Validation of the NARCOMS Registry: pain assessment

The North American Research Committee on Multiple Sclerosis (NARCOMS) Registry is a multiple sclerosis (MS) self-report registry with more than 24 000 participants. Participants report disability status upon enrolment, and semi-annually using Performance Scales (PS), Patient Determined Disease Steps (PDDS) and a pain question. In November 2000 and 2001, we also collected the Pain Effects Scale (PES). Our aim was to validate the NARCOMS pain question using the PES as our criterion measure. We measured correlations between the pain question and age, disease duration, various PS subscales and PDDS to assess construct validity. We correlated pain question responses in participants who reported no change in PDSS or the PS subscales between questionnaires to determine test—retest reliability. We measured responsiveness in participants who reported a substantial change in the sensory, spasticity PS subscales. The correlation between the pain question and PES was r=0.61 in November 2000, and r=0.64 in November 2001 (both P<0.0001). Correlations between the pain question and age, and disease duration were low, indicating divergent validity. Correlations between the pain question and spasticity, sensory PS subscales and PDSS were moderate, indicating convergent validity. Test—retest reliability was r=0.84 (P<0.0001). Responsiveness was 70.7%. The pain question is a valid self-report measure of pain in MS.