Background & Aims

The reproducability of Pressure Pain Thresholds (PPT) is high, even among novice raters, although notable variability in measurement error exists among raters, indicating varying levels of precision. Discrepancies in training durations may underlie this variability, given the psychomotoric nature of PPT measurement. Achieving minimal measurement error is crucial for enhancing precision in detecting changes in pain sensitivity, both in clinical settings and research, and when PPT is used as test stimulus in dynamic pain measurements (e.g., Conditioned Pain Modulation). Consequently, identifying factors influencing reproducibility, including rater and participant experience, holds promise for refining PPT measurements.

This study aimed to assess 1) the impact of rater experience on measurement error in PPT assessments, and 2) the influence of potential factors stemming from rater and participant characteristics (including participant experience) on measurement error.

Methods

Two distinct longitudinal experiments were conducted, one focusing on the tibialis anterior in the leg and the other on the extensor carpi radialis in the arm. Each experiment involved a (new) group of 6 unexperienced raters (3 physiotherapy students, 3 physiotherapists) and a (new) group of 72 unexperienced participants. The raters recieved general instructions, a single demonstration and feedback on a single practise measurement. They further received feedback after each block of 12 participants. In 6 blocks of 12 participants, 72 participants were measured using a digital algometer (FPX25, Wagner) in 3 days per experiment. For agreement, ANOVA was used for the standard error of measurement (SEM) per rater, and total group, per block. Then, differences between test-retest measurements were analysed with Linear Mixed Models (LMM), clustered on rater and participant, with rater and participant experience and rater characteristics including strength and dexterity as fixed effects.

Results

In both experiments, the initial SEM was low, even without prior training, and further decreased with increased experience. In the leg experiment, SEM decreased from 5.7 (95% CI 5.0 – 6.6) to 4.2 (95% CI 3.6 – 4.9) kg/cm². Similarly, in the arm experiment, SEM decreased from 3.5 (95% CI 3.0 – 4.0) to 2.4 (95% CI 2.1 – 2.8) kg/cm². The LMM analysis indicated significant effects of rater experience (? = -0.2, p = .035), rater being a physiotherapy student (? = -0.64, p = .02), rater strength (? = 0.01, p < .001), and participant experience (? = -0.24, p = .002).

Conclusions

Inexperienced raters demonstrate reproducible PTT measurements even without training, with enhanced reproducibility observed as they gain experience. Various rater factors impact measurement error, alongside participant-related factors. Notably, student raters exhibit more reliable measurements, validating participation in research projects during their study. Moreover, participant experience significantly influences measurement reproducibility, underscoring the importance of providing familiarization before PPT testing in both clinical and research settings.

References

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Presenting Author

Roland Reezigt

Poster Authors

Roland Reezigt, MSc

MSc

Hanze University of Applied Sciences

Lead Author

E-mail

Topics

  • Assessment and Diagnosis