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◦If the results remain indeterminate after one year, the person is considered to be HIV antibody negative. Pretest and posttest counseling services should be provided. Applications of ELISA 1.In medicine for clinical diagnosis such as: Tracking the spread of disease e.g. HIV, HBV, common cold, bird flu etc Detecting antibodies in blood sample for past exposure to disease e.g. HIV Detection of antigens e.g. p24, p120 2.In food industry Detection of potential food allergens Detection of toxins in food 3.Many other areas/fields Rapid diagnostic tests (RDTs) Basically involve antibodies testing Many individuals do not qualify for ART because they do not know their HIV status. It is important to know ones serostatus because: i.Clinical diagnostic purposes ii.It is the entry point for HIV prevention and care intervention iii.To protect blood supplies for donations iv.It identifies HIV-positive pregnant women for PMTCT v.Monitor disease trends in population Rapid tests are visual tests that do not require the ELISA Reader.
36 Compiled by BRcomrades printers from eLearning downloads. Copy rights reserved. These tests are available in smaller test packs and therefore, are suitable for a laboratory having smaller sample numbers. They are technically simpler to perform although most of them have sensitivity and specificity comparable to ELISA. The commonly employed rapid anti-HIV antibody tests are based on the principles of dot immunoassay, or particle agglutination such as gelatin or latex. Summary of characteristics of rapid HIV tests for testing And counselling programmes Accuracy High sensitivity >99% High specificity >99% High reproducibility* >98% ■ Specimen type Preferably for use on whole blood (fi nger-prick samples) for ease of collection and to avoid the need for centrifugation ■ Little laboratory equipment required ■ No constant electricity or water supply required ■ Easy to perform Little technical training required Few steps ■ Easy to interpret Visual interpretation of results, usually without equipment Stable end-reading point ■ Rapid <30 minutes ■ Easy to store Storage at room temperature for several weeks (provided there are no significant temperature fluctuations) Shelf-life 12 months or longer ■ Number of tests performed Suitable for individual and small volume testing, e.g. 1−40 samples per day■ Minimal waste and waste disposal ■ Low cost Mostly <US$ 1.0 for the initial screening
37 Compiled by BRcomrades printers from eLearning downloads. Copy rights reserved. ADVANTAGES OF RAPID TEST Rapid tests enable decentralization of HIV testing and counseling acceptability of HIV testing and counseling Short time to obtain test result Reduced cost Ease of performance and ease of interpretation of test results Minimal facilities for storage and shelf-life Flexibility in numbers of tests performed Reduction in occupational exposure risk Pediatric HIV Diagnosis