Pos1346 chasing pain: exploring somatosensory profiles in patients with rheumatological diseases through quantitative sensory testing

Background Pain reflects a major symptom in many rheumatological diseases. To assess nociceptive and non-nociceptive submodalities of different afferent nerve fiber groups and central pathways, and to examine the presence of sensitive plus or minus signs such as hyperalgesia or hypesthesia, the “Quantitative Sensory Testing” (QST) approach was developed. QST, established by the German Neuropathic Pain Research Network (DFNS), is meant to be used for the generation of somatosensory profiles [1]. These can then be used as a guidance to improve a targeted pain medication. Objectives The goal of this study is to explore whether patients with rheumatoid arthritis (RA), psoriatic arthritis (PsA), axial spondyloarthritis (axSpA) and systemic sclerosis (SSc) show differences in somatosensory profiles between each other and in contrast to a healthy control group. Methods In this monocentric five-armed study (ethical approval under Institutional Review Board #065/20), four groups of each 20 patients with RA, PsA, axSpA or SSc, and one control group consisting of 20 healthy individuals were collected and a somatosensory profile using the standardized procedure of QST was created for each one of the 100 participants. QST included both small fiber mediated stimuli and large fiber mediated stimuli, via all categories shown in Figure 1. The vibration detection threshold where the detection of vibration is ranked on a scale from zero to eight, with ‘8’ being normal perception of vibration, serves as an example for large fiber mediated stimuli. Additionally, standard questionnaires incorporating laboratory parameters, joint manifestations and pain condition were used to determine disease activities (BASDAI, PASDAS, CDAI and mRSS). Results A preliminary data analysis of all 100 study participants found occurrence of allodynia in 5% of patients with SSc, 15% of RA, 25% of PsA, and 15% of all axSpA patients, compared with 0% in the control group. Considering the vibration detection threshold, there was little difference between all disease groups, also in comparison to the control group: SSc (mean ± SD: 7,79 ± 0,34), RA (mean ± SD: 7, 66± 0,4), PsA (mean ± SD: 7,76 ± 0,34), AxSpA (mean ± SD: 7,69 ± 0,57) and control group (mean ± SD: 7,98 ± 0,16). Conclusion The analysis for allodynia occurrence indicates the presence of sensory gain towards small fiber mediated stimuli in all four disease groups studied. Until now, our vibration detection threshold studies do not suggest a loss or gain of sensory function for large fiber mediated stimuli. The full analysis completion is expected in March 2023. Reference [1]R.Rolke et al. Quantitative sensory testing: a comprehensive protocol for clinical trials, European Journal of Pain 10,2006; p. 77-88 Figure: Small fiber mediated stimuli Large fiber mediated stimuli CDT 1 A δ-Fibers VDT 12 Aβ-Fibers WDT 2 C-Fibers MDT 13 Aβ-Fibers TSL 3 , PHS 4 A δ -Fibers, C-Fibers ALL 11 Aβ-Fibers CPT 5 , HPT 6 A δ -Fibers, C-Fibers MPT 7 A δ -Fibers, C-Fibers MPS 8 A δ -Fibers, C-Fibers WUR 9 A δ -Fibers, C-Fibers PPT 10 A δ -Fibers, C-Fibers ALL 11 A δ -Fibers, C-Fibers QST-Testing categories with their associated nerve fibers (1) Cold detection threshold, (2) Warm detection threshold, (3) Thermal sensory limen, (4) Paradoxical heat sensations, (5) Cold pain threshold, (6) Heat pain threshold, (7) Mechanical pain threshold, (8) Mechanical pain sensitivity, (9) Wind-up-Ratio, (10) Pain pressure threshold, (11) Allodynia, (12) Vibration detection threshold, (13) Mechanical detection threshold. Acknowledgements: NIL. Disclosure of Interests None Declared.