The multiple sclerosis functional composite: different practice effects in the three test components.

Background: The multiple sclerosis functional composite (MSFC) is a multidimensional, MS-specific outcome measure for use in clinical trials, comprising three tests: timed 25-foot walk (T25FW), paced auditory serial addition (PASAT), and 9-hole peg (9HP).

Objective: To assess interrater and intrarater reliability and practice/fatigue effects in the MSFC.

Methods: The MSFC was administered by two neurologists after a formal training session to 32 MS outpatients. Patients were assessed four times by one examiner and twice by the other. The six tests were administered in a single day, with at least 20 min of rest between them. The examiners were blinded to the results of previous assessments. Testing order was random.

Results: Interrater reliability was excellent, with intraclass correlation coefficients (ICC) ranging from 0.93 for 9HP (95% confidence interval [CI] 0.84-0.96) to 0.99 for T25FW (95% CI 0.97-0.99). For intrarater reliability, ICC ranged from 0.93 for PASAT (95% CI 0.82-0.97) to 0.98 for T25FW (95% CI 0.93-1.00). We found no practice effect for T25FW after the first administration. However, performance improved with testing over the first three sessions for PASAT and over the first four sessions for 9HP.

Conclusions: The MSFC is characterised by excellent reliability. Practice effects for the three MSFC components differed, being negligible for T25FW and evident for PASAT and 9HP. To improve efficiency, we suggest one prebaseline administration of T25FW, three of PASAT and four of 9HP.