Test-retest reliability, repeatability, and sensitivity of an automated deformation-controlled indentation on pressure pain threshold measurement.

The purpose of this study was to construct a computerized deformation-controlled indentation system and compare its test-retest reliability, repeatability, and sensitivity with a manual algometer for pressure pain threshold (PPT) measurements.Pressure pain threshold measurements were made on 16 healthy subjects for 2 sessions on bilateral erector spinae muscles at L1, L3, and L5 spinal levels, consisting of 5 repeated trials each using computerized algometry on one side and manual algometry on the other side. Mean, SD, coefficient of variation, standard error of measurement, minimal detectable change, and intraclass correlation coefficient were calculated for both manual and computerized PPT measurements. Effects of session, level, method, and side on PPT measurements were evaluated using analysis of variance.Manual PPT measurements were significantly larger than computerized PPT measurements (P = .017), and session 2 was significantly larger than session 1 (P = .021). Coefficient of variation, intraclass correlation coefficient, standard error of measurement, and minimal detectable change of the manual and computerized PPT measurements were 10.3%, 0.91, 0.19 kg/cm(2), and 0.54 kg/cm(2) and 15.6%, 0.87, 0.26 kg/cm(2), and 0.73 kg/cm(2), respectively.Although computerized algometry offers the benefits of eliminating the effects of operator reaction time, operator anticipation, alignment error, and variation in indentation rate on PPT measurements, these results indicate that manual algometry using load-controlled strategy may be better than computerized deformation-controlled algometry in terms of test-retest reliability, repeatability, and sensitivity. Constant load-controlled indentation protocol may be more favorable for PPT measurements. Future computerized instrumentation for PPT measurements should adopt a load-controlled mechanism.