Patient-reported questionnaires and quantitative sensory testing for central sensitization in endometriosis

Endometriosis is a chronic inflammatory condition affecting over 2 million Canadians. It is characterised by the growth of endometrial-like lesions outside the uterus, causing debilitating pain. Standard treatments include pain medication, hormonal therapy and surgery; yet 30-50% still experience pain. Endometriosis pain includes nociceptive, neuropathic, and nociplastic types. Nociplastic pain is characterized by central nervous system sensitization, which leads to hyperalgesia and allodynia, and provides an explanation for persistent and widespread pain. In Objective 1, I conducted a scoping review to identify tools for detecting nociplastic pain and central sensitization in endometriosis. This review listed potential clinical and research tools, including sensory tests and patient-reported questionnaires as useful proxies for central sensitization but highlighted gaps in research evaluating the efficacy of these tools. Objective 2 involved a retrospective analysis of the Endometriosis and Pelvic Pain Interdisciplinary Cohort registry (EPPIC) which looked at the association between the Pain Sensitivity Questionnaire (PSQ) with the Central Sensitization Inventory (CSI), central sensitivity syndromes, and patient-reported pain and quality of life. The PSQ was weakly correlated with the CSI (r=0.099, p<0.001) and showed weaker correlations with the central sensitivity syndromes (r=0.093, p<0.001) compared to the CSI (r=0.687, p<0.05). The PSQ was only associated with superficial dyspareunia (r=0.138, p<0.001) and back pain (r=0.091, p=0.014), whereas the CSI was significantly associated (i.e. p<0.05) with scores for dysmenorrhea, deep dyspareunia, superficial dyspareunia, back pain and chronic pelvic pain. In Objective 3, an interim analysis of an ongoing prospective study examined five pain questionnaires and six sensory tests across the hand, abdomen, and deltoid. Findings indicated a significant (i.e. p<0.05) strong relationship between the Self-Administered Leeds Assessment for Neuropathic and Nociceptive Signs and Symptoms (S-LANSS) with all questionnaires, except the PSQ: Douleur Neuropathique 4 Questionnaire (DN4; r=0.64), Michigan body map (MBM; r=0.58), and CSI (r=0.52). Additionally, pelvic mechanical hypersensitivity was linked to more widespread pain (r=0.75) and neuropathic-like symptoms (r=0.59). However, patient-reported symptoms were more strongly associated with the CSI and S-LANSS than sensory tests. Overall, endometriosis nociplastic pain is heterogeneous, and may require multiple assessment methods. Larger studies are needed to confirm these findings.