Comparison of the Abbott realtime human immunodeficiency virus type 1 (HIV-1) assay to the Cobas AmpliPrep/Cobas TaqMan HIV-1 test: workflow, reliability, and direct costs

Abstract

The Abbott RealTime human immunodeficiency virus type 1 (HIV-1) assay (ART) and the Cobas AmpliPrep/Cobas TaqMan HIV-1 test (CTM) are commercially available assays for quantification of HIV-1 RNA in plasma. We evaluated performance characteristics, workflow, throughput, reliability, and direct costs of these assays. Both assays yielded good correlation of quantitative results (r = 0.95) among clinical specimens, with a mean difference of -0.34 log(10) copies/ml. Testing of healthy donor plasma specimens yielded "target not detected" results by ART, with "HIV-1 RNA detected, <40 copies/ml" results for 3.3% (3 of 90 samples) of these specimens by CTM. Both the m2000sp/m2000rt (ART) and docked CAP/CTM96 (CTM) instrument systems were capable of operating with continuous, uninterrupted workflow. When daily maintenance and cleaning were included, ART and CTM run durations (5 h 52 min and 6 h 4 min, respectively) and hands-on times (53 min and 46 min, respectively) were similar for a run batch size of 24. While ART was more flexible in terms of run batch size, CTM required fewer user interventions and consistently produced higher specimen throughput rates at 8, 16, and 24 h. Assay run failure rates were 6.3% (1 of 16 runs) and 4.2% (1 of 24 runs) for ART and CTM, respectively (P = 1.000), with invalid specimen result rates of 1.0% (5 of 495 specimens) and 2.8% (11 of 399 specimens), respectively (P = 0.073). Direct reagent and consumable costs for each assay were comparable (difference of <10%). In selecting an assay for implementation, laboratories should consider how various assay and instrument features might impact laboratory operation and patient care.

FIG. 1.

Deming regression analyses and Bland-Altman plots of valid quantitative results for clinical plasma specimens. Graphs show comparisons of ART to CTM (A and B) (n = 87), CAM to CTM (C and D) (n = 81), and CAM to ART (E and F) (n = 75).

FIG. 2.

Assay workflow comparison between ART and CTM. Averaged hands-on and hands-off times are represented by the filled and open bars, respectively. Hands-on time for both assays includes all currently recommended instrument maintenance procedures necessary to start the first assay run of the day. For CTM, the hands-on time does not include a manual review of amplification growth curves for all clinical specimens in the assay run (see reference 16).