In-field evaluation of Xpert® HCV viral load fingerstick assay in people who inject drugs in Tanzania

Abstract

Background Although novel hepatitis C (HCV) RNA point-of-care technology has the potential to enhance diagnosis in resource-limited settings, very little real-world validation of their utility exists. We evaluate the performance of HCV RNA quantification using the Xpert® HCV Viral Load Fingerstick assay (Xpert® HCV VL Fingerstick assay) as compared to the WHO pre-qualified plasma Xpert® HCV viral load assay among people who inject drugs (PWID) attending an opioid agonist therapy (OAT) clinic in Dar-es-Salaam, Tanzania. Methods Between December 2018 and February 2019 consecutive HCV seropositive PWID attending the OAT clinic provided paired venous and finger-stick samples for HCV RNA quantification. These were processed on-site using the GeneXpert® platform located at the Central tuberculosis reference laboratory. Results A total of 208 out of 220 anti-HCV positive participants recruited (94.5%) had a valid Xpert® HCV VL result available; 126 (61%; (95% CI 53.8-67.0) had detectable and quantifiable HCV RNA. 188 (85%) had paired plasma and finger-stick whole blood samples; the sensitivity and specificity for the quantification of HCV RNA levels were 99.1% and 98.7% respectively. There was an excellent correlation (R2=0.95) and concordance (mean difference 0.13 IU/mL, (95% CI -0.9 to 0.16 IU/mL) in HCV RNA levels between plasma samples and finger-stick samples. Conclusion This study found excellent performance of the Xpert® HCV VL Fingerstick assay for HCV RNA detection and quantification in an African-field setting. Its clinical utility represents an important watershed in overcoming existing challenges to HCV diagnosis, which should play a crucial role in HCV elimination in Africa.