Are tender point scores assessed by manual palpation in fibromyalgia reliable? An investigation into the variance of tender point scores.

To determine the reliability of tender point assessment by manual palpation in patients with fibromyalgia, and to investigate the sources of variance, tender point scores by manual palpation were obtained in 30 fibromyalgia patients by 2 investigators; the assessments were repeated after 1 week. Test-retest stability and inter-observer agreement of tender point scores was moderate to high. The most important sources of variance were inter-individual patient differences in (1) mean tenderness (pain thresholds) and (2) tender point profiles (consistent intra-individual differences between the 14 tender point scores), and (3) residual variance, not attributable to any systematic effect (error). It is concluded that the reliability of tender point assessment by manual palpation is acceptable. It seems to be not less than reliability of assessment by pressure algometer. Tender point scores in fibromyalgia reflect individual differences in mean pain thresholds as well as individual tender point profiles.