OBJECTIVES: The aims of this study were to a) identify published cost-effectiveness studies regarding bariatric surgery versus conventional treatment for obesity and overweight, b) assess their reporting quality, c) assess their transferability to Switzerland, and d) to adapt transferable cost-effectiveness results to Switzerland.

METHODS: A systematic literature search was performed in MEDLINE, Embase and other databases. Two reviewers independently undertook the screening, extraction of studies, assessment of reporting quality utilising the Consolidated Health Economic Evaluation Reporting Standards, assessment of transferability, and adaptation of cost-effectiveness results. Adaptation of cost data was performed in three steps: correction for different levels of resource utilisation, for different prices of healthcare services, and for changes in level of resource utilisation and prices over time.

RESULTS: Fifteen studies (Europe, the United States and Australia) fulfilled criteria for numerical adaptation of incremental cost effectiveness ratio (ICER) results to Switzerland. Adapted ICERs for patients with body mass index (BMI) >35 kg/m indicated a cost-saving (dominant) situation or showed ICERs of CHF 8,000-44,000 per quality adjusted life years (QALYs) gained for bariatric surgery versus conventional treatment. Adapted results for patients with BMI <35 kg/m showed ICERs of CHF 3,000-50,000 per QALY gained for bariatric surgery versus conventional treatment. Procedure-specific differences showed that gastric bypass appeared better than gastric banding in terms of benefits, but was more expensive.

CONCLUSIONS: Nearly all studies found bariatric surgery to be cost saving or cost-effective, compared to conventional treatment. Differences were due to approaches to the modelling of effectiveness (in terms of duration of BMI changes and dependent effects on morbidity, mortality) costs, time horizon, population studied, exact type of intervention studied, and possibly other unidentified reasons. The adaptation strategy described may be useful for individual countries in which financing or capacity for economic analyses is scarce.