74 Pain Modulatory Phenotypes Differentiate Chronic Pancreatitis Patients With Distinct Clinical Pain Profiles

Abstract

INTRODUCTION: Pain is a common problem in patients with chronic pancreatitis (CP) and effective therapy remains a considerable challenge. Methods based on quantitative sensory testing (QST) provide information on pain modulation and have demonstrated promise in predicting future pain status and the efficacy of analgesics. The aims of this study were to evaluate the existence of CP subgroups with different pain modulatory phenotypes and to investigate associations with patients' clinical pain and psychological profiles. METHODS: This was a cross-sectional, multicentre study of CP outpatients. Patients fulfilled a number of questionaries' including the Brief Pain Inventory short form, the Hospital Anxiety and Depression Score as well as measures of Conditional and Situational Pain Catastrophising. Using a standardized QST protocol, we recorded pain detection thresholds (PDTs) to static muscle pressure stimulations at the “pancreatic dermatomes” on the upper abdomen and back and at three control areas. The ratio between pancreatic and control PDTs were calculated (PDT-index) to offset interindividual differences in absolute thresholds. The PDT-index was used in conjunction with repetitive pinprick stimulations (temporal summation) applied at the abdominal pancreatic dermatome to obtain a measure of segmental hyperalgesia. A conditioned pain modulation (CPM) paradigm was performed to investigate descending pain modulation. Patients were grouped based on normative QST reference values and questionnaire scores were compared across subgroups to investigate associations between patients' pain modulatory phenotypes and clinical pain and psychological profiles. RESULTS: A total of 91 patients were enrolled in the study. The mean age was 53.1 ± 12.7 y, 62% were men, and 65% had toxic etiology. Three distinct pain modulatory phenotypes were found: group 1 (n = 31) had normal pain modulation; group 2 (n = 17) had segmental sensitization; group 3 (n = 43) had widespread sensitization. Patients with widespread sensitization had higher pain score (P < 0.01) and lower QOL (P < 0.05) in comparison to segmental and normal. In contrast, psychological features were comparable across subgroups. CONCLUSION: CP patients with widespread sensitization have significantly higher levels of pain and lower QOL. QST characterizes the sensory profiles independently of the patient's psychological status and provides an unbiased proxy of pain processing. This information can be used for prognostication and tailoring of management strategies.