The impact of a co-payment on the cost-effectiveness of screening for diabetic retinopathy

Background: To determine the impact of a co-payment on the cost-effectiveness of systematic screening for diabetic retinopathy in Hong Kong (HK). Methods: An analysis was conducted from provider and societal perspectives. A Markov cohort model was used to determine the cost-effectiveness of screening with a co-payment of HK$60 (US$7.7) compared with free screening, with and without an assumption that the inverse care law (ICL) would operate in the presence of a fee as seen in our previous data. Results: From the provider perspective, the incremental cost-effectiveness ratio (ICER) of free versus pay systematic screening was HK$166 558 (US$21 354)/extra quality adjusted life year (QALY) gained assuming an effect of the ICL and free screening was always more cost-effective than pay screening when willingness to pay for a QALY was HK$124 488 (US$15 960) or above. Without an effect of the ICL, the ICER was HK$480 479 (US$61 600)/extra QALY gained. From the societal perspective, the ICER was HK$144 046 (US$18 467)/extra QALY gained with an effect of the ICL and HK$199 741 (US$25 608)/extra QALY gained with no effect. Conclusions: Free systematic screening was highly cost-effective from the societal perspective compared with screening with a small co-payment irrespective of the effects of the ICL. From the provider perspective, free screening was highly cost-effective if the ICL operates.