Testing for HIV now foolproof

The National AIDS Research Institute NARI,part of a consortium of five institutes that screen and evaluate HIV testing kits,has stringent measures in place to make sure test results are accurate.

A battery of tests and several checks later,a trained technician at Punes National AIDS Research Institute can wipe the sweat from his brow and positively say either a yes or a no to a persons HIV status. In the job for several years now,NARI is not only recognised as the countrys apex lab but has only recently received recognition from the National Accreditation Board for Testing and Calibration of Laboratories NABL this year.

The HIV serological laboratory works overtime to ensure that there are no mistakes,says Dr Ramesh Paranjape,Director,NARI. So much so that now any HIV testing kit that National AIDS Control Organisation NACO wants to purchase or a company wants to sell will have to be screened and evaluated by a consortium of five laboratories including NARI. In the last two months we have examined and tested as many as 35 HIV testing kits for their sensitivity and specificity, says Arun Risbud,a scientist at NARI.

The consortium of five laboratories has been developed with an aim to create parity between the four national reference laboratories including NIMHANS at Bangalore,NICED at Kolkata,NCDC and National Institute of Biologicals at New Delhi. NARI,along with the other labs,will conduct the evaluation and batch testing of diagnostic kits for various transfusion transmitted infection TTIs.

So far we have been depending on the World Health Organisation on quality control measures for evaluating test kits. We did not have our own mechanism to do so, says Paranjape. There have been reports in the past of faulty and substandard HIV test kits and this consortium has been developed to tackle such problems at the peripheral areas.

As part of the model quality control programme,an inter lab comparison of the results is done in the first week of each quarter as an additional check to assure quality. Once in the laboratory the disease is detected either by the presence of antibodies to the virus or by the detection of the virusits DNA and RNA. Three to five ml of the blood is collected in a clean screw-capped vial for the Enzyme- Linked Immunosorbent Assay ELISA test. When a serum sample tests positive to an ELISA,it is immediately repeated by a different system to confirm the diagnosis.

Results are assessed and compared with standard results,a performance score is developed and feedback is given to the participating laboratories. Nearly 100 samples are tested and evaluated at NARI every day. NARI has also started Early Infant Diagnosis test using the dried blood spot-PCR method.