Objective: To evaluate interrater reliability using 5 newly trained observers in the assessment of pressure pain threshold (PPT) using a fixed-angle algometer. Methods: The study design comprised 2 phases. Phase 1: 5 undergraduate physical therapists were trained in algometry at a predefined angle, at a rate of 5 Newtons (N)/s, to the first dorsal interosseous muscle. Each observer then underwent a competency test of the application speed. The aim was to achieve repeated applications at 5 N/s without visual feedback from the algometer. Phase 2: the 5 observers measured PPT of 13 healthy volunteers, at the first dorsal interosseous muscle. The sequence of observer measurements for each participant was randomized. Mean PPT values for each observer were analyzed using repeated measures analysis of variance, intraclass correlation coefficient (ICC2,1), and standard error of measurement, with 95% confidence intervals (CIs). Results: No significant differences between observers’ mean values were found (P = 0.094), suggesting no bias. The ICC was 0.91 (95% CI 0.82, 0.97). The standard error of measurement value was 6.27 N/cm 2 (95% CI 5.35, 7.59). Differences in PPT measurements of more than 17.39 N/cm 2 (1.77 kg/cm 2 ) are likely to exceed the magnitude of measurement error, and could be used to indicate true change. This margin of error is, however, somewhat larger than a previously proposed minimum clinically important difference in PPT of 14.71 N/cm 2 (1.5 kg/cm 2 ). Discussion: This study provides new evidence that trained observers can apply an algometer at a consistent rate and provide highly reliable measures of PPT in healthy humans, when PPT is calculated as the mean of 3 trials.

Interrater reliability of algometry in measuring pressure pain thresholds in healthy humans, using multiple raters

Background and Purpose. Algometers have been used to measure muscle and other soft tissue tenderness. The purpose of this study was to investigate (1) “normal” pressure-pain threshold (PPT) in the biceps brachii muscle, (2) the reliability of repeated measurements of PPT in subjects without pain over 3 consecutive days, (3) the reliability of measurements of PPT between examiners, and (4) the number of measurements required to obtain a best estimate of PPT. Subjects. Thirty-five subjects participated in the study. Methods. Pain-pressure threshold of the biceps brachii muscle was measured using a Fischer algometer. Three test trials were done on each subject on each of 3 days by each of two examiners. Intraclass correlation coefficients (ICCs) and graphical methods were used to analyze the results. Results. The ICCs revealed almost perfect reliability for measurements of PPT within and across 3 days and substantial reliability between examiners. The best estimate of PPT was obtained using the mean of the second and third trials each day. Graphical methods demonstrated that agreement between examiners was greatest at low mean pain thresholds. There was no effect for order of examiner. Conclusion and Discussion. The PPT is a reliable measure, and repeated algometry does not change pain threshold in healthy muscle over 3 consecutive days. The PPT can be used to evaluate the development and decline of experimentally induced muscle tenderness. Reliability is enhanced when all measurements are taken by one examiner.

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Reliability of Clinical Pressure-Pain Algometric Measurements Obtained on Consecutive Days

https://www.archives-pmr.org/article/S0003-9993(02)00060-6/pdf

Immediate effects of various physical therapeutic modalities on cervical myofascial pain and trigger-point sensitivity

Quantitative sensory testing (QST) is an instrument to assess positive and negative sensory signs, helping to identify mechanisms underlying pathologic pain conditions. In this study, we evaluated the test-retest reliability (TR-R) and the interobserver reliability (IO-R) of QST in patients with sensory disturbances of different etiologies. In 4 centres, 60 patients (37 male and 23 female, 56.4±1.9years) with lesions or diseases of the somatosensory system were included. QST comprised 13 parameters including detection and pain thresholds for thermal and mechanical stimuli. QST was performed in the clinically most affected test area and a less or unaffected control area in a morning and an afternoon session on 2 consecutive days by examiner pairs (4 QSTs/patient). For both, TR-R and IO-R, there were high correlations (r=0.80-0.93) at the affected test area, except for wind-up ratio (TR-R: r=0.67; IO-R: r=0.56) and paradoxical heat sensations (TR-R: r=0.35; IO-R: r=0.44). Mean IO-R (r=0.83, 31% unexplained variance) was slightly lower than TR-R (r=0.86, 26% unexplained variance, P<.05); the difference in variance amounted to 5%. There were no differences between study centres. In a subgroup with an unaffected control area (n=43), reliabilities were significantly better in the test area (TR-R: r=0.86; IO-R: r=0.83) than in the control area (TR-R: r=0.79; IO-R: r=0.71, each P<.01), suggesting that disease-related systematic variance enhances reliability of QST. We conclude that standardized QST performed by trained examiners is a valuable diagnostic instrument with good test-retest and interobserver reliability within 2days. With standardized training, observer bias is much lower than random variance. Quantitative sensory testing performed by trained examiners is a valuable diagnostic instrument with good interobserver and test-retest reliability for use in patients with sensory disturbances of different etiologies to help identify mechanisms of neuropathic and non-neuropathic pain.

Test-retest and interobserver reliability of quantitative sensory testing according to the protocol of the German Research Network on Neuropathic Pain (DFNS): a multi-centre study.

https://research.vu.nl/ws/files/2892390/263592.pdf

Interobserver reproducibility of the assessment of severity of complaints, grip strength, and pressure pain threshold in patients with lateral epicondylitis

This study was designed to establish the intra-rater and inter-rater reliability of measurements of trigger point sensitivity using a commercially available pressure threshold meter. Fifty healthy adult volunteers (25 men and 25 women, aged 20 to 51 years) underwent repeated pressure threshold readings from two separate trigger point locations in the trapezius muscle, TP2 (left) and TP3 (right) by two independent examiners. Pressure threshold readings, using a 1.0 kg/s application, were done alternately by each experimenter. Measurements from each trigger point were completed 5 minutes apart. Intraclass correlation coefficients (ICC) revealed the inter-rater reliability to be high for both the first (ICC = 0.82) and second trial (ICC = 0.90) of TP2 and for the first (ICC = 0.86) and second trial (ICC = 0.92) of TP3. Intra-rater reliabilities for TP3 (ICC = 0.91) were higher than for TP2 (ICC1 = 0.80; (ICC2 = 0.83). These results show that the pressure threshold meter is highly reliable in measuring trigger point sensitivity, between and within experimenters, and may be useful in the diagnosis and monitoring of treatment of myofascial pain syndrome.

G A Delaney

Papers

Inter- and intra-rater reliability of the pressure threshold meter in measurement of myofascial trigger point sensitivity