Jul 19, 2004
In some parts here, 40% of adults are infected with HIV and C subtype is the main one. Many do not know they are infected and there is a question if tests designed for B subtype are as accurate for C and some other rare subtypes.
I am sorry to ask a few questions, but no one seems to know the answers.I will be very grateful if you can help -
a. How sensitive are blood samples for ELISA tests to delays in processing specimens? In one of your answers last year, you talked about how delays in separating plasma and cells causes breakdown of antibodies and virus in whole blood (less sensitivity therefore?). Do the 99.8 % sensitivity numbers for ELISA's anticipate perfect handling of specimens?
b. Nutrition is a problem for many here - could that mean, if some have low numbers for chemicals or enzymes that are important for the ELISA to work as well, that the test is less reliable? (for example, maybe abnormally low alkaline phosphotase or B cells)....or is low normal enough for reliable ELISA's?
c. I live in a hot climate where the local Clinic stores blood specimens all day until they are sent to the laboratory at 5pm. Will the delays reduce sensitivity of ELISA?
d.Here, they sometimes use an ELISA with viral lysate from B subtype and other times may use one with synthetic peptides. Yet C is predominant in South Africa and Zimbabwe. Is the 99.8% sensitivity for B antibodies the same for C or is there some reduction the more the subtypes depart from B?
Response from Dr. Holodniy
a. this pertains more to viral load tests than to antibody testing. b. this should not affect the test. c. labs should be running quality control tests to make sure the tests in their hands are working properly. d. Many commercial tests are available that can adequate test for subtypes A and C.
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