The human immunodeficiency virus infection has become the greatest health crisis faced by the global community. It is an illness which can change the physical, mental and social well-being of an individual. According to the World Health Organization (WHO) guidelines, over 30 million people are living with HIV and an additional 7400 are added to this community every day. HIV is a disease, which is transmitted via sexual and blood contact. Since this infection can become fatal at a late stage which is known as AIDS, the early diagnosis and disease control play a crucial role. The diagnosis of HIV infection is made on tests carried out on body fluids such as blood, plasma etc.
Tests are performed to detect HIV antibodies, P24 HIV antigen and HIV nucleic acid in serum. Among them HIV antibody test is the most commonly used test to diagnose HIV infection because it is less expensive, less time consuming and can be performed in many laboratories easily. It is always important to understand the behavior of the virus when it enters the bloodstream to perform the test at the correct time because wrong timing of the test can lead to false negative and false positive HIV tests. Therefore the HIV diagnosis cannot be made after a single test and confirmatory tests must be carried out on all positive tests.
Enzyme-Linked Immunosorbent Assay (ELISA) which is also known as the rapid test is the most widely used technique to detect antibodies against HIV. The test is performed on a serum sample of the suspected individual. But it can be also performed on any blood fluid like saliva, urine or dried blood spot. There are many reasons which can give a false positive result in the rapid test for HIV infection. If the tests used in the diagnosis are susceptible to a cause for false positivity, a false positive diagnosis may result in devastating consequences. Causes of falsely positive HIV rapid test can be divided as biological and technical causes.
Elevated CD5+ B-lymphocyte Activation
Elevated CD5+ B-lymphocyte activation in the early immune response to any infectious disease antigens produces broad-spectrum antibodies that can cause non-specific and unpredictable cross-reactivity in serological testing. This cross-reactivity can result in a false positive HIV test. It has been discovered that human African trypanosomiasis, which is a helminthic infection modulates and stimulates immune activation and increase the risk of the false positive rapid test. It has been observed that there is an increased rate of false positive HIV test among the African population.
This observation has suggested that a genetic factor may be contributing to false positivity of the tests. Infections like tuberculosis, leprosy, malaria, dengue fever, Chagas disease, and hepatitis B & C are known to cause antibody cross-reactions in ELISA test in genetically susceptible individuals. Klebsiella, Chlamydia, Shigella, and Yersinia are some other infective organisms which can cause similar reactions and give rise to false positive HIV tests. Other viral infections like herpes simplex and influenza have been discovered as factors which can influence the true positivity of HIV test.
Recombinant HIV Antigen Used in Rapid Test
Furthermore, recombinant HIV antigen used in the rapid test can get contaminated with bacterial proteins like Escherichia coli during the synthesis process and can cause false positivity.
Specimen Mix-up and Wrong Labeling
Specimen mix-up and wrong labeling are possible errors which can occur during specimen handling in the health care system. Since the test results are given following a visually read rapid test, misinterpretation is a common scenario which can occur during the procedure. Weakly positive tests should not be recognized as positive, except in screening for blood donors. Therefore the technical staff should be well trained and experienced to improve the quality of test interpretation.
Pregnancy And Other Medical Conditions
Pregnancy is another well-known cause of false positive HIV test. Systemic medical conditions like systemic lupus erythematosus, rheumatoid arthritis, and chronic renal failure can also give rise to similar false positivity. There is some evidence of vaccination for tetanus and influenza that also has an effect on the HIV antibody detection test. There are recommended algorithms, which should be followed when performing tests to diagnose HIV infection. According to that, the diagnosis needs 3 positive tests from three tests which have different mechanisms of diagnosing the disease. Falsely positive HIV test results can be reported when this protocol is not followed correctly.
According to the diagnostic algorithm, positive HIV rapid test needs a confirmatory test. Usually, the western blot technique is used as this confirmatory test. A falsely positive rapid HIV test can be identified when the result becomes negative in the western blot confirmatory test. Since the illness can affect not only the patient, as well as his/her family you should pay utmost attention to the correct diagnosis of HIV infection. The social stigma about the disease can change the individual’s affairs with society and make life more miserable. So in conclusion, since HIV infection is a life-changing, fatal condition the false positive tests should be suspected promptly and further investigations should be carried out to exclude the diagnosis.
Dr. Chauturi is an experienced writer specializing in English language and Medical Sciences, and degree holder in Medicine, Bachelor of Surgery at University of Sri Jayewardenepura currently awaiting her internship.