Hidden treasures and secret pitfalls: Application of the capability approach to ParkinsonNet

In the Netherlands, The largest health technology assessment (HTA) program funds mainly (cost-) effectiveness studies and implementation research. The cost-effectiveness studies are usually controlled clinical trials which simultaneously collect cost data. The success of a clinical trial typically depends on the effect size for the primary outcome, such as health gains or mortality rates. A drawback is that in case of a negative primary outcome, relevant other (and perhaps more implicit) benefits might be missed. Conversely, positive trials can contain adverse outcomes that may also remain hidden. The capability approach (developed by Nobel Prize winner and philosopher Sen) is an instrument that may reveal such "hidden treasures and secret pitfalls" that lie embedded within clinical trials, beyond the more traditional outcomes. Here, we exemplify the possible merits of the capability approach using a large clinical trial (funded by the HTA program in the Netherlands) that aimed to evaluate the ParkinsonNet concept, an innovative network approach for Parkinson patients. This trial showed no effects for the primary outcome, but the ParkinsonNet concept tested in this study was nevertheless met with great enthusiasm and was rapidly implemented throughout an entire country, and meanwhile also internationally.We applied the capability approach to the ParkinsonNet concept, and this analysis yielded additional benefits within several capability domains. These findings seems to substantiate the claim that richer policy debates may ensue by applying the capability approach to clinical trial data, in addition to traditional outcomes.