Impact of different CRPS phenotypes and diagnostic criteria on quantitative sensory testing outcomes: systematic review and meta-analysis

This review and meta-analysis evaluated the impact of diagnostic criteria and clinical phenotypes on quantitative sensory testing (QST) outcomes in patients with complex regional pain syndrome (CRPS).Eight databases were searched based on a previously published protocol. Forty studies comparing QST outcomes between CRPS-I versus II, warm versus cold CRPS, upper versus lower limb CRPS, males versus females, or using Budapest versus older IASP criteria were included.Studies investigating QST differences between CRPS-I versus II (n = 4), between males versus females (n = 2), and between upper and lower limb CRPS (n = 2) showed no significant differences. Four studies compared QST outcomes in warm versus cold CRPS, showing heat hyperalgesia in warm CRPS, with thermal and mechanical sensory loss in cold CRPS. Although CRPS diagnosed using the Budapest criteria (24 studies) versus 1994 IASP criteria (13 studies) showed similar sensory profiles, there was significant heterogeneity and low quality of evidence in the latter.Based on the findings of this review, classifying CRPS according to presence or absence of nerve lesion into CRPS-I and II, location (upper or lower limb) or according to sex might not be clinically relevant as all appear to have comparable sensory profiles that might suggest similar underlying mechanisms. In contrast, warm versus cold phenotypes exhibited clear differences in their associated QST sensory profiles. To the extent that differences in underlying mechanisms might lead to differential treatment responsiveness, it appears unlikely that CRPS-I vs. II, CRPS location, or patient sex would prove useful in guiding clinical management.