Adapting reflex NAT recommendations for various country contexts Programmatic experience with hepatitis B clinic-based reflex testing is currently limited. Countries in different regions should consider incorporating routine reflex hepatitis C RNA and hepatitis B DNA NAT into their national testing guidelines and infrastructure. The adoption of laboratory-based reflex testing versus clinic-based reflex testing with POC NAT will depend on the current national testing infrastructure, reliance on centralized high-throughput laboratories, the available sample transport network and the location of testing and treatment services. Although a laboratory-based reflex testing strategy is more appropriate in settings with large testing volumes supported by extensive sample transport networks, clinic-based reflex sample collection for NAT may be a preferred testing algorithm for populations such as pregnant women in antenatal clinics, key populations (people who inject drugs and men who have sex with men) and migrants and refugees who receive health care in community-based settings or in primary care settings that may have limited access to full-range phlebotomy as well as laboratory services. Instead, clinic-based reflex testing with initial HBsAg RDT followed by reflex sample collection for HBV DNA testing for those antibody positive and then using clinic-based POC NAT testing devices may yield the greatest linkage to care for such populations. A mix of clinic-based and laboratory-based reflex testing strategies may be required to meet the needs of different populations or regions in a country. Key steps to initiate laboratory-based reflex NAT testing

• Train outpatient clinic phlebotomy and laboratory personnel on new procedures for collecting specimens and processing HBV DNA tests. If the local laboratory reflex testing protocol requires two specimens (to minimize the risk of contamination) and phlebotomists are used to only collecting one specimen for HBV testing, appropriate training and quality assurance systems are needed to sensitize phlebotomists to collecting and labelling two sample tubes.
• Update electronic laboratory order forms for HBsAg and HBV DNA testing to list reflexonly testing options and develop laboratory guidance for HBV DNA reflex testing. Electronic ordering systems are not necessary for reflex testing but can help to streamline the transition to a new clinical process.
• The laboratory process should be designed to preserve specimen integrity and limit risk of cross-contamination. Laboratory managers should assess the risk of cross-contamination for available testing platforms and develop procedures to minimize this risk. Using two tubes to minimize the risk of cross-contamination will require additional commodity, transport and storage costs.• Planning for additional costs as needed: additional tubes, transport and storage if two tubes are collected for HBsAg and HBV DNA testing.
• Laboratory-based reflex HBV DNA virological testing can be integrated with other strategies, such as clinic-based reflex testing, to meet the needs of different populations.
• Evaluating HBV laboratory-based reflex testing programmes: providing feedback to providers and laboratory managers for quality improvement.