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

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 10min at 56°C on a thermomixer, or incubated for 1h 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 35μL 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 (R=0.96) and SPEX at RT (R=0.97) procedures, with a constant negative offset of approximately 2.0logIU/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.