The relative importance of severity and rarity criteria in health resource allocation: an umbrella review.

Objectives: The primary objectives of this umbrella review were to (a) quantify the relative importance, of "severity" and "rarity" criteria in health resource allocation; and (b) analyze the contextual factors influencing the relative importance. The secondary objective was to examine how "severity" and "rarity" criteria are defined.

Methods: Searches were carried out in PubMed and Embase to identify eligible systematic reviews. Quality appraisal of systematic reviews was undertaken. From identified systematic reviews, primary studies were extracted and further screened for eligibility. The inclusion of severity and rarity criteria and their respective weights in primary studies were examined. Descriptive and regression analyses were performed.

Results: Twenty-nine systematic reviews were screened, of which nine met the inclusion criteria. Primary studies included in these systematic reviews were retrieved and screened, resulting in forty articles included in the final analysis. Disease severity was more frequently considered (n = 29/40) than disease rarity (n = 23/40) as an evaluation criterion. Out of all cases where both were included as evaluation criteria, disease severity was assigned higher weights 84 percent of the time (n = 21/25).

Conclusions: Our review found consistent evidence that disease severity is more relevant and preferred to rarity as a priority-setting criterion albeit constraints in statistical analysis imposed by limited sample size and data availability. Where funding for rare diseases is concerned, we advocate that decision-makers be explicit in clarifying the significance of disease severity and/or rarity as a value driver behind decisions. Our findings also reinforce the relevance of disease severity as a criterion in priority setting.