliable within the immunology community. It is possible, however, for a patient who does not actually have the targeted infection to experience a phenomenon known as a false positive. A false positive occurs when a patient not infected with the target antibodies gives a positive result during the ELISA test.
False positives can occur for several reasons. For example, if a sample is contaminated or inadvertently switched in the laboratory, a false positive can result. Patients with haemophilia or hemodialysis or alcoholic patients with hepatitis are also more susceptible to false positives. Injection drug users and women who have had multiple pregnancies may also be more likely to get false positives.
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