Performance Evaluation of the Aptima HIV-1 RNA Quant Assay on the Panther System using the Standard and Dilution Protocols

Abstract Background Currently, FDA-approved HIV-1 viral load (VL) assays use venipuncture-derived plasma. The Hologic Panther system uses 0.7 mL for the Aptima HIV-1 Quant Assay standard (APT-Quant-std) and dilution (APT-Quant-dil) protocols. However, smaller plasma volumes from fingerstick whole blood (FSB) collected in EDTA-microtainer tubes (MCT) could provide an easier sample collection method for HIV-1 VL testing. Objectives To evaluate the performance of the APT-Quant-std compared to the Roche CAP/CTM and Abbott m2000RT VL assays and an alternative APTQuant 1:7 dilution protocol, the latter using 100 μL of MCT-derived plasma from FSB. Study design Linearity was determined using commercial HIV-1 RNA plasma controls. Dilutions ranging 1.56-2.95 log10 copies/mL were prepared to determine the APT-Quant-dil Limit of Quantitation (LOQ) using Probit analysis. Specificity of APT-Quant-std was calculated using 326 HIVnegative samples. To evaluate agreement, 329 plasma specimens were tested with APT-Quant-std, CAP/CTM, and m2000RT. Forty-seven matched venipuncture and MCT-derived plasma specimens were tested with APT-Quantstd and APT-Quant-dil. Results Among the RNA controls, specificity was 99.69% for APT-Quantstd. The R2 values were 0.988 (APT-Quant-std/CAP/CTM), 0.980 (APT-Quantstd/ m2000RT), and 0.997 (APT-Quant-std/APT-Quant-dil). The APT-Quant-dil LOQ was estimated at 2.7 log10 copies/mL (500 copies/mL) (95%CI 2.62- 2.87). At 2.3 log10 copies/mL (200 copies/mL), the overall agreement was 91.0% for APT-Quant-std/CAP/CTM, 85.7% for APT-Quant-std/m2000RT, and 82.9% for APT-Quant-std/APT-Quant-dil. Quantified APT-Quant-std results were on average 0.2 log10 copies/mL higher than CAP/CTM and m2000RT and 0.14 log10 copies/mL higher than APT-Quant-dil. Conclusion APT-Quant showed similar performance compared to the CAP/CTM and m2000RT assays and remains sensitive and accurate using the dilution protocol.