Reliability of clinical outcome measures in Charcot-Marie-Tooth disease

We assessed inter- and intra-rater reliability of outcome measures in Charcot-Marie-Tooth disease (CMT) patients. In 40 CMT patients, we assessed reliability of Overall Neuropathy Limitations Scale (ONLS), 10-m timed walk (T10MW), 9-hole-peg test (9-HPT), maximal voluntary isometric contraction (MVIC) of arm (elbow flexion, hand-grip, and three-point pinch) and leg (knee extension, foot dorsiflexion/plantar flexion). Reliability was substantial for ONLS, excellent for T10MW and 9-HPT. For MVIC, inter and intra-rater reliability was excellent for hand contractions; for leg contractions, intra-rater agreement was moderate to substantial, whereas inter-rater agreement was poor.An ad hoc device was produced to immobilize the foot and MVIC reliability was re-assessed in 26 CMT patients, resulting in excellent inter-rater and intra-rater reliability for foot dorsiflexion, and clear inter-rater improvement for foot plantar flexion.All outcome measures appear adequate for CMT assessment. Use of an immobilization device improves foot MVIC reliability, preventing biased findings in patients with greater strength.