Problems in the interpretation of HIV-1 viral load assays using commercial reagents

✍ Scribed by O'Shea, Siobhan; Chrystie, Ian; Cranston, Ross; Mullen, Jane; Corbett, Karen; Murphy, Gary; Parry, John V.; De Ruiter, Annemiek; Banatvala, Jangu

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 202 KB
• Volume: 61
• Category: Article
• ISSN: 0146-6615
• DOI: 10.1002/(sici)1096-9071(200006)61:2<187::aid-jmv3>3.0.co;2-8

✦ Synopsis

During routine monitoring of human immunodeficiency virus (HIV) viral load, two problems arose. First, a number of patients, the majority being African, were found to have low viral loads by the Chiron branched-chain DNA assay in conjunction with low CD4 + cell numbers. In order to determine whether this was due to failure of the branched-chain DNA assay to detect non-B subtypes of HIV, selected samples were subtyped and HIV RNA quantified by branchedchain DNA, NASBA, and the Roche Monitor RT-PCR assay. Twenty-eight (97%) of 29 Africans were infected with a non-B subtype of HIV and 15 (93.7%) of 16 non-Africans with subtype B. Twenty-three samples had a low viral load by branched-chain DNA, which was confirmed by the NASBA and RT-PCR assays. All three assays detected B and non-B subtypes with similar efficiency; NASBA failed to detect HIV RNA in a small number of non-B samples. Discrepancies between viral load and CD4 + cell numbers did not appear therefore to be related to subtype. Second, while quantification of HIV RNA was being conducted using version 2 of the branchedchain DNA assay (lower detection limit 500 HIV RNA copies/ml) the manufacturers had developed a more sensitive assay and a comparative evaluation was therefore conducted. In approximately 30% of samples the viral load was up to 10 times higher with the more sensitive assay. These experiences emphasise the importance of close collaboration between the clinic and the laboratory.