Abstract and Introduction
Achieving global elimination of hepatitis C virus requires a substantial scale-up of testing. Point-of-care HCV viral load assays are available as an alternative to laboratory-based assays to promote access in hard to reach or marginalized populations. The diagnostic performance and lower limit of detection are important attributes of these new assays for both diagnosis and test of cure. Therefore, our objective was to determine an acceptable LLoD for detectable HCV viraemia as a test for cure, 12 weeks post-treatment (SVR12). We assembled a global data set of patients with detectable viraemia at SVR12 from observational databases from 9 countries (Egypt, the United States, United Kingdom, Georgia, Ukraine, Myanmar, Cambodia, Pakistan, Mozambique) and two pharmaceutical-sponsored clinical trial registries. We examined the distribution of HCV viral load at SVR12 and presented the 90th, 95th, 97th and 99th percentiles. We used logistic regression to assess characteristics associated with low-level virological treatment failure (defined as <1000 IU/mL). There were 5973 cases of detectable viraemia at SVR12 from the combined data set. Median detectable HCV RNA at SVR12 was 287,986 IU/mL. The level of detection for the 95th percentile was 227 IU/mL (95% CI 170–276). Females and those with minimal fibrosis were more likely to experience low-level viraemia at SVR12 compared to men (adjusted odds ratio AOR = 1.60 95% confidence interval [CI] 1.30–1.97 and those with cirrhosis (AOR = 1.49 95% CI 1.15–1.93). In conclusion, an assay with a level of detection of 1000 IU/mL or greater may miss a proportion of those with low-level treatment failure.
Chronic hepatitis C virus (HCV) infection is a major cause of progressive liver disease and associated morbidity and mortality globally. In 2021, there were an estimated 58 million persons with a chronic infection, with a disproportionately high burden in low- and middle-income countries. Short-course curative direct-acting antiviral (DAA) regimens have transformed opportunities for treatment scale-up and elimination.[1–4] In 2016, the World Health Organization (WHO) launched the Global Health Sector Strategy for elimination of viral hepatitis as a public health threat, with ambitious targets for elimination of HCV including a 90% reduction in new infections and a 65% reduction in HCV-related mortality by 2030.[5,6]
In order to meet the 2030 global targets for HCV elimination, there is a need to substantially scale-up access to testing and treatment, with simplified service delivery models and diagnostic innovations to expand access. A key step in the care cascade is the use of HCV viral load assays to confirm presence of viraemic infection, and then a test of cure following treatment. The 2017 WHO viral hepatitis testing guidelines recommended a laboratory-based PCR Nucleic Acid Amplification Testing (NAAT), or a core HCV antigen assay with comparable clinical sensitivity, as preferred strategies for diagnosis of viraemic HCV infection, and laboratory-based PCR assays as a test of cure at SVR12.[9,10] Point-of-care HCV viral load assays are now available as an alternative to laboratory-based NAAT assays to promote access, especially in hard to reach or marginalized populations. A previous multi-cohort analysis examined the distribution of HCV viral load at diagnosis in 66,640 individuals from 12 countries and established that 97% had a viral load greater than 1318 IU/mL and 95% had a viral load greater than 3,311 IU/mL. The key laboratory-based assays (Abbott Real time HCV PCR, Alinity m HCV RT-PCR, Abbott Real time HCV PCR) have an analytical sensitivity or LloD of between 5–15 IU/mL, and key PoC assays: HCV RNA PoC GeneXpert assays are 10 IU/mL for venous blood,[12,13] or 100 IU/mL using fingerstick capillary blood. All these assays are therefore acceptable for diagnosis of HCV viraemic infection.
Currently, the European Association for the Study of the Liver Diseases, IDSA-AASLD HCV guidance panel, all recommend a minimum LLoD of 1000 IU/mL for HCV diagnosis, but none yet specify minimal test characteristics for test of cure.[14,15] While some small studies have examined the distribution of viral load at end of treatment—including a cohort of eight patients from the United States, a cohort of 14 patients in Germany and 330 treatment failures in an analysis of 34 phase 2/3 clinical trials. The latter study in clinical trials identify that 97% had a viral load >10,000 IU/mL 12 weeks post-treatment, and just 0.9% of patients had a viral load less than 1000 IU/mL (77, 405 and 680 IU/mL). To date, there have been no real world, global analyses of distribution of viral load in those with detectable viraemia at SVR12.
Our primary objective was to determine the LLoD for an HCV RNA assay to detect 90%, 95%, 97% and 99% of treatment failures at 12 weeks post-treatment in a large multi-cohort data set, and to assess the characteristics associated with low-level viraemia (<1000 IU/mL) at SVR12. These findings will help inform global policy as well as guide manufacturers as to whether existing platforms and assays meet requirements for their use both in diagnosis and as a test of cure, and for future development of testing technologies.
J Viral Hepat. 2022;29(6):474-486. © 2022 Blackwell Publishing