Deriving the optimal limit of detection for an HCV point-of-care test for viraemic infection: analysis of a global dataset

BACKGROUND & AIMS: Affordable point-of-care (POC) tests for hepatitis C (HCV) viraemia are needed to improve access to treatment in low and middle income countries (LMICs). Our aims were to determine the target limit of detection (LOD) necessary to diagnose the majority of persons with HCV eligible for treatment, and identify characteristics associated with low-level viraemia (LLV) (defined as the lowest 3% of the distribution of HCV RNA) to understand those at risk of being mis-diagnosed.

METHODS: We established a multi-country cross-sectional dataset of first available quantitative HCV RNA linked to demographic and clinical data. We excluded individuals on HCV treatment. We analyzed the distribution of HCV RNA and determined critical thresholds for detection of HCV viraemia. We then performed logistic regression to evaluate factors associated with LLV, and derived relative sensitivities for significant covariates.

RESULTS: The dataset included 66,640 individuals with HCV viraemia from Georgia (44.4%), Canada (40.9%), India (8.1%), Cambodia (2.6%), Egypt (1.6%), Pakistan (1.3%), Cameroon (0.4%), Indonesia (0.2%), Thailand (0.2%), Vietnam (0.1%), Malaysia (0.05%), and Mozambique (0.02%). The 97% LOD was 1,318 IU/mL (95% CI 1298.4, 1322.3). Factors associated with LLV were younger age 18-30 vs. 51-64 years (OR 2.56 95% CI 2.19, 2.99), female vs. male sex (OR 1.32, 95% CI 1.18, 1.49), and advanced fibrosis stage F4 vs. F0-1 (OR 1.44, 95%CI 1.21, 1.69). Only the younger age group had a decreased relative sensitivity below 95% at 93.3%.

CONCLUSIONS: In this global dataset, a test with an LOD of 1,318 IU/mL would identify 97% of viraemic HCV infections among almost all populations. This LOD will help guide manufacturers in the development of affordable POC diagnostics to expand HCV testing and linkage to care in LMICs.

LAY SUMMARY: We created and analyzed a dataset from 12 countries with 66,640 participants with chronic hepatitis C virus infection. We determined that about 97% of those with viraemic infection had 1300 International Units/mL or more of circulating virus at the time of diagnosis. While current diagnostic tests can detect as little as 12 International Units/mL of virus, our findings suggest that increasing the level of detection closer to 1300 would maintain good test accuracy and will likely allow for more affordable portable tests to be developed for use in low and middle income countries.