Introducing the four dimensions 4D migraine scale: A composite score proposal evaluating migraine severity and treatment efficacy

Background: Different parameters are currently used to evaluate migraine frequency and disability. We aimed to formulate a composite scale including the most relevant clinical measures to better evaluate the burden of migraine. Methods: To create the composite four dimensions 4D migraine scale, we selected the most commonly used outcome measures: monthly migraine days (MMDs), number of monthly acute medications (MAMs), pain intensity (by Numerical Rating Score, NRS) and Migraine Disability Assessment (MIDAS) Score. Each parameter was categorized in different levels: five for MMDs, seven for MAMs, five for NRS and six for MIDAS to cover the entire empirical range of each variable. First, the relative weight of each level per parameter was rated by 197 migraine patients and 118 headache experts using Conjoint Analysis. Secondly, we applied the 4D migraine score to a sample of patients treated with galcanezumab. We assessed its concurrent validity for the scale's single parameters and the Head Impact Test HIT-6, an external patient-reported outcome measure. Results: There was a substantial agreement between clinicians and patients about the weight of each parameter in terms of Relative Importance (RI). For both categories, MMDs were the most relevant attribute (RI: 34% for clinicians, 32% for patients) and pain intensity NRS the least important (RI: 14% vs 13%). Though marginally, MIDAS was more important than MAMs for patients (29% vs. 26%), while for clinicians the relevance of these two attributes was almost equal (26% and 27%). In terms of the utility assigned to each level, strong agreement was confirmed between clinicians and patients. According to the utilities implicitly attributed by participants to the chosen representative levels of the four parameters, four different statistical models were derived, allowing to compute utilities from all possible values of MMDs, MAMs, NRS and MIDAS and finally a unique 4D migraine score for every possible patient, ranging from 0 (without migraine) to 100 (with the most severe migraine). The 4D score was valid in terms of sensitivity to changes and showed concurrent validity with respect to HIT-6. Conclusion: The 4D migraine scale, based on the preference weights of both clinicians and patients, could be useful to fully quantify the migraine burden and the efficacy of a treatment.