Predictive value of the ultrasensitive HIV viral load assay in clinical practice

The aim of this study was to determine whether an HIV viral load of <50 cop ies/ml (c/ml), in the first available plasma sample to have shown a viral l oad of <400 c/ml, in patients on antiretroviral therapy, is correlated with longer term suppression of viral load (at <400 c/ml) compared to a viral l oad of 50-399 c/ml, and secondly, to compare the results obtained by ultras ensitive and standard viral load assays carried out on the same sample. A t otal of 98 HIV-positive patients on a nti retroviral thera py with a. viral load of <400 c/ml and at least one subsequent viral load measurement, were selected. For each patient, the first available specimen showing a viral l oad of <400 c/ml was tested using the Roche Amplicor ultrasensitive viral l oad assay, and patients were followed up subsequently for a median period o f 52 weeks. Whether patients achieved an ultrasensitive viral load (USVL) o f <50 c/ml or not made very little difference to the proportion of patients in each group showing continued response to treatment (52% vs. 45% respect ively). The only variable that was shown to significantly predict longevity of response was the number of antiretroviral drugs used. Secondly, a stand ard viral load of <400 c/ml but with a detectable signal above background l evels, was strongly predictive of a USVL of >50 c/ml. Overall, the findings suggest that the advantage in predictive value of the ultrasensitive over the standard HIV viral load assay, shown previously in clinical trials, may be limited in clinical practice. J. Med. Virol. 67:411-416, 2000. (C) 2000 Wiley-Liss, Inc.