Over 40% of Patients With Inflammatory Arthritis Have Pain Due to Nonsynovial Inflammation

Pain due to nonsynovial inflammation is common among patients with inflammatory arthritis (IA), according to study results published in Seminars in Arthritis & Rheumatism.

Around 40% of patients with IA report persistent pain despite receiving treatment with disease-modifying antirheumatic drugs.

Researchers conducted a systematic review and meta-analysis to assess the contribution of pain sensitivity and neuropathic-like pain to persistent pain in the setting of IA. To that end, investigators from King’s College London in the United Kingdom searched publication databases through June 2022 for relevant studies. Both pain sensitivity and neuropathic-like pain were defined using validated questionnaires, such as the Central Sensitization Inventory (CSI), Douleur Neuropathique 4 Questions (DN4), Leeds Assessment of Neuropathic Symptoms and Signs (LANSS), and the painDETECT Questionnaire (PDQ).

This analysis included a total of 63 studies comprising 13,035 patients. The studies enrolled patients with rheumatoid arthritis (RA; n=38), spondylarthritis (SpA; n=23), and psoriatic arthritis (PsA; n=8).

In the pooled analysis, pain sensitivity or neuropathic-like pain in IA was reported to be 42% using the CSI, 36% using the PDQ, 32% using the LANSS, and 31% using the DN4. Stratified by type of IA, fewer patients with RA reported neuropathic-like pain compared with PsA (P =.002) or SpA (P =.01) according to the PDQ instrument.

In RA, the pooled prevalence of pain ranged between 29.52% (I2=86.69%) defined by PDQ to 37.28% (I²=94.68%) defined by CSI. In SpA, the pooled prevalence of pain ranged between 27.63% (I²=90.63%) defined by DN4 to 48.35% (I²=46.72%) defined by CSI. In PsA, the pooled prevalence of pain ranged between 19.40% defined by DN4 to 52.60% defined by LANSS.

Patients who reported pain sensitivity or neuropathic-like pain also reported greater visual analogue scale (VAS) pain scores and had higher tender joint counts as well as greater disability scores and poorer quality of life scores.

Stratified by treatment response, one study in RA reported that responders had a prevalence of PDQ-defined neuropathic pain of 7% compared with 25% among nonresponders. Other studies reported conflicting evidence about whether the presence of pain predicted treatment response.

Study limitations include the fact that many studies (n=25) were conference abstracts, not peer-reviewed studies, and most studies had a small sample size between 50 and 200 individuals.

“The prevalence of pain sensitivity and/or neuropathic like pain, reported here to be around 31-42% in inflammatory arthritis is much higher than the pain sensitivity prevalence of about 5% reported in the general population,” the study authors noted. “Pain sensitivity and neuropathic like pain is related to higher disease activity, functional disability, poor quality of life and worse mental health. This review highlights the large proportion of patients with IA who may experience pain due to underlying mechanisms other than, or in addition to, synovial inflammation.”