Fibromyalgia antirheumatic drug trials: Effects of a standardized instructional videotape on the reliability of observer-dependent outcome measures

Aims: A study was designed to assess the effects of a standardized instructional videotape on reducing interobserver variability for several commonly used observer-dependent outcome measures. Methods: During a single day, six rheumatologists independently examined six patients with fibromyalgia (FM) in a predetermined order using a Latin square design, before and after viewing a standardized videotape which demonstrated methods for performing dolorimetry and for detecting skinfold tenderness and reactive hyperaemia. Reliability coefficients were calculated based on the variance components of the analysis of variance (ANOVA) table. Results: Prestandardization reliability coefficients were <0.80 for 8 measures. Following standardization all reliability coefficients approximated to or exceeded 0.80. Conclusions: An important and beneficial effect of the standardization procedure was noted for several outcome variables. Such reductions in observer variability have the potential to diminish sample size requirements for FM antirheumatic drug studies. The use of a videotape to achieve this goal has obvious cost and convenience advantages over one-on- one training procedures.