Pooling samples for hepatitis C RNA detection

Despite the negative impact of the COVID-19 pandemic on elimination of hepatitis C virus (HCV), the use of mass testing for SARS-CoV-2 might represent a glimmer of opportunity to increase HCV diagnostic capacities. Processing SARS-CoV-2 diagnostic tests has created an enormous workload for laboratories worldwide and has resulted in decreased processing of many other tests, such as those for HCV infection. Diagnosis of an active HCV infection is the necessary first step set by WHO as a key target to reach elimination. We propose a diagnostic strategy to overcome this challenge and to contribute to increasing the diagnostic capacity of clinical laboratories.

In many countries, sample pooling strategies have already been used for molecular screening of HCV RNA in blood banks and transfusion centres.¹ The strategy of pooling samples for diagnosis and only in cases of positive results doing an individual analysis was introduced by Dorfman in 1943,² and has shown its usefulness in the diagnosis of different infectious agents, including SARS-CoV-2.³

Here, we present proof of concept that a pooling strategy for HCV RNA might allow for the identification of patients with chronic HCV with excellent sensitivity performance. We tested two commercially available diagnostic tools (CAP CTM HCV v2.0 and the COBAS 6800 system, Roche Diagnostics GmbH, Mannheim, Germany) to determine their sensitivity through the ability to detect one positive HCV sample within a different number of pooled samples (ranging from 10 to 1 000 000 samples). Both tests were able to identify a positive sample when pooled in up to 10 000 samples (appendix).

Implementing a pooling strategy to increase diagnostic capacities for the elimination of HCV has some challenges, which include determining a pool size that maintains the maximum precision in the analysis and having appropriate laboratory technology for grouping and reporting results. Our results show that a plausible pool size in Spain, with an estimated prevalence of chronic HCV infection of 0·22%,⁴ would be 100 samples. This size allows for the detection of a single positive sample in a pool that is within the detection limit of commercial RNA assays, and also within the detection limit of core antigen (2000 international units per mL).⁵ Given current market prices, the price of pooled testing for HCV RNA could be €0·30 per sample for a pool sample size of 100. Consequently, by substantially improving cost-effectiveness, this strategy enables and provides the necessary sustainability for large scale HCV testing, including universal or age-based screening.

In summary, the strategy of pooling samples for the diagnosis of active HCV infection has numerous advantages that can be implemented and scaled up with the aim of eliminating HCV as a public health threat by 2030.

FG has received grants or contracts from ViiV Healthcare, Merck, Gilead, AbbVie, Seegene, Roche, and Werfen; payment or honoraria for lectures, presentations, speakers bureaus, manuscript writing, educational events, support for attending meetings, and travel grants from ViiV Healthcare, Roche, Merck, Gilead, AbbVie, Qiagen, Hologic, Seegene, and Werfen. All other authors declare no competing interests.