RELIABILITY OF PRESSURE PAIN THRESHOLD AND CONDITIONED PAIN MODULATION IN HEALTHY PARTICIPANTS AND PATIENTS WITH CHRONIC LOW BACK PAIN

N. Vasilis^1,2, P. Kalamatas-Mavrikas¹, 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: Pressure Pain Threshold is a non-invasive test that measured the static mechanical threshold of pain. Conditioned Pain Modulation is an experimental measure of the endogenous pain inhibitory pathway. Both measures are used in clinical practice to provide information on the type of pain based on neurophysiological mechanisms. Several studies have reported that there is increased mechanical sensitivity and alteration of the pain inhibition function in patients with chronic low back pain. Nevertheless, only a few pieces of evidence confirm the reliability of PPT in chronic low back pain, while there is a great lack of studies on the reliability of CPM.

Purpose: This study aimed to examine the absolute and relative reliability (intra and inter-rater) in patients with Low Back Pain (LBP) and healthy participants.

Methods: Thirty-one healthy participants and twenty-one patients with chronic (>3 months) low back pain were included. The participants completed two tests in random order. In the PPT test, they were asked to press a switch when the gradually increasing pressure, applied by the examiner to the skin of the examinee, begins to become unpleasant. The sites selected had also been used in previous studies. For CPM after measuring the pain threshold at a point in the upper trapezoid, participants placed their wrist in a basin with cold water (4°C). Then the threshold of pain was measured again at the same point. The temperature, lighting, and humidity of the room were kept constant during the examinations. The subjects were assessed by two independent raters in two sessions with an interval of 24 hours. The Central Sensitization Inventory, the Hospital Anxiety, and Depression, and International Physical Activity Questionnaire were also completed by the participants.

Results: Excellent intra-rater (ICC=0.928-0.98) and inter-rater (ICC=0.91-0.98) reliability were observed in all sites for PPT (Ν=52). The SDC was estimated at 23.19-40.75 (same rater) and 26.61-74.47 (different raters). The SEM was 19.36 -72.12 (same rater) and 28.26-119.91 (different raters). Good intra-reliability was found for CPM (ICC=0.80) but inter-rater reliability was poor (ICC=0.464). The SEM was calculated at 12.32 and SDC 29.66 (same rater) and 19.53 and 46.21 (different raters) approximately. The subgroup analysis for PPT (patients and control group) yielded the healthy group presents excellent intra-rater (ICC=0.935-0.981) and inter-rater (ICC=0.943-0.992) reliability. Intra-rater (ICC=0.768- 0.987) and inter-rater (0.812-0.988) reliability in patients’ group were good to excellent. Moderate intra-rater (ICC=0.669) and poor inter-rater (ICC=0.365) reliability was found for CPM in control group while good intra-rater (ICC=0.896) and moderate (ICC=0.563) was found in patients’ group.

Conclusions: PPT and CPM are reliable measures when procedures are organized and standardized, however, clinical therapists should be conscious when evaluations are carried out by different therapists.

Implications: CPM can give important information about the functioning of the endogenous pain inhibitory systems, further studies exploring the clinical inter-reliability of CPM are needed to strengthen the results of the current study.

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

Keywords:
Quantitative Sensory Testing
Low Back Pain
Reliability

Topics:
Pain & pain management
Musculoskeletal: spine

Did this work require ethics approval? Yes

Institution: University of Thessaly

Committee: Committee for Research Ethics of Department of Physiotherapy

Ethics number: 711/23-09-2021