Reproducibility of tender point examination in chronic low back pain patients as measured by intrarater and inter-rater reliability and agreement: a validation study

OBJECTIVES: To evaluate the reliability and agreement of digital tender point (TP) examination in chronic low back pain (LBP) patients. DESIGN: Cross-sectional study. SETTINGS: Hospital-based validation study. PARTICIPANTS: Among sick-listed LBP patients referred from general practitioners for low back examination and return-to-work intervention, 43 and 39 patients, respectively (18 women, 46%) entered and completed the study. MAIN OUTCOME MEASURES: The reliability was estimated by the intraclass correlation coefficient (ICC), and agreement was calculated for up to ±3 TPs. Furthermore, the smallest detectable difference was calculated. RESULTS: TP examination was performed twice by two consultants in rheumatology and rehabilitation at 20 min intervals and repeated 1 week later. Intrarater reliability in the more and less experienced rater was ICC 0.84 (95% CI 0.69 to 0.98) and 0.72 (95% CI 0.49 to 0.95), respectively. The figures for inter-rater reliability were intermediate between these figures. In more than 70% of the cases, the raters agreed within ±3 TPs in both men and women and between test days. The smallest detectable difference between raters was 5, and for the more and less experienced rater it was 4 and 6 TPs, respectively. CONCLUSIONS: The reliability of digital TP examination ranged from acceptable to excellent, and agreement was good in both men and women. The smallest detectable differences varied from 4 to 6 TPs. Thus, TP examination in our hands was a reliable but not precise instrument. Digital TP examination may be useful in daily clinical practice, but regular use and training sessions are required to secure quality of testing.