IMPLICATIONS OF USING EFFECTIVENESS INSTEAD OF EFFICACY ON THE COST-EFFECTIVENESS OF BIOLOGICS IN RHEUMATOID ARTHRITIS: A MULTI-STUDY SENSITIVITY ANALYSIS

  

Purpose: Randomized controlled trials (RCT) show greater benefit for biologics compared to observational studies in rheumatoid arthritis (RA).  However, it is unclear how using observational data can change RCT-based cost-effectiveness analyses (CEA) results.   

Methods: We identified nine RCT-based CEAs of biologics compared to nonbiologics that were published between 2000 and 2006.  We used the published sensitivity analysis results to calculate each study's input effect size (IES) for each input parameter, defined as percent change in incremental cost-effectiveness ratio (ICER) due to one percent change in an input from the baseline, and calculated average IES values across all studies.  Similarly, we calculated the mean RCT-based input values that were used in these studies.  Next, we located observational-based (OBS) estimates for these inputs from the National Data Bank for Rheumatic Diseases.  We calculated percent deviation of OBS from RCT estimates as: 100%*(OBS-RCT)/RCT.  Finally we calculated the predicted percent change in ICER when observational estimates are used instead of RCT estimates as: OBS % deviation * IES.   

Results: The IES and RCT-based inputs values were generally similar across all RCT-based CEAs. However, the values of the observational data were different from the RCT-based model estimates.  Overall, using observational data for six screened inputs increased the reported ICER from the RCT-based CEAs by 100%.  The most important input was the initial improvement in disability after receiving biologics (48% increase in ICER).  Second was the disability/utility conversion used to calculate quality of life from disability level (35% increase in ICER).    

Conclusions: Using observational-based estimates for several common inputs instead of RCT-based estimates doubled the reported ICER, causing biologics to appear less cost-effective than reported.  To our knowledge, this is the first attempt to systematically reconcile the impact of using observational data instead of RCT results on the CEA of biologics in RA.