Reimbursement decision making is based on a relative effectiveness assessment (REA), which may be combined with a cost-effectiveness assessment, by national Health Technology Assessment (HTA) agencies. These assessments are based on clinical data where new interventions are compared to the current standard of care, which may differ between countries. Since most pivotal trials only include a limited number of interventions, indirect treatment comparisons (ITCs) can be used to compare multiple interventions. The aim of this study was to evaluate the use of ITCs in HTA decision making in the Netherlands and England.

All pharmaceutical assessments published between 2015 and 2019 by the National Health Care Institute (ZIN) and the National Institute for Health and Care Excellence (NICE) were reviewed to determine whether an ITC had been used. For detailed analysis we included all assessments of ZIN using an ITC, and a random sample of assessments of NICE using an ITC (10 assessments per publication year).

Between 2015 and 2019 a total of 106 and 265 assessments were conducted by ZIN and NICE, respectively. Of these assessments 48 from ZIN and 150 from NICE included an ITC. The detailed analysis showed that pharmaceutical assessments including indirect comparative evidence led to the REA conclusion of similar therapeutic evidence in 57 percent of 48 assessments by ZIN and in 52 percent of 50 assessments by NICE. Reimbursement recommendations including indirect comparative evidence most often resulted in positive recommendations by ZIN (57% assessments), and in restricted recommendations by NICE (50% assessments). Different methods were employed to incorporate indirect comparative evidence, such as naïve ITCs and network meta-analysis.

Our results showed a significant variability in the use of ITCs between NICE and ZIN, which may contribute to differences in their recommendations. Further analysis will provide deeper insight in these differences and may provide suggestions for a clearer international guidance on the use of ITCs for HTA.