Psychometric properties of a modified version of the Roland-Morris disability questionnaire (M-RMDQ).

BACKGROUND Chronic pain can be associated with limitations in patient function. Assessment of pain-related limitations is one of the important outcome domains that should be considered when designing chronic pain clinical trials. Although a validated instrument for the assessment of pain-related disability in Iranian chronic low back pain (CLBP) patients exists, to date there is no psychometrically sound instrument to measure pain-related physical disability amongst Iranian chronic pain patients suffering from pain in other parts of their bodies. METHODS Six hundred chronic pain patients completed the Modified version of the Roland-Morris disability questionnaire (M-RMDQ) in addition to questionnaires on demographic variables, pain intensity and depression. RESULTS Internal consistency, test-retest reliability, and concurrent and predictive validity were calculated for the M-RMDQ. Internal consistency of the M-RMDQ items was acceptable (Cronbach's alpha=0.88). Test-retest reliability with a mean 36-day interval between assessments in 76 chronic pain patients was high (ICC=0.90). Concurrent validity was confirmed via significant correlations between the scores of M-RMDQ, depression and pain intensity. Predictive validity of the M-RMDQ was confirmed as it successfully differentiated pain clinic chronic pain patients from the non-pain clinic chronic pain population. CONCLUSION The M-RMDQ has adequate reliability and validity and can be used as a sound measure of physical disability associated with chronic pain among the Iranian population.