Background Nociceptive processing in fibromyalgia (FM) patients could be altered by aberrant central mechanisms.
Objectives R-III nociceptive reflex can be used to assess nociceptive processing and to provide indirect evidence of central pain sensitisation.
Methods 95 of 150 FM included in an ongoing RCT of an exercise program vs 40 matched controls (C) were evaluated. Pain severity was assessed by number of tender points (TP), myalgic score (MS) and physician global impression (PGI). Patient’s ratings included a VAS and the regional pain score (RPS). FM and C were assessed by central (R-III) and peripheral (thermotests) quantitative sensory testing (QST). QST and clinical parameters were correlated to CYP2D6 phenotypes.
Results Nearly all FM were female (98%); main reason for exclusion was the inability to interrupt drugs with analgesic properties for >10 days. Age [FM mean 49(SEM1) vs C 46(2) y.], gender and socio-demographic characteristics were similar in both groups. Mean duration of symptoms was 8 y (range 0.4–49). RPS was 64(13–98), VAS was 5.7 (SD 2). Means for clinical examination were: TP 16(0.3), MS 29(0.9) and PGI 2.7(0.1). R-III reflex threshold was reduced in FM [26(2) vs 38(2) mA, p < 0.01]. Thermal perceptions (hot and cold) were similar in both groups, whereas thermal pain thresholds and latency (hot, cold, and cold pressure test) were drastically decreased in FM(p < 0.001). Correlation analysis showed a significant relationship between PGI, and central QST(Pearson r = -0.28; p = 0.02) and between PGI, MS and TP(r = 0.34 and r = 0.66, respectively p < 0.01). Correlation with CYP2D6 activity is under analysis.
Conclusion Physician global impression, but not the other clinical scores, correlates with the extent of central sensitisation. Supported by the SNSF (3200–056028.98).