Clinical pressure pain threshold testing in neck pain

Quantitative sensory testing, including pressure pain threshold (PPT), is being used more frequently in clinical practice. In order to facilitate clinical utility, knowledge of the properties of the tool and interpretation of results are necessary. This observational study used a clinical sample of people with mechanical neck pain to determine the influence of number of testing repetitions on measurement properties, reliability and minimum clinically important difference, and associations between PPT and key psychological constructs. The total sample was 206 participants, though not all participants provided data for all analyses. Interrater and 1-week test-retest reliability were excellent (intraclass correlation coefficients [2,1]=.75-.95). Potentially important differences in reliability and PPT scores were seen when using only 1 or 2 repeated measures compared with all 3. The PPT over a distal location (tibialis anterior muscle) was not sufficiently responsive in this sample, but the local site (upper trapezius muscle) was responsive and may be useful as part of a protocol to evaluate clinical change. Sensitivity values (range=0.08-0.50) and specificity values (range=0.82-0.97) for a range of change scores are presented. Depression, catastrophizing, and kinesiophobia were able to explain small but statistically significant variance in local PPT (3.9%-5.9%), but only catastrophizing and kinesiophobia explained significant variance in the distal PPT (3.6% and 2.9%, respectively).

The results indicate that PPT is sufficiently reliable and that 3 measurements should be taken to optimize measurement properties. The variance explained by the psychological variables was small but significant for 3 constructs related to catastrophizing, depression, and fear of movement. Clinical implications for application and interpretation of PPT are discussed.