The Aptima® (Hologic) assay has 6-sigma performance, high concordance with the RealTime (Abbott Molecular) reference assay, and is user friendly and efficient, making it a good choice for laboratories that perform routine monitoring of HIV-1 viral loads, according to findings published in the Journal of Clinical Microbiology.
Identifying and confirming true HIV-1 virologic failure through assay testing is critical for managing patients, as imprecision in testing when viral loads are low (specifically at approximately the 50 and 200 copies/mL cutoffs) can allow development of significant clinical problems, such as a patient failing therapy but remaining on the regimen. In the current study, the performance of two new fully automated HIV-1 viral load assays, Aptima HIV-1 Quant Dx and Cobas® HIV-1 (Cobas 6800; Roche Diagnostics), were compared with RealTime m2000 assay, which has been established as the standard for this purpose.
The precision and accuracy of the assays were evaluated in a retrospective evaluation that used excess plasma material previously obtained from 4 individuals who tested positively for HIV (subtypes B, C, AE, and AG). Concordance between the assays was also determined using 1011 surplus clinical samples that had been drawn routinely and selected retrospective longitudinal samples from 7 patients currently being treated.
The investigators found that all 3 assays showed highly concordant results for individual clinical specimens (R values from Deming regression >0.98; average difference ≤0.2 log copies/mL) and from the retrospective longitudinal specimens obtains from the patients on treatment. Both Aptima and RealTime had similar high precision and met the 5-sigma criterion for the majority of specimens analyzed, across all labs and subtypes. Conversely, Cobas was less precise and missed the 5-sigma criterion for the majority of samples.
“In this [first analysis comparing Aptima, RealTime, and Cobas 6800 assays], results from Cobas appeared less reliable near the clinically relevant cutoff and should be interpreted with more caution in this context,” concluded the researchers.