Five Years of HCV Dried Blood Spot Testing in At-Risk Populations and the Impact of Reduced Sensitivity on Missed Diagnoses.

BACKGROUND & AIMS: Achieving HCV elimination requires diagnostic strategies capable of reaching underserved populations who remain poorly accessed by conventional healthcare pathways. Dried blood spot (DBS) sampling enables decentralised testing, but concerns remain regarding its analytical sensitivity and the potential risk of missed diagnoses.

METHODS

We conducted a 5 year real-world implementation study of DBS-based HCV screening in France (2020-2024). DBS samples were collected in harm reduction centers and other community-based facilities and sent to Montpellier University Hospital for centralised analysis. We evaluated the diagnostic yield of DBS in routine practice and estimated the potential number of missed cases by comparing the DBS detection threshold with the distribution of plasma HCV RNA levels observed at diagnosis in untreated individuals.

RESULTS

The limit of detection (LOD) for HCV RNA on DBS was 1252 IU/mL, with a systematic underestimation compared with plasma measurements (mean bias -2.29 log10 IU/mL). Among 1552 individuals tested using DBS, 428 (27.6%) were HCV RNA positive, including five cases with no detectable HCV antibodies. DBS testing accounted for 56.4% of all HCV infections identified in our laboratory during the study period. Based on plasma viral load distributions at diagnosis, 2.7% of infections, corresponding to approximately 12 additional cases, were estimated to be missed due to low HCV RNA levels.

CONCLUSION

Despite a modest reduction in analytical sensitivity compared with plasma-based testing, the substantial public health benefits associated with increased testing coverage strongly outweigh this limitation and support the integration of DBS into HCV elimination strategies.