To compare clinical characteristics and patient-reported outcomes in seropositive versus seronegative primary Sjögren's syndrome (SS) patients and to investigate the effect of serologic status on the prevalence of chronic pain, comorbidity, and health quality.
Pain severity and neuropathic pain symptoms, comorbidity, and health status were assessed in 108 primary SS patients. Differences between patient groups were assessed by t-test and chi-square test, as well as adjusted pain-affect associations. The effect of predictor variables on pain severity was examined with multivariate regression.
Pain severity was greater (P = 0.003) and physical function (P = 0.023) was reduced in the seronegative patients. Prevalence of neuropathic pain, depression, anxiety, and disability was similar between groups. Chronic pain, defined as daily pain for >3 months, was reported by 65% of seropositive (n = 65) and 75% of seronegative (n = 40) patients. After adjustment for age, sleep quality, and psychological distress, the difference in pain severity between seropositive and seronegative patients remained significant.
Chronic pain is pervasive in both seropositive and seronegative primary SS patients, while pain severity and functional impairment are greater in seronegative patients. Neuropathic pain is equally prevalent and is the predominant pain phenotype in patients with moderate to severe pain. Accurate assessment of pain phenotypes is needed for more effective management of chronic pain in primary SS. The focus of future research should be to standardize assessment of pain and to identify the factors contributing to more severe pain in seronegative patients.