New kit speeds HIV testing

Dipstick, an inexpensive and quick HIV test developed in the United States, is now being manufactured in India.

Published: Thursday 31 December 1992

-- A LOW-COST AIDS test is now being manufactured in India. The test, known as the HIV Dipstick, was developed by the Programme for Appropriate Technology in Health, a US-based, non-profit agency, and does not require very complicated equipment, refrigeration or technicians to operate it.

The human immunodeficiency virus (HIV) that causes AIDS cannot be detected in blood or body fluids. Present tests can only find the antibodies that are produced by the body in response to HIV. Most tests use viral protein as the antigen to detect the antibodies. Antigens are substances that cause the production of antibodies. For test kits, antigens can be produced by tissue culture or genetic engineering.

The Dipstick test uses synthetically produced antigen and can detect antibodies of HIV-1 and HIV-2 -- the two viruses known to cause AIDS. The Dipstick is a simple, comb-shaped plastic piece no larger than a credit card. The synthetic antigen is fixed on the teeth of the comb and washed with reagents. When the comb is dipped into an HIV-infected sample, the antibodies react to the presence of a foreign body and clot on the antigen. The comb is then incubated in a specific gold-based reagent that causes the antigen spot to turn red, indicating an HIV-positive result. The absence of a coloured spot means the sample does not contain HIV antibodies.

Unlike the ELISA test for AIDS commonly used in developed countries, the Dipstick test can be done at room temperature. The results are produced in less than 30 minutes, whereas the ELISA test can take up to 4 hours to complete. Moreover, a single Dipstick test costs Rs 15, compared to more than Rs 50 for the ELISA test.

In an independent assessment of the Dipstick test in Belgium, the World Health Organisation's Collaborating Centre on AIDS found it detected 99.5 per cent of the HIV-1 positive in the laboratory while in field tests, it identified all the positive samples. Developed with funding from the Canada-based International Development Research Centre and the Rockefeller Foundation in the US, the test is now manufactured in India by a Gujarat firm. Part of the technology-transfer cost was borne by the Australian International Development Assistance Bureau.

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