Improving QST Reliability--More Raters, Tests, or Occasions? A Multivariate Generalizability Study

The reliability of quantitative sensory testing (QST) is affected by the error attributable to both test occasion and rater (examiner) and the interactions between them. Most reliability studies account for only 1 source of error. The present study employed a fully crossed, multivariate generalizability design to account for rater and occasion variance simultaneously. Nineteen healthy volunteers were examined with a battery of 7 QST procedures 4 times on 2 occasions by 2 raters. The QST battery was composed to include a mix of different pain stimuli and response domains, including threshold, intensity, tolerance, and modulation with mechanical, thermal, and chemical stimuli. The classical test-retest and interrater reliability (.19 < intraclass correlation coefficient <.92) was in line with the literature, and generalizability analysis indicated that the universe score was generally the dominant source of variation (relative contribution = 19%, 78%). Error attributable to the interaction between study participant and occasion was also influential. Dependability coefficients indicated that a substantial increase in reliability and feasibility could be achieved by employing a composite QST battery compared to single QST procedures. Reliability was improved more by repeated testing on separate occasions than by repeated testing by different raters.

When balancing reliability and feasibility, the current findings suggest that a carefully selected battery of QST procedures repeated on a few occasions may be optimal.