Azrin Syahida Abd Rahim, Safurah Jaafar, Zukarnain Zakaria, Don Ismail Mohamed, Abd Rahim Mohamad
Probabilistic sensitivity analysis demonstrated that protocol 2 maintained favorable screening cascade efficiency across plausible operational scenarios. The lower incremental cost-effectiveness ratio in Sarawak suggests potential equity advantages in higher dropout settings. Illustrative willingness-to-pay thresholds of MYR 10-50 per additional carrier detected were explored for scenario interpretation rather than as normative policy thresholds. These findings support future prospective pilot evaluations and health technology assessment to inform screening implementation decisions.
OBJECTIVES: Malaysia's National Thalassemia Screening Program uses multivisit sequential testing (protocol 1), with a dropout rate of 20%, disproportionately affecting rural and underserved populations in Sabah and Sarawak. Protocol 2 proposes 3-tier testing from a single retained blood sample, eliminating visit-based dropout. Previous deterministic evaluation demonstrated favorable incremental cost per carrier detected but did not quantify parameter uncertainty.
METHODS: Probabilistic sensitivity analysis was conducted using 2018 administrative data covering 65 990 students in Sabah and Sarawak. Monte Carlo simulations (10 000 iterations) assigned probability distributions to all parameters: gamma distributions for costs (15% coefficient of variation) and beta-binomial for dropout rates. Cost-effectiveness acceptability curves estimated probabilities across willingness-to-pay thresholds of MYR 10-50 per additional carrier detected. Scenario analyses tested protocol 2 dropout rates ranging from 0.5% (base case) to 5% (pessimistic).
RESULTS: Mean probabilistic incremental cost-effectiveness ratios matched deterministic estimates (Sabah: MYR 20.8; Sarawak: MYR 10.3) with narrow 95% credible intervals (Sabah: 18.7-23.2; Sarawak: 9.2-11.5). At MYR 25-50 thresholds, protocol 2 has a > 91% probability of cost-effectiveness in Sabah and ∼100% in Sarawak. Under pessimistic 5% dropout scenarios, probabilities remained ≥70%, indicating substantial implementation tolerance.
CONCLUSION: Probabilistic sensitivity analysis demonstrated that protocol 2 maintained favorable screening cascade efficiency across plausible operational scenarios. The lower incremental cost-effectiveness ratio in Sarawak suggests potential equity advantages in higher dropout settings. Illustrative willingness-to-pay thresholds of MYR 10-50 per additional carrier detected were explored for scenario interpretation rather than as normative policy thresholds. These findings support future prospective pilot evaluations and health technology assessment to inform screening implementation decisions.