Establishing clinically meaningful within-individual improvement thresholds for eight patient-reported outcome measures in people with relapsing-remitting multiple sclerosis

Abstract

Background: As disease-modifying therapies do not reverse the course of multiple sclerosis (MS), assessment of therapeutic success involves documenting patient-reported outcomes (PROs) concerning health-related quality of life, disease and treatment-related symptoms, and the impact of symptoms on function. Interpreting PRO data involves going beyond statistical significance to calculate within-patient meaningful change scores. These thresholds are needed for each PRO in order to fully interpret the PRO data. This analysis of PRO data from the PROMiS AUBAGIO study, which utilized 8 PRO instruments in teriflunomide-treated relapsing-remitting MS (RRMS) patients, was designed to estimate clinically meaningful within-individual improvement thresholds in the same manner, for 8 PRO instruments.

Results: The analytical approach followed a triangulation exercise that considered results from anchor- and distribution-based methods and graphical representations of empirical cumulative distribution functions in PRO scores in groups defined by anchor variables. Data from 8 PRO instruments (MSIS-29 v2, FSMC, MSPS, MSNQ, TSQM v1.4, PDDS, HRPQ-MS v2, and HADS) were assessed from 434 RRMS patients. For MSIS-29 v2, FSMC, MSPS, and MSNQ total scores, available anchor variables enabled both anchor- and distribution-based methods to be applied. For instruments with no appropriate anchor available, distribution-based methods were applied. A recommended value for meaningful within-individual improvement was defined by comparing mean change in PRO scores between participants showing improvement of one or two categories in the anchor variable or those showing no change. A "lower bound" estimate was calculated using distribution-based methods. An improvement greater than the lower-bound estimate was considered "clinically meaningful".

Conclusion: This analysis produced estimates for assessing meaningful within-individual improvements for 8 PRO instruments used in MS studies. These estimates should be useful for interpreting scores and communicating study results and should facilitate decision-making by regulatory and healthcare authorities where these 8 PROs are commonly employed.

Keywords: Patient-reported outcome (PRO); Relapsing-remitting multiple sclerosis (RRMS); Teriflunomide; Validation; Within-patient change threshold.