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Alternative specimens - whole blood, oral fluid and urine

Is urine or saliva feasible to use as a source of HIV detection?

Tests are currently available for anti-HIV testing using urine and saliva specimens. However, the level of antibodies in these specimen types is lower than serum or plasma. Therefore, rigourous sample collection conditions, testing procedures, result validation and interpreation must be followed.

Window period

What is the "window-period" and how long is it?

This is the time between original infection with HIV and the appearance of Detectable antibodies to the virus, normally a period of about 14-21 days.

Simple / Rapid tests

What is a Simple/Rapid test?

Simple/Rapid tests are designed for use where a preliminary screening test result is required and are especially useful in resource-limited countries

  • High quality, easy-to-use tests for use in resource poor settings.
  • Tests based on agglutination, immuno-dot, immuno-chromatographic and/or immuno-filtration techniques.
  • Quick and easy to perform – 10 minutes to 2 hours – and require little or no additional equipment.
  • Are designed for use with individual or a limited number of samples, which make them more economical then ELISAs in low throughput laboratories.
  • Possibility to store at room temperature for extended period of time.
  • Same-day results provide timely treatment interventions.

What is the difference between a ELISA and a Simple/Rapid test

ELISAs are highly sensitive and specific, and are able to detect HIV-1/ HIV-2 and variants. They require sophisticated equipment that must be regularly maintained, a constant electricity supply and skilled technicians. They are really not suitable for small laboratories, but for testing large numbers of samples per day, as well as in blood banks or for surveillance studies. The Simple/Rapid tests are better for emergency testing, and in smaller laboratories with low numbers of tests per day.

Confirmatory assay

What is a confirmatory assay?

Confirmatory Assays are used to confirm whether specimens found reactive with a particular screening test contain antibodies specific to the virus they have been tested for.

  • Expensive tests, first generation tests have proven to be prone to producing large numbers of indeterminate results.
  • LIAs ( Line immune-assays ) have been developed which in general produce fewer indeterminate results.
  • Studies have shown that combinations of ELISAs or Simple/Rapid assays can provide results as reliable as the confirmatory assays at a much lower cost.

ELISA tests

What is an ELISA test?

Enzyme-Linked Immunosorbent Assays (ELISAs) are the most widely used type of assay. They have evolved from viral lysate tests to tests containing recombinant protein and synthetic peptide antigens:

  • They have high sensitivity and specificity.
  • ELISAs are designed specifically for screening large numbers of specimens at a time, making them suitable for use in surveillance and centralized blood transfusion services.
  • As ELISAs require sophisticated equipment and skilled technicians to perform the tests, their use is limited to certain circumstances.

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CMLF News Issue #7
27th January 2016