Abstract
Background
Dried blood spots (DBS) are a reliable tool to diagnose viremic HCV infection. We evaluated the clinical performance of a DBS-based molecular assay for the assessment of cure and reinfection after on-site treatment at a harm reduction centre (HRC). Genotyping from DBS samples was also assessed to discriminate reinfection from treatment failure.
Methods
People who inject drugs (PWID) from an ongoing microelimination pilot at the largest HRC in Barcelona were included in the study. HCV-RNA detection from DBS collected after treatment (with follow-up at 12, 36 and 60 weeks) was compared with a molecular point-of-care test using finger-stick blood (GeneXpert). Baseline and follow-up DBS samples were genotyped by NS5B sequencing or commercial real-time PCR.
Results
Among treated patients, 193 follow-up DBS samples were tested. The DBS-based assay showed 100% specificity (129/129), and sensitivity ranged from 84.4% to 96.1% according to different viral load cut-offs (from detectable to 3000 IU/mL). Sensitivity as test of cure (follow-up 12) ranged from 85.1 to 97.4%. Among the 64 patients with recurrent viremia, 10.9% had low viral loads (≤1000 IU/mL); HCV genotyping allowed us to classify 73.5% of viremic cases either as reinfection or as treatment failure.
Conclusions
DBS samples are useful to assess cure and differentiate reinfection from relapse after HCV antiviral treatment in the real world, facilitating decentralization of treatment and post-treatment follow-up in PWID. However, a fraction of patients presented with low viral loads, limiting viremia detection and genotyping in DBS and, therefore, repeat testing is recommended.
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