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9. The opposite party no.3 submitted that the High Level Committee on enquiry also confirmed that the complainant had CD4 count of 189 which is suggestive of full blown up case of AIDS. On enquiry conducted at different levels the High Level Committee come to the conclusion that the same was due to human error and not due to wilful negligence of the Red Cross Blood Bank. It is also not brought to the notice of the committee that no test of HIV was ever conducted on the complainant. Out 1000 test results done using ELISA technique, among healthy individuals, about 3 may be false negatives and therefore the very high predictive value of the test is the reason why it is recommended and that is the reason why a negative test result can be taken as conclusive evidence that the individual does not have HIV. The opposite party no.3 further submitted that as per the ELISA test done on the donors, they were proved to be negative for HIV. The incubation period or window period for HIV infection to mature into AIDS is anywhere from 10-15 years depending on the immune response of the individual concerned and that it may not possible for an individual to be affected by AIDS within a period of 1 to 4 weeks from the date of the alleged infection through blood transfusion. There is no chance of HIV infection maturing into full blown AIDS as indicated by CD4 count within such a short time.

ELISA The enzyme-linked immunosorbent assay (ELISA), or enzyme immunoassay (EIA), was the first screening test commonly employed for HIV. It has a high sensitivity.

In an ELISA test, a person's serum is diluted 400-fold and applied to a plate to which HIV antigens have been attached. If antibodies to HIV are present in the serum, they may bind to these HIV antigens. The plate is then washed to remove all other components of the serum. A specially prepared "secondary antibody" an antibody that binds to human antibodies is then applied to the plate, followed by another wash. This secondary antibody is chemically linked in advance to an enzyme. Thus the plate will contain enzyme in proportion to the amount of secondary antibody bound to the plate. A substrate for the enzyme is applied, and catalysis by the enzyme leads to a change in color or fluorescence. ELISA results are reported as a number; the most controversial aspect of this test is determining the "cut-off" point between a positive and negative result.

Interpreting antibody tests ELISA testing alone cannot be used to diagnose HIV, even if the test suggests a high probability that antibody to HIV-1 is present. In the United States, such ELISA results are not reported as "positive" unless confirmed by a Western Blot.

The ELISA antibody tests were developed to provide a high level of confidence that donated blood was NOT infected with HIV. It is therefore not possible to conclude that blood rejected for transfusion because of a positive ELISA antibody test is in fact infected with HIV. Sometimes, retesting the donor in several months will produce a negative ELISA antibody test. This is why a confirmatory Western Blot is always used before reporting a "positive" HIV test result.

Rare false positive results due to factors unrelated to HIV exposure are found more often with the ELISA test than with the Western Blot. False positives may be associated with medical conditions such as recent acute illnesses and allergies. A rash of false positive tests in the fall of 1991 was initially blamed on the influenza vaccines used during that flu season, but further investigation traced the cross-reactivity to several relatively non-specific test kits. A false positive result does not indicate a condition of significant risk to health. When the ELISA test is combined with Western Blot, the rate of false positives is extremely low, and diagnostic accuracy is very high (see below).