Dried blood spot samples: Optimization of commercial EIAs for hepatitis C antibody detection and stability under different storage conditions

This study was undertaken to optimize and compare the efficiency of two commercial EIAs for anti‐HCV detection (HCV Ab Radim, Pomezzia, Italy and ETI‐AB‐HCVK‐4 DiaSorin, Vercelli, Italy), in dried blood spot (DBS) samples. The long‐term stability of anti‐HCV on DBS samples stored at three environmental conditions was also evaluated at: 2–8°C, 20–25°C, and −20°C. Paired DBS and serum samples were obtained from individuals with or without anti‐HCV. The type of elution buffer, sample and conjugate volume, sample incubation time and cut‐off values were evaluated. For both EIAs, a larger sample volume was used, and the cut‐off value determined by the manufacturer was employed for Radim EIA; however, ROC curve analysis was used for the DiaSorin EIA. The sensitivity and specificity of Radim EIA on DBS were 97.5% and 99.5%, respectively, and of DiaSorin EIA were 88.9% and 98.9%, respectively. Accurate results were obtained for a period of 117 days using DBS samples stored at all storage conditions, but storage at −20°C resulted in the lowest variation among the absorbance values. Both EIAs demonstrated the same limit of detection (until dilution of 1:104 with estimated viral load of 3.1 × 10−1 UI/ml), but the Radim EIA was associated with the best performance because a low coefficient of variation was observed in the repetition and reproducibility studies. In conclusion, commercial EIAs can be optimized for anti‐HCV detection in DBS samples that are extremely stable at different conditions for more than 100 days. J. Med. Virol. 84:1600–1607, 2012. © 2012 Wiley Periodicals, Inc.