In an ALS clinic population, the total Amyotrophic Lateral Sclerosis Functional Rating Scale-revised score at baseline is a strong predictor of death or tracheostomy independently of forced vital capacity and after adjustment for age at baseline, sex, and symptom duration.

We wished to determine whether the Amyotrophic Lateral Sclerosis Functional Rating Scale-revised (ALSFRS-R) is reliable when used as primary outcome measure in a multicenter clinical trial. To establish inter-rater reliability, we randomly assigned 19 primary raters and 11 back-up raters to score nine amyotrophic lateral sclerosis (ALS) patients using the ALSFRS-R. To assess intra-rater reliability and reliability of telephone administration, we randomly assigned consecutive participants of the Clinical Trial of High Dose Coenzyme Q10 in ALS (QALS) to have in-person ALSFRS-R interviews at both screening and baseline visits (n=41 patients) or to have the ALSFRS-R interview by telephone at screening and in person at the baseline visit (n=27). An intraclass correlation coefficient (ICC) of reliability was calculated using a one-way random effects analysis of variance model. In the inter-rater reliability assessment, the primary raters performed 54 ratings on nine patients with ICC=0.93 (95% CI 0.84-0.98). For back-up raters, 32 ratings on nine patients resulted in ICC=0.93 (95% CI 0.82-0.98). The intra-rater reliability for in-person interviews was ICC = 0.95 (95% CI 0.92-0.98). The reliability of telephone administration compared to in-person interviews was ICC=0.97 (95% CI 0.93-0.98). We conclude that the ALSFRS-R shows excellent inter- and intra-rater reliability, and reliability of telephone administration when used as primary outcome measure in a multicenter ALS trial.