Thai version of the Functional Rating Index for patients with back and neck pain: Part II responsiveness and head-to-head comparisons.

OBJECTIVES: To examine responsiveness and estimate minimal clinically important difference (MCID) of the Thai version of Functional Rating Index (Thai FRI) and examine head-to-head comparisons of the Thai FRI and other questionnaires.

METHODS: This study related to validation of a questionnaire and head-to-head comparisons. Patients with low back pain (LBP) completed the Thai FRI, Roland-Morris (RM), modified Oswestry, and multilevel RM disability questionnaires. Patients with neck pain (NP) completed the Thai FRI and Neck Disability Index at the first visit and 2-week follow-up. Patients and therapists rated Global Perceived Effect Scales (GPES). Effect size (ES), standardized response mean (SRM), correlations between the GPES with changes in questionnaire scores, and area under receiver operating characteristic curve (AUC) were calculated. The MCID was also estimated.

RESULTS: Eighty-four patients with LBP and 52 patients with NP completed the Thai FRI. ES = 1.34 for LBP; 1.28 for NP, SRM = 1.32 for LBP; 1.20 for NP, correlation = 0.49 for LBP; 0.38 for NP, AUC = 0.83 for both groups. MCID = 11.5 for LBP; 12.5 FRI points for NP.

CONCLUSION: The Thai FRI demonstrated responsiveness with large ES. Its MCID ranged from 11.5 to 12.5 FRI points. The Thai FRI had comparable responsiveness to other questionnaires and was appropriate for use in the patients with back and/or neck pain.