Evaluation of the Xpert HCV VL Fingerstick point-of-care assay and dried blood spot HCV-RNA testing as simplified diagnostic strategies among people who inject drugs in Catalonia, Spain.

BACKGROUND: Catalonia requires decentralized and simplified strategies for the diagnosis of viremic HCV infection among people who inject drugs (PWID). We aimed to perform a direct comparison of the diagnostic performance between two, single-step strategies for the screening and diagnosis of viremic HCV infection in PWID attending a drug consumption room (DCR) in Barcelona: i) on-site HCV-RNA testing using the point-of-care test (PoCT) Xpert HCV VL Fingerstick; and ii) on-site dried blood spots (DBS) collection for HCV-RNA testing at the laboratory (in-house assay). Additionally, we aimed to assess participants' preferences in receiving HCV-RNA testing results and feasibility of same-day delivery of PoCT results. METHODS: The real-world, clinical performance of these two strategies was established in comparison with the reference method (HCV viral load testing with the Xpert HCV Viral Load assay at the laboratory from venous plasma collected at the DCR). HCV genotypes/subtypes and HIV status were also determined by sequencing and serology, respectively. A questionnaire including preferences regarding the delivery of test results was administered. RESULTS: The prevalence of HCV-RNA was 63.0% (of which 25.8% were co-infected with HIV). The RNA-PoCT showed a sensitivity of 98.4% for detectable viral loads (>4 IU/mL) and of 100% for quantifiable viral loads (≥10, ≥1000 and ≥3000 IU/mL). For the DBS-based assay, a sensitivity of 93.7% was obtained for detectable viral loads, 96.7% for the quantifiable ≥10 IU/mL threshold, and 98.3% for both the quantifiable ≥1000 and ≥3000 IU/mL thresholds. No significant differences were detected between the sensitivity values of these two strategies, and the specificity was 100% in both cases. Half of the participants preferred to receive the HCV-RNA result on the same day, and 80% of participants received their RNA-PoCT results on the same day. CONCLUSIONS: Both the HCV-RNA PoCT and the DBS-based assay are highly reliable tools for the simplified diagnosis of viremic HCV infection among current PWID. These strategies allow for on-site sample collection and delivery of test results, facilitating decentralized care in harm reduction services.

Reliable resolution of ambiguous hepatitis C virus genotype 1 results with the Abbott HCV Genotype Plus RUO assay.

Accurate subtyping of hepatitis C virus genotype 1 (HCV-1) remains clinically and epidemiologically relevant. The Abbott HCV Genotype Plus RUO (GT Plus) assay, targeting the core region, was evaluated as a reflex test to resolve ambiguous HCV-1 results in a challenging sample collection. 198 HCV-1 specimens were analysed with GT Plus (38 specimens with and 160 without subtype assigned by the Abbott RealTime Genotype II (GT II) assay targeting the 5'NC and NS5B regions). Sanger sequencing of the core and/or NS5B regions were performed in 127 specimens without subtype assignment by GT II, with "not detected" results by GT Plus, or with mixed genotypes/subtypes. The remaining GT Plus results were compared to LiPA 2.0 (n = 45) or just to GT II results if concordant (n = 26). GT Plus successfully assigned the subtype in 142/160 (88.8%) samples. "Not detected" results indicated other HCV-1 subtypes/genotypes or mismatches in the core region in subtype 1b. The subtyping concordance between GT Plus and either sequencing or LiPA was 98.6% (140/142). Therefore, combined use of GT II and GT Plus assays represents a reliable and simple approach which considerably reduced the number of ambiguous HCV-1 results and enabled a successful subtyping of 98.9% of all HCV-1 samples.