New Diagnostic Technique Could Improve Accuracy and Affordability of Early-Stage HIV Testing
A new blood screening technique known as "pooling" is able to accurately identify HIV infections in the early stages that are often missed by standard tests, according to a study appearing in today's edition of the Journal of the American Medical Association, Reuters Health reports. The pooling technique caught four cases of acute HIV infection missed by standard testing in a study of more than 8,000 people. Prior to the advent of pooling, HIV RNA PCR was the best way to test for early-stage HIV infection. However, the PCR test is expensive and has "limited" accuracy. During pooling, large numbers of samples can be screened by combining small amounts from up to 90 specimens in one large specimen to be screened for HIV. If the pool tests negative, all of the samples are clear. If the pool tests positive, the samples are then individually tested until the positive sample is isolated. The study's lead author, Dr. Christopher Pilcher of the University of North Carolina-Chapel Hill, noted that the pooling process improves on the accuracy of the PCR test because a sample will have been tested twice before it is definitively declared positive.
Cheaper Blood Tests Prove Effective, Could Provide Cost-Effective Option for Developing Nations
In related news, several inexpensive blood tests used to monitor HIV infection have been found to work just as well as their more expensive counterparts and could provide a cost-effective option for tracking HIV infection in patients in developing nations, Reuters Health reports. Two studies evaluating the effectiveness of inexpensive blood tests were presented Monday at the XIV International AIDS Conference in Barcelona, Spain. In one study, CDC researchers evaluated a technique known as panleucogating (PLG), which measures CD4+ T cells to determine the strength of a patient's immune system. The researchers compared PLG, which costs less than $5, with the standard $20 FACSCount test and found that the PLG results "correlated closely" with the FACSCount tests. The PLG test worked better than the other tests on samples of blood that had been taken three days prior to screening. In another study, Dr. Robert Downing, head of the CDC's laboratories in Uganda, evaluated a new test that measures blood levels of reverse transcriptase, an enzyme produced by HIV that correlates to viral load. The test, which costs $30, was compared with the standard RNA viral load test, which costs $150. Downing said that in preliminary experiments the new reverse transcriptase test "was as good as the standard assay" for measuring trends in viral load over time for patients on antiretroviral treatment. However, the new test did not detect HIV in two of the 13 specimens reported as having a high viral load (Pincock, Reuters Health, 7/8).