Generalized linear model analysis to assess the relationship of the descending pain modulatory system function according to responders (n = 20) and non-responders (n = 13) to the conditioned pain modulation test (CPM-test) on the clinical symptoms and left S1-PAG rs-FC (n = 33)

Outcome: Left S1-PAG rs-FC B SE 95% CI Wald χ2 df P value Effect size
(Intercept) 0.335 0.1816 (–0.021 to 0.690) 3.394 1 0.065
Responders to CPM-test 0.145 0.0457 (0.056 to 0.240) 10.109 1 0.001 0.58
Non-responders to CPM-test reference
Pittsburgh Sleep Quality Index –0.014 0.0058 (–0.026 to –0.003) 6.162 1 0.013 0.45
Fibromyalgia Impact Questionnaire –0.002 0.0010 (–0.004 to 0.001) 4.417 1 0.036 0.38
Pain severity on Numerical Pain Scale (0–10) –0.011 0.0052 (–0.021 to 0.001) 4.395 1 0.036 0.38
Central Sensitization Inventory 0.003 0.0012 (0.001 to 0.005) 5.737 1 0.017 0.44

Primary outcome – generalized linear model analysis to compare responders and non-responders.

The Cramerʼs V was used as a measure of effect size for chi-square tests. The size effect was interpreted as follows: Standards for interpreting Cramerʼs V proposed by Cohen (1988) are the following. DF (degrees of freedom) = 1 (0.10 = small effect) (0.30 = medium effect) (0.50 = large effect). https://www.campbellcollaboration.org/escalc/html/EffectSizeCalculator-R5.php.

P < 0.05 indicates significant differences between treatments in the estimated marginal means adjusted for multiple comparisons by the Bonferroni test.

CPM-test: conditioned pain modulation test, rs-FC: resting-state functional connectivity, S1: primary somatosensory cortex, PAG: periaqueductal gray, B: regression coefficient, SE: standard error, CI: confidence interval, χ2: Wald chi-square, df: degrees of freedom.

Korean J Pain 2023;36:113~127 https://doi.org/10.3344/kjp.22225
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