Comparison of Three Different FDA-Approved Plasma XXXX RNA Assay Platforms Confirm the Virologic Failure Endpoint of 200 copies/mL Despite Improved Assay Sensitivity.

@entity1 @entity2858 @entity73108 @entity177 @entity6500
UNASSIGNED: Discrepancies between @entity2858 RNA results assayed by different FDA-approved platforms have been reported. Plasma samples collected from 332 randomly selected clinical trial @entity1 during second year of antiretroviral treatment were assayed with 3 FDA-approved platforms: UltraSensitive Roche Amplicor Monitor, @entity6500 [Monitor], Abbott RealTime @entity2858 Test/m2000 [Abbott] and Roche TaqMan @entity2858 Test, v2.0 [TaqMan]. Samples from 61 additional @entity1 with confirmed @entity2858 RNA >50 c/mL during trial follow-up were also included. Endpoints were @entity2858 RNA quantification  <= vs. >50 c/mL at an individual sample level (primary) and determination of confirmed @entity177 ( @entity177 ) from longitudinal samples. 389 @entity1 had results obtained from all assays on at least one sample (median=6). Proportions of results >50 c/mL were 19% [Monitor], 22% [TaqMan] and 25% [Abbott]. Despite indication of strong agreement (Cohen's kappa: 0.76-0.82), Abbott was more likely to detect @entity2858 RNA >50 c/mL than Monitor (matched pair odds ratio [mOR]=4.2; modified Obuchowski p<0.001) and TaqMan ( @entity73108 ; p<0.001); TaqMan was more likely than Monitor (mOR=2.6; p<0.001). Although strong agreement in classifying @entity177 across assay comparisons (kappa: 0.75-0.92), at a 50 c/mL threshold, differences in the probability of @entity177 classification (in the same direction as primary) were apparent (all McNemar's p<0.007). At a 200 c/mL @entity177 threshold, no differences between assays were apparent (all p>0.13). Despite strong agreement among assays, significant differences were observed with respect to detecting @entity2858 RNA >50 c/mL and identifying @entity177 at the 50 c/mL threshold. This has important implications for the definition of @entity177 in clinical trials and clinical practice.
