PRESSURE PAIN THRESHOLD AND CONDITIONED PAIN MODULATION IN ASYMPTOMATIC AND SYMPTOMATIC PARTICIPANTS WITH CHRONIC SHOULDER PAIN: A RELIABILITY STUDY

P. Kalamatas-Mavrikas¹, N. Vasilis^1,2, P. Bilika¹, E. Kapreli¹

¹Clinical Exercise Physiology and Rehabilitation Research Laboratory, School of Health Sciences, University of Thessaly, Physiotherapy, Lamia, Greece, ²Performance 22 Lab, Attika, Greece

Background: A subgroup of patients with chronic shoulder pain (approximately 15-20%) present increased sensitivity in mechanical stimuli and symptoms related to central sensitization. Pressure Pain Threshold (PPT) and Conditioned Pain Modulation (CPM) are two quantitative sensory tests (QST) that provide information about hyperalgesia, allodynia, and pain modulation. The presence of hyperalgesia and altered pain modulation can predict disability and psychological distress. Although PPT and CPM were used to inform about the mechanism of pain, there are few studies with low methodological quality which assess the reliability of PPT and CPM.

Purpose: The purpose of this study was to assess the intra-rater and inter-rater reliability of PPT and CPM testing in patients with shoulder pain and healthy participants.

Methods: A total of fifty-one participants (18-65 years) were recruited. Two independent raters assessed PPTs and performed CPM testing with a time interval of 1 day between the sessions. A digital algometer was used for the PPTs. The subjects pushed a button when the pressure had started to be painful. The measurement sites were located at the affected or dominant upper limb in the upper trapezius, middle deltoid, and the opposite side in the tibialis anterior muscle. During the CPM test, the participants put their hand in a metal bowl with water (approximately 4^oC) for 20 sec (twice). Then the PPT in the upper trapezius was assessed again. The temperature, lighting and humidity of the room were constant during the measurements.

Results: According to our results, the intra-rater reliability (ICC=0.949-0.989) and inter-rater reliability (ICC=0.842-0.945) were excellent to good for PPT (N=51). The SEM ranged between 24.23 and 38.27 in the measurements by the same rater and 62.58-102.25 between the raters. The SDC was 19.27-36.35 and 53.59-75.07 respectively. The intra-rater reliability was moderate (ICC=0.72) and inter-rater reliability was poor (ICC=0.267) for the CPM test (N=51). The SEM for CPM test was 11.65 in the repeated measurements by the same rater and 22.18 between the raters. The SDC was 27.95 and 53.31 respectively. The subgroup analysis revealed that the inter-rater reliability for CPM was extremely low.

Conclusions: PPT proved to be a reliable test in the included population both in repeated trials of the same rater and among raters in healthy participants and patients with shoulder pain. Although the CPM test seems to provide reliable results when used by the same examiner, when used by different examiners it seems to present lower values of reliability, especially in the symptomatic group.

Implications: Clinical therapists should be aware and careful in the use of PPT and CPM taking under consideration the SEM and SDD values when clinically significant differences are important (such as when examining an intervention effect on patient’s symptoms). CPM is a very sensitive test and cognitive factors may affect its results. Clinical decisions should not base only on PPT and CPM.

Funding acknowledgements: Paraskevi Bilika was funded by the Center of Research Innovation and Excellence of the University of Thessaly.

Keywords:
Quantitative Sensory Testing
Shoulder pain
Psychometric properties

Topics:
Musculoskeletal: upper limb
Pain & pain management
Research methodology, knowledge translation & implementation science

Did this work require ethics approval? Yes

Institution: University of Thessaly

Committee: Committee for Research Ethics of Department of Physiotherapy

Ethics number: 710/23-09-2021