• Hanna Grundström, Britt Larsson, Lars Arendt-Nielsen, Björn Gerdle, and Preben Kjølhede.
• Department of Obstetrics and Gynaecology in Norrköping, and Department of Biomedical and Clinical Sciences, Linköping University, Norrköping, Linköping, Sweden.
• Scand J Pain. 2020 Jul 28; 20 (3): 635-646.

AbstractBackground and aims Psychological traits such as pain catastrophizing may play a role in the development of chronic pelvic pain (CPP). Pain catastrophizing is the tendency to amplify negative cognitive and emotional pain processes. The Pain Catastrophizing Scale (PCS) assesses elements of pain catastrophizing divided into three subgroups of factors (rumination, helplessness and magnification). Previous studies have shown associations between CPP and increased pain sensitivity, widespread generalized hyperalgesia, and decreased pain thresholds, but the relation between pain catastrophizing and specific pain thresholds has not yet been widely examined in this patient group. The aims of this study were (a) to determine if catastrophizing is increased in women with CPP compared with pain-free women, (b) to assess the importance of pain catastrophizing, psychological distress variables, and subjective pain sensitivity for pain thresholds of heat, cold and pressure in these two groups, and (c) to determine whether psychological variables or pain thresholds best contribute to the differentiation between CPP and controls. Methods Thirty-seven women with chronic pelvic pain who underwent diagnostic laparoscopy on the suspicion of endometriosis participated along with 55 healthy and pain-free controls. All underwent quantitative sensory testing on six locations on the body to determine heat (HPT), cold (CPT) and pressure (PPT) pain thresholds. The PCS, the Pain Sensitivity Questionnaire (PSQ), the Hospital Anxiety Depression Scale, (HADS) demographics and clinical data were collected prospectively. Principal component analysis and orthogonal partial least square regressions were used to assess the associations between PCS scores and pain thresholds. Results The women with CPP scored significantly higher on PCS than the healthy controls. PCS-helplessness, PCS-rumination and HADS-depression were significantly associated with pain thresholds for the whole group. In the CPP group, PCS-rumination, body mass index and PSQ were significant regressors for HPT and CPT. The PCS and the HADS subscales were strongly intercorrelated in women with CPP and were stronger regressors of group membership than the three pain thresholds. In the group of healthy control women, no relationships were found to be significant. The psychological variables were somewhat stronger significant regressors than pain thresholds (also significant) for group membership. Conclusions Women with CPP have significantly higher pain catastrophizing scores than women without CPP. The pain catastrophizing rumination factor is significantly associated with pain thresholds of heat and cold in CPP women. PCS and HADS are strongly intercorrelated and PSQ correlates positively with these variables. It seems that the psychological variables are important for group differentiation. Implications The results clearly indicate the need for a multimodal assessment (bio-psycho-social) of CPP patients including psychological symptoms such as catastrophizing, anxiety and depression. The registration of semi-objective pain thresholds captures both specific pain sensitivity information (mechanical pressure, cold or heat) and the degree of wide spread pain hypersensitivity. There is a need for future larger studies investigating whether certain profiles in the clinical presentations (including pain thresholds and psychological variables) are associated with outcomes after different types of interventions.

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