Prevalence of Neuropathic Pain in Patients with Rheumatoid Arthritis

Abstract

Objective: To study the prevalence of possible neuropathic pain in patients with rheumatoid arthritis (RA) in addition to investigating the correlation between disease duration and occurrence of neuropathic pain. Methods: A questionnaire containing Brief Pain Inventory by Dr. Cleeland translated into Chinese was given to patients with RA in the rheumatologic outpatient department from March 2008 to June 2008 in a tertiary center in southern Taiwan. Objective sensory testing was also carried out with results recorded in the questionnaire. Latest level of serological markers for inflammation, erythrocyte sedimentation rate and C-reactive protein, of the patient were documented for investigation on possible correlation. Results: One hundred patients fulfilling the 1987 revised criteria of the American College of Rheumatology for RA participated. Twenty-five patients were excluded due to insufficient background information for analysis. Of the seventy-five patients analyzed, female patients predominated (62 female, 84%), mean age was 55.64 years, average disease duration was 11.08 years, and 67/75 (89.33%) of the patients reported pain within one week prior to the clinic visit. Among the sixty-seven patients complaining of pain, they rated their worst pain intensity as 5.74 (range 1 to 10) on a numeric rating scale, with least pain intensity as 1.78 (range 0 to 9), and pain intensity most of the time as 3.54 (ranged 0 to 10). Among the 67 RA patients complaining of pain upon query, their average disease duration was 11.19 years; allodynia and altered pinprick threshold were found in 40 patients (59.70%) and 47 patients (70.15%), respectively. Conclusion: Review of the literature states allodynia and altered pinprick threshold to be pathognomonic of neuropathic pain. 53 of the 67 patients (79.10%) complaining of pain showed positive for at least one objective sensory test. Nearly 80% of patients have neuropathic pain. Our study found that disease duration of RA does not correlate well with occurrence of allodynia or altered pinprick threshold. Patients with 2-year duration of RA may demonstrate a positive result for both allodynia and altered pinprick threshold; however, eight out of our seventy-five study subjects (10.1%) with over a 10-year disease duration (range 10-40 years) were negative for both.