New WHO testing guidelines
As part of this broader global response to viral hepatitis, and to complement existing care and treatment guidance for HBV  and HCV , WHO has now developed guidelines on hepatitis B and C testing for low and middle-income countries (LMICs)  (Tables 2, 3, 4 and 5). In recognition of the need to substantially increase viral hepatitis testing to meet the 2030 elimination targets (particularly in low and middle-income countries), but also of the substantial cost to health budgets of increased testing, the guidelines take an evidence-based but pragmatic, low-cost approach. Their primary target audience are policy makers responsible for development of national hepatitis testing and treatment programmes in LMICs. A particularly challenging aspect in the guidelines’ development was the limited direct quantity and quality of evidence available to guide the development of recommendations  based on the use of the GRADE process. In addition, very few rapid diagnostic serological tests for hepatitis B surface antigen or hepatitis C antibody have undergone formal quality assurance approval process by WHO (pre-qualification) or another recognised stringent national regulatory programme.
The first group of recommendations focuses on who to test for chronic hepatitis B and C. There was a strong recommendation for focussed testing among people most affected by viral hepatitis B or C (defined as those who are either part of a population with higher seroprevalence (e.g. some mobile/migrant populations from high/intermediate endemic countries, some indigenous populations) or who have a history of exposures or high-risk behaviours for HCV infection (e.g. PWID, people in prisons and other closed settings, MSM and sex workers, partners, family members and children of HBV infected persons) as well as adults and children with a clinical suspicion of chronic viral hepatitis. The guidelines made a conditional recommendation that in settings with intermediate (≥2%) or high (≥5%) prevalence, all adults should have routine access to testing, with linkage to care and prevention services (Tables 2, 3, 4 and 5). The threshold used will depend on other country considerations and epidemiological context. In settings in which there are defined birth cohorts of older patients at higher risk for hepatitis C infection, the guidelines also recommend consideration of routine testing in birth cohorts. The strength of these recommendations was conditional, reflecting the more limited and lower-quality supporting evidence. Importantly, the guidelines recognise that testing should make use of existing community or health facility-based testing opportunities or programmes such as at antenatal clinics, HIV or TB clinics  (Tables 2, 3, 4 and 5). The guidelines provide illustrative examples of different testing service delivery models in different populations and settings.
The second group of recommendations addressed “how to test?” with respect to choice of assays (i.e enzyme immunoassays (EIA) that are generally performed in a laboratory setting compared to rapid diagnostic tests (RDTs) that can be undertaken within the community) and sequence of tests (ie. testing strategies). Although RDTs generally are slightly less accurate than EIAs, they may enhance access to testing in settings with poor access to laboratory testing and facilitate receipt of results and linkage to care and treatment. The trade-off between the small difference in test accuracy and the key goal to promote access to testing, means that on balance EIA was recommended as the preferred assay in settings where laboratory testing is available, especially for HBsAg where there is a wide variation in diagnostic performance of available RDT assays, and RDT recommended in settings with poor access to laboratory testing and/or in populations where access to rapid testing would facilitate linkage to care and treatment. The recommendation was graded “strong”, based on low/moderate quality of evidence  (Tables 2, 3, 4 and 5).
The need for a one or two-assay serological testing strategy was also addressed. Again, whilst a second confirmatory test would improve diagnostic accuracy, particularly in lower prevalence settings, this would incur additional complexity and costs. This led to the pragmatic recommendation that a single initial RDT or EIA was sufficient prior to a supplementary nucleic acid test (NAT) test for current viraemia. In low-prevalence settings (≤0.4%), confirmation of hepatitis B surface antigen (HBsAg) with a neutralisation step or a second and different RDT HBsAg assay should be considered due to the considerably improved positive predictive value (and hence reduced false positive rate) they confer. The strength of this recommendation was “conditional”, based on low quality of evidence  (Tables 2, 3, 4 and 5).
The use of a qualitative or quantitative nucleic acid test (NAT) to detect viraemia and inform assessment of an individual’s need for hepatitis B or C treatment was recommended (strong recommendation, moderate/low quality of evidence). With highly effective curative short course direct acting antiviral (DAA) treatment now available for hepatitis C infection, with need only to confirm presence or viraemia and cure, a qualitative test may be sufficient depending on the limit of detection. For hepatitis C, a core antigen test with comparable clinical sensitivity (and potentially a simpler test for some laboratories) was recommended as a potential alternative to NAT for diagnosis of viraemic infection (conditional recommendation, moderate quality of evidence). When assessing treatment response and test of cure for hepatitis C, a NAT test was recommended rather than an antigen test for which there is currently insufficient data  (Tables 2, 3, 4 and 5). Monitoring for hepatitis B was addressed in the previously developed WHO Hepatitis B Guidelines  and includes annual HBsAg and HBV DNA measurement.
The use of dried blood spots (DBS) specimens for HBsAg and anti-HCV antibody serology testing and HBV and HCV NAT was examined. Again, trade-offs were considered, specifically whether whether DBS testing would sufficiently increase the number of tests being performed to an extent that would offset the reduced sensitivity and specificity. DBS testing was recommended where there are no facilities or expertise to take venous whole blood specimens; for persons with poor venous access (e.g. people who inject drugs); or where RDTs were not available or their use was not feasible. It was recognised that a key limitation to the expanded use of DBS was that currently there are no manufacturers’ protocols for use of DBS samples with their commercial assays, or regulatory approval for their use with DBS samples. As a consequence the current use of DBS specimens would be considered “off-label”. The recommendation (conditional, with low/moderate quality evidence) highlights the need to strengthen our understanding of the benefits and limitations of using DBS  (Tables 2, 3, 4 and 5).
For testing to improve patients’ outcomes it is necessary that patients testing positive are linked to care and receive appropriate treatment. Recommended strategies to improve linkage to care following a positive serological test for hepatitis B or C include the role of peers and lay health workers, clinician reminders to prompt testing, integration of testing into single one-stop-shop facilities such as mental health or drug services, and on-site RDT testing with same-day results. However, specific evidence that following hepatitis testing, a support service or service structure improves linkage to care and treatment are limited so the recommendation was graded conditional with low/moderate quality evidence  (Tables 2, 3, 4 and 5).
These inaugural viral hepatitis testing guidelines represent an important first step on the road map for increasing access to hepatitis B and C testing and to support the elimination goal. It also provides general guidance to countries on how to implement the recommendations and strategically select testing approaches and services and organise their laboratory services.
A challenge has been the quantity and quality of data to inform the testing recommendations, and these guidelines highlight the evidence and research gaps and agenda for the future. This should help governments in their decision-making on how best to implement testing programs. Hopefully it will also encourage manufacturers to register and qualify their RDTs and DBS tests, making it easier for services to utilise them. Demonstration/implementation science projects are needed to further guide implementation at country and regional level according to country epidemic profile and health services context.
Elimination of hepatitis B and hepatitis C as public health threats by 2030 is a laudable and feasible goal. The WHO testing guidelines will inform elimination strategies at individual health services and at country and regional levels. In addition, they will provide impetus for the development of the low-cost, high-quality tests that are vital for meeting elimination targets.