Control and "fibrositic" tenderness: comparison of two dolorimeters.

It can be as important to quantify lack of tenderness, as tenderness. Palpation detects tenderness only; dolorimeters with a limited scale restrict ability to assess variations in thresholds at clinically nontender sites. Such variations must be measured if we are to evaluate generally acting factors affecting tenderness. We measured thresholds at "fibrositic" and control sites in 8 subjects, using 2 observers and 2 different dolorimeters. The traditional Chatillon dolorimeter yielded twice as many readings off the 9 kg scale (17 of 96 versus 8 of 96) as the Fischer instrument, with a scale of 11 kg [continuity corrected (chi 2 = 3.725, p = 0.086)/bd. The Fischer instrument also used a footplate with a smaller diameter, and results using the 2 instruments were not parallel. Median values were the same (5.1 kg), but the Fischer instrument gave lower readings at tender sites (10th percentile 2.4 versus 2.9 kg) and higher values at nontender sites. Thresholds at fibrositic and control sites were significantly correlated, reinforcing evidence of generally acting factors affecting tenderness.