Reliability of the conditioned pain modulation paradigm to assess endogenous inhibitory pain pathways
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journal contribution
posted on 2018-11-20, 00:00authored byGN Lewis, Luke HealesLuke Heales, DA Rice, K Rome, PJ McNair
BACKGROUND: Conditioned pain modulation paradigms are often
used to assess the diffuse noxious inhibitory control (DNIC) system.
DNICs provide one of the main supraspinal pain inhibitory pathways and
are impaired in several chronic pain populations. Only one previous study
has examined the psychometric properties of the conditioned pain modulation technique and this study did not evaluate intersession reliability.
OBJECTIVES: To evaluate and compare the intra- and intersession reliability of two conditioned pain modulation paradigms using different conditioning stimuli, and to determine the time course of conditioned pain
inhibition following stimulus removal.
METHODS: An electronic pressure transducer was used to determine the
pressure-pain threshold at the knee during painful conditioning of the
opposite hand using the ischemic arm test and the cold pressor test.
Assessments were completed twice on one day and repeated once approximately three days later.
RESULTS: The two conditioning stimuli resulted in a similar increase in
the pressure-pain threshold at the knee, reflecting presumed activation of
the DNIC system. Intrasession intraclass correlation coefficients for the
cold pressor (0.85) and ischemic arm tests (0.75) were excellent. The
intersession intraclass correlation coefficient for the cold pressor test was good (0.66) but was poor for the ischemic arm test (−0.4). Inhibition of the pressure-pain threshold remained significant at 10 min following conditioning, but returned to baseline by 15 min.
CONCLUSIONS: Within-session reliability of DNIC assessment using
conditioned pain modulation paradigms was excellent, but the applicability of assessing pain modulation over multiple sessions was influenced by the conditioning stimulus. The cold pressor test was the superior technique.