Applying Diagnostic Network Optimisation analysis to inform the introduction of G6PD testing into Indonesia for improved treatment of relapsing malaria

Background: Radical cure for P. vivax and P. ovale malaria using 8-aminoquinoline drugs primaquine or tafenoquine can prevent relapse, but requires glucose-6-phosphate dehydrogenase (G6PD) screening due to the risk of haemolysis in G6PD-deficient individuals. This study aimed to provide an evidence-based framework to inform the optimal allocation and referral networks for G6PD testing devices in Indonesia. Methods: A diagnostic network optimisation (DNO) analysis using OptiDx was conducted across eight districts in Sumba, North Sumatra, and Central Java, representing high-, moderate-, and low-transmission settings. The maximum annual number of malaria cases from surveillance data between 2019 and 2022 was used as a proxy for testing demand. In baseline scenario, all public health facilities were equipped with G6PD testing devices. In referral scenario, devices were allocated only to selected facilities, with a maximum sample transport distance of 15 kilometres and sample delivery scheduled three times per week. Model outputs were reviewed with the National Malaria Control Programme (NMCP) to identify the optimal scenario, considering factors including implementation cost and accessibility. Results: Equipping 39% (30/76) of facilities in Sumba with G6PD testing devices could reduce total costs by nearly 30% in the first year and approximately 20% in subsequent years compared with the baseline, although the average referral distance increased from 4.48 kilometres to 9.8 kilometres. In North Sumatra, deploying 15 of 68 devices (19%) could reduce total costs by almost 60% in the first year and approximately 15% thereafter. Two health facilities (Puskesmas Padewatu in Sumba and Abdul Manan Hospital in North Sumatra) could experience workload increase exceeding 400 hours annually as referral facilities. In Purworejo, a single device placed at Puskesmas Mranti could enable on-site diagnosis for 56% of patients. Interpretation: The findings demonstrated that DNO can identify cost-efficient and equitable G6PD testing strategies to support safe radical cure and accelerate malaria elimination.