Pancreatic QST Differentiates Chronic Pancreatitis Patients into Distinct Pain Phenotypes Independent of Psychiatric Comorbidities

Abstract

Background & aims: Quantitative sensory testing (QST) has been previously used to study pain in chronic pancreatitis (CP) but included methods that are not suitable for clinical purposes. The aims of this study were to determine if pancreatic QST (P-QST) can differentiate patients into distinct pain phenotypes and to determine the association of these with their clinical pain and psychiatric comorbidities.

Methods: A multicenter cross-sectional study was conducted where patients completed validated questionnaires assessing quality of life (QoL), depression and anxiety scores as well as clinical pain symptoms followed by P-QST which included a cold pressor test, repetitive pinprick stimuli and pressure stimulation of the upper abdominal (T10) and control dermatomes. P-QST categorized patients into pain phenotypes based on a previously established nomogram. QoL, clinical pain and psychiatric assessment scores were compared across these groups.

Results: A total of 179 patients were enrolled with a mean age of 54.1±13.6 years among whom 59% were males and 42% had an alcoholic etiology. P-QST showed no hyperalgesia in 91 (51%), segmental hyperalgesia in 50 (28%) and widespread hyperalgesia in 38 (21%) patients. Patients with widespread hyperalgesia had significantly higher pain intensity scores (P = .03) and rates of constant pain (P = .002) as well as decreased QoL (P < .001) and physical functioning (P =.03) in comparison with the other two pain phenotypes. In contrast, psychiatric comorbidities were similar across all groups.

Conclusions: P-QST may serve as a novel unbiased pain assessment tool in CP as it categorizes patients into distinct pain phenotypes independent of their psychiatric comorbidities.

Keywords: Abdominal Pain; Central Sensitization; Hyperalgesia; Quality of Life.

Copyright © 2022 AGA Institute. Published by Elsevier Inc. All rights reserved.

Figures

Figure 1.

Illustration of the method used for assessment of the pain system. Due to convergence between afferents from the pancreas and those of the skin in the T10 dermatome (upper abdomen and back), increased afferent barrage from the pancreas may result in central sensitization at this level. This will result in a segmental lowering of the pain threshold to pancreatic quantitative sensory testing (P-QST) of the skin and deep tissue (P-QST site 1). If the sensitization spreads along the neuroaxis there will also be a lowering of pain thresholds in other areas such as L4 (P-QST site 2). The efficacy of bulbospinal descending pathways that can gate the afferent barrage, and this inhibit pain pathways are also tested indirectly. Pain is, however, not only a result of nociceptive processing but also activates other brain centers dealing with affective, cognitive and evaluative processing involved in the complex sensory process. During pain chronification such components of pain may dominate the clinical picture.

Figure 2

a. Distribution of P-QST phenotypes among patients with painful, no current pain and painless CP. b. Distribution of clinical pain patterns by P-QST phenotypes. Patients with evidence of central sensitization (segmental or widespread hyperalgesia) were characterized by higher proportions of patients with constant pain, as opposed to intermittent or no current pain, compared to patients with no hyperalgesia by P-QST (P = .002)

Figure 3

a. Distributions of BPI pain scores and BPI interference scores by P-QST phenotypes. The BPI pain scores (P =.03) and BPI interference scores (P = .02) were highest in the subgroup of patients with widespread hyperalgesia and lowest in the subgroup with no hyperalgesia. b. Radar chart demonstrating QoL and the five functional scales of EORTC QLQ-C30 in patients across the 3 P-QST phenotypes.