Psychometric analysis of the Neuro-QoL Fatigue in generalized Myasthenia Gravis (gMG) using data from a phase 3 trial.

Objective: To evaluate the psychometric properties of the Neuro-QoL Fatigue patient-reported outcome measure and its short form when used to assess fatigue in adults living with generalized Myasthenia Gravis (gMG).

Methods: Data from Vivacity-MG3 (ClinicalTrials.gov Identifier: NCT04951622), a double-blind placebo-controlled phase 3 study of nipocalimab enrolled 196 participants living with gMG were analyzed. Psychometric analyses of Neuro-QoL Fatigue scores (19-item version and short-form version) focused on data from Baseline and the 24-week double-blind interventional phase of the trial. Factor analytic and classical test theory (CTT) analyses were performed to investigate support for intended Neuro-QoL Fatigue score use, along with convergent and discriminant relationships, known groups analyses, and sensitivity to change analyses. Thresholds to define meaningful within-person change (improvement) over time were also investigated.

Results: The full form factor analytic analyses showed evidence that a unidimensional model adequately fits the data (TLI = 0.99, RMSEA = 0.07), CTT analyses showed high internal consistency (alpha = 0.95), and high test-retest reliability for stable participants (r = 0.92); similar results were observed for the short form. Both versions' scores were correlated with a variety of reference variables at expected levels, demonstrated the ability to differentiate between clinically meaningfully distinct groups, and were significantly correlated with changes in other reference variables. Analyses suggested 19-item and short-form score changes of 6.7 and 7.6, respectively, as showing meaningful improvement over time.

Conclusions: Results provided robust psychometric evidence that supports the use of Neuro-QoL Fatigue scores for assessing fatigue in adults living with gMG.