Viral load as universal screening device
Aug 10, 1998
I recently underwent HIV testing. The window period was thrown out of the window, so to speak, as it has been 9yrs since the possible exposure. I tested at 3mos back in 90, and recently with Home Access and at a community blood drive. The ELISA and antigen tests were performed. To my knowledge, a viral load was not perfomed. What does 99.9% mean. You comment that viral load testing is fool proof. Why are ELISA and other screening tests still used if people have HIV and are negative on these tests. My concern is that a possible infection may go unnoticed in me by having these tests, and not a viral load. My M.D found no reason to test me as she stated my risk was so long ago and no health problems thus far. I have battled reccurent yeast infections and the FDA warning always makes me take notice. These types of infections ARE related to HIV infection. My M.D. says" no" to this. Anyway, how can I trust my negative results after 3 of them, I'm still not 100% sure. Do M.D.s consider negative ELISAs conclusive most of the time? The RED CROSS must trust them as they have almost no infections passed in the blood supply now. And they state the times infection occurs is during the window period. Also, how often do labs goof-up on results? Wow, I think I'm done. Thankyou
Response from Dr. Holodniy
You raise many important issues regarding testing strategies. The testing algorithm in place today has been around since the antibody tests were available (1985). The sensitivity (how good the test is at being positive when a person has the disease) and the specificity ( how good the test is in being negative when the person does not have the disease) are extremely important in determining the performance and FDA approval. It was recognized early that serial (several tests separated by time) HIV antibody tests were necessary to rule in or rule out the disease because of the time it took for antibody development. And that this was variable between people. The blood bank people have used this test for years to screen blood. A few years ago,it was recognized that antibody testing might miss early HIV infection and so blood is also now screened with p24 antigen, which can be detected in early infection before antibodies develop. Viral load tests have only been available for wide spread use for the last 3 years. As such, we don't have the number of years and hundreds of thousands of test experience in early infection like we do for antibody testing. The companies knew they could get approval faster for therapy monitoring or prognosis, than they could for diagnosis. My speaking about the numbers and tests comes from personal experience as well as reading what has been published on the subject. In all the acute infection studies to date, viral load tests are positive in all patients (USA and European studies)at time 0(first day they come for testing after exposure and infection. Using viral load to screen is also much more costly than using antibody or p24 antigen testing ($200 vs. $20-40/test). Three negative serial antibody tests now from an exposure 9 years ago, makes HIV infection extremely unlikely. Almost all MDs would come to this same conclusion. The ElISAs are very, very reproducible. If 3 tests from 3 different blood samples are negative, I personally would belive those results. Good Luck. MH
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