Estimating hospitalization costs for Health Technology Appraisals (HTA) in England: a systematic literature review and best practice framework.

Aims: Reporting of hospitalization cost data for the National Health Service in England evolved substantially in the past decades which may have led to inconsistency in capturing the average cost of hospitalizations in appraisals of new health technologies. Our aim was to systematically review the estimation of hospitalization costs in appraisals for the National Institute for Health and Care Excellence (NICE) and the Joint Committee on Vaccination and Immunisation (JCVI), to identify potential heterogeneity and its drivers. A case study was used to explore the impact of alternative cost estimates on economic evaluations.

Methods: Systematic review of past NICE appraisals and published economic evaluations to inform the JCVI. Hospitalization cost data reported in each appraisal were extracted and separately re-calculated to inform descriptive analysis and linear regression. Deterministic sensitivity analysis was performed on an existing cost-effectiveness model of pneumococcal disease in adults, and a best practice framework was developed to support standardization of cost estimation in future appraisals.

Results: Length of stay (LoS) was accounted for in 4/118 (3.38%) currency codes across 29 appraisals. LoS and adjustment for complication and comorbidity score were key drivers of differences between cost estimates. There was a statistically significant negative average cost difference of -£1,235 (reported cost < calculated cost) for when accounting for LoS or not. On average, the range of reported costs overestimated hospitalization costs at minimum by £1,511 and underestimated these at maximum by £6,566, suggesting high levels of heterogeneity. In the case study, using spell costs resulted in estimating greater cost savings with the new technology which became dominant compared to the standard of care.

Conclusions: Results show high heterogeneity in the estimation of hospitalization costs across appraisals in England over the past decade. More detailed HTA guidance may potentially increase consistency among appraisals of new health technologies.