A psychometric evaluation of the Musculoskeletal Health Questionnaire (MSK-HQ): validation and measurement invariance in inflammatory arthritis.

Objectives: The Musculoskeletal Health Questionnaire (MSK-HQ) is a patient reported outcome measure (PROM) co-produced for use across musculoskeletal diseases. This study analyses the validity, reliability, sensitivity to change and measurement invariance of the MSK-HQ in inflammatory arthritis (IA).

Methods: A total of 5106 patients recruited to the National Early Inflammatory Arthritis Audit (NEIAA) between May 2018 and March 2020 with a diagnosis of IA were included. Patients completed PROMs at baseline and 3 and 12 months alongside clinic visits. Convergent validity was assessed in relation to the HAQ-II, Patient Health Questionnaire 4 (PHQ-4) and 28-item DAS (DAS28). Construct validity was assessed using confirmatory factor analysis (CFA). Hierarchical tests for configural, metric and scalar invariance determined measurement invariance in item CFAs.

Results: The MSK-HQ total score correlated well with the HAQ-II (r = -0.79) and PHQ-4 (r = -0.66) and moderately with the DAS28 (r = -0.42). A unidimensional structure for the MSK-HQ was confirmed only when two items relating to illness perception were excluded. The MSK-HQ total score demonstrated good sensitivity to change. Reliability was high (α = 0.93). The minimum clinically important difference was 4 points across the IA subtypes. Significance was noted in tests of DIF for a few MSK-HQ items, but the level of bias was small.

Conclusion: This study provides evidence for the validity and sensitivity to change of the MSK-HQ in patients with IA, with a change of >4 points likely to be clinically meaningful. The MSK-HQ has high convergent and construct validity and is sensitive to change, providing a valuable tool for clinical care and research studies.