Evaluation of the COBAS® AmpliPrep/COBAS® TaqMan® HCV Test v2.0 for HCV viral load monitoring using dried blood spot specimens

- The two methods used to test HCV viral load using DBS generated comparable results.
- Heating and shaking incubation was comparable to incubation at room temperature.
- High correlation observed between results from plasma and either DBS methods.
- Offset between DBS and plasma results can be fixed with a correction factor.

This study evaluated the use of dried blood spot (DBS) for HCV viral load quantification using the COBAS® AmpliPrep/COBAS® Taqman® HCV Quantitative Test v2.0 (CAP/CTM HCV v2), and compared two different procedures for preparation of DBS samples with a Specimen Pre-Extraction (SPEX) reagent (either heated [SPEX with SH] for 10 min at 56 °C on a thermomixer, or incubated for 1 h at room temperature [SPEX at RT]) against the standard plasma input. Whole blood specimens from 48 patients with chronic HCV infection and Whatman® 903 Protein Saver Cards were used to prepare 35 μL DBS. An aliquot of plasma was spun and frozen from each draw. Mean DBS viral load results were compared to the corresponding results from plasma. Correlation between DBS to plasma was linear for both SPEX with SH (R2 = 0.96) and SPEX at RT (R2 = 0.97) procedures, with a constant negative offset of approximately 2.0 log10 IU/mL between whole blood DBS without any adjustments and plasma results. After volume corrections, the mean offset to plasma decreased to −0.39 and −0.36 for the two procedures, respectively. The study demonstrated the use of DBS for HCV viral load correlates well with plasma with a constant offset.