Evaluation of the Aptima™ HBV Quant Dx assay for semi-quantitative HBV viral load from dried blood spots.

Background: The detection and quantification of hepatitis B virus (HBV) DNA from dried blood spots (DBS) is a major tool for chronic hepatitis B management in resource-limited settings. This strategy fits in perfectly with the hepatitis control plan promoted by the World Health Organization. However, few commercial methods are validated for viral load (VL) measurement on DBS.

Objectives: Our objective was to evaluate the performance of the HBV VL measurement of the Aptima™ HBV Quant Dx assay on DBS compared to plasma samples on the Panther® platform (Hologic).

Study Design: 266 whole blood samples for routine measurement were included. Five spots of 75 μL of whole blood were loaded onto a card before centrifugation and plasma settling.

Results: 149 samples were quantifiable and 117 were not detected. We achieved excellent linearity (r² = 0.994) over a wide range of measurements suitable for clinical practice, and a 95 % lower limit of detection (LLOD-95 %) at 2.65 log IU/mL (445 IU/mL). A good performance of this assay was observed for samples with HBV VL > LLOD-95 % and 100 % of samples were detected if HBV VL was above 2.95 log IU/mL. The correlation between the two matrices for quantitative VLs was good (r² = 0.978) with a very low bias (-0.002 log IU/mL).

Conclusion: The Aptima™ assay can properly detect and quantify HBV DNA in DBS, providing a satisfactory use in clinical monitoring and therapeutic decisions. DBS represents an excellent alternative to plasma, especially in resource-limited countries, while maintaining the performance and advantages of an automated technique.