HIV diagnosis is made by either demonstrating the presence of virus or viral products (antigens), alternatively by detecting host response (antibodies) to the virus. Rapid diagnostic tests provide same-day results and are a good form of initial screening. However, confirmatory tests such as serological assays (eg ELISA) to detect anti-HIV antibodies or HIV p24 antigen, Chemiluminescence immunoassays (CLIA) or Nucleic Acid Amplification Test (NAAT) to detect HIV nucleic acids, need to be mandatorily performed. HIV infection can be detected with great accuracy using WHO prequalified tests.
An infected person, generally develops antibodies against HIV after 4-6 weeks of infection. During this asymptomatic period of seroconversion — when the body’s immune system has still not developed anti-HIV antibodies — the infected person can unknowingly transfer the HIV infection to others. There is a high possibility that a test done during these initial days does not reveal the true diagnosis. This is where the testing kit’s sensitivity, specificity and the analytical sensitivity for HIV p24 antigen becomes utmost important in order to eliminate any false reporting.
Following a positive diagnosis, the patient should be retested before they are enrolled in treatment and care to rule out any potential testing or reporting error.
In India, since NAAT testing is quite expensive and not practically available for small and medium lab setups, serological assays such as ELISA, are a more common diagnostic method for HIV. As an alternative to NAAT, combined fourth-generation assays for detection HIV antigen and antibodies simultaneously have been developed with high sensitivity and specificity.
HIV and TB — a dual challenge, molecular testing to the rescue
Not just HIV, tuberculosis has also been a matter of concern for India with 27 per cent of the TB patients globally residing in India. In 2016, 12 per cent of the people who enrolled for HIV care in India had active TB. So India has a herculean task at hand to ensure early diagnosis of HIV and TB.
Having said that it is important to note that there is in urgent need to reach out to the remote areas through primary health
care centres to create awareness and access to initial screening.
Technologic advances with HIV diagnostics continue to address outstanding and new issues associated with diagnosis and the monitoring of infection by providing more simplified, cost-effective and accurate testing throughout the world.
Senior president, Sales & Marketing, Transasia Bio Medicals