Reliability of conditioned pain modulation: a systematic review.

Area of Science:

• Pain research
• Neuroscience
• Psychophysics

Background:

• Conditioned pain modulation (CPM) is a key endogenous analgesic mechanism.
• Understanding the reliability of CPM is crucial for its application in clinical and experimental pain research.
• Previous assessments of CPM reliability have yielded varied results, necessitating a systematic review.

Purpose of the Study:

• To systematically review the literature and determine the reliability of conditioned pain modulation (CPM) testing.
• To assess the quality of existing studies on CPM repeatability using the Quality in Prognosis Studies (QUIPS) tool.
• To identify factors influencing the reliability of CPM measurements.

Main Methods:

• Systematic literature review of longitudinal, English-language observational studies on CPM repeatability in adult humans.
• Two independent reviewers assessed risk of bias across 6 domains using the QUIPS tool.
• Interclass correlation coefficients (ICCs) were used to quantify reliability, with defined thresholds for poor, fair, good, and excellent reliability.

Main Results:

• Ten studies were included in the final review; meta-analysis was not feasible due to heterogeneity.
• Intersession reliability of the CPM effect was reported as good (ICC = 0.6-0.75) in 3 studies and excellent (ICC > 0.75) in subgroups of 2 studies.
• Significant risk of bias was noted due to incomplete reporting of demographics, recruitment, attrition, lack of blinding, inadequate control of confounders, and non-standardized statistical analysis.

Conclusions:

• Conditioned pain modulation (CPM) is a reliable measure, but its reliability is highly dependent on stimulation parameters and study methodology.
• Improvements in reporting CPM reliability studies, particularly regarding methodology and bias assessment, are needed.
• Standardized reporting and methodology will facilitate the validation of CPM as a robust prognostic factor in pain research.