Duffy Testing to Benefit Children's Population Health: A Cost-Effectiveness Analysis

The Duffy null phenotype is reported in approximately 1 in 10 Americans and results in absolute neutrophil counts (ANC) that are 40-50% lower than most institutional reference intervals. Misinterpretation of normal ANC values for this population leads to avoidable diagnostic testing and referrals. We aimed to evaluate the economic value of serologic Duffy testing vs no testing obtained alongside other recommended blood work at 9-12 months of age, employing a Markov cohort design incorporating all levels of currently practiced diagnostic neutropenia workups across scenario analyses. The analysis was conducted from a US societal perspective over a lifetime time-horizon across all accepted willingness-to-pay thresholds. The primary outcome was the incremental net monetary benefit (iNMB) in USD per quality-adjusted life-year (QALY). Duffy testing was favored in the base-case and all scenario analyses with iNMB ranging from $2.18 to $92.77 per-child tested for Duffy status. The cost of Duffy serological testing, the cost of the neutropenia workup, and the prevalence of low ANC were the three parameters with the greatest variation that affected the iNMB. Probabilistic analyses showed that universal testing was favored in 100%, 100%, 100%, 95%, and 100% of 10,000 iterations in the base-case, full workup, annual follow-up, minimal workup, and targeted testing scenarios. The Duffy null prevalence threshold required for universal testing to be cost-effective was 7.6%, 1.6%, 1.3% and 9.0%, respectively, and 4.9% for targeted testing. At these thresholds, universal serologic Duffy testing would align with cost-effective implementation in at least 20 states in the United States today.