Pain and pain mechanisms in patients with inflammatory arthritis: A Danish nationwide cross-sectional DANBIO registry survey.

BACKGROUND: Central pain mechanisms may be prominent in subsets of patients with rheumatoid arthritis (RA), psoriatic arthritis (PsA) and other spondyloarthritis (SpA). The painDETECT questionnaire (PDQ) identifies neuropathic pain features, which may act as a proxy for centrally mediated pain. The objectives were to quantify and characterize pain phenotypes (non-neuropathic vs. neuropathic features) among Danish arthritis patients using the PDQ, and to assess the association with on-going inflammation. METHODS: The PDQ was included onto the DANBIO touch screens at 22 departments of Rheumatology in Denmark for six months. Clinical data and patient reported outcomes were obtained from DANBIO. A PDQ-score >18 indicated neuropathic pain features, 13-18 unclear pain mechanism and <13 non-neuropathic pain. RESULTS: Pain data (visual analogue scale, VAS) was available for 15,978 patients. 7,054 patients completed the PDQ (RA: 3,826, PsA: 1,180, SpA: 1,093). 52% of all patients and 63% of PDQ-completers had VAS pain score ≥ 30 mm. The distribution of the PDQ classification-groups (<13/ 13-18/ >18) were; RA: 56%/24%/20%. PsA: 45%/ 27%/ 28%. SpA: 55% / 24%/ 21%. More patients with PsA had PDQ score >18 compared to RA and SpA (p<0.001). For PDQ > 18 significantly higher scores were found for all patient reported outcomes and disease activity scores. No clinical difference in CRP or swollen joint count was found. Logistic regression showed increased odds for having VAS pain ≥39 mm (the median) for a PDQ-score >18 compared to <13 (OR = 10.4; 95%CI 8.6-12.5). CONCLUSIONS: More than 50% of the Danish arthritis patients reported clinically significant pain. More than 20% of the PDQ-completers had indication of neuropathic pain features, which was related to a high pain-level. PDQ-score was associated with DAS28-CRP and VAS pain but not with indicators of peripheral inflammation (CRP and SJC). Thus, pain classification by PDQ may assist in mechanism-based pain treatment.

Non-nociceptive pain in rheumatoid arthritis is frequent and affects disease activity estimation: cross-sectional data from the FRAME study.

BACKGROUND: The painDETECT questionnaire (PDQ) is a mechanism-based pain classification tool assigning patients to one of three categories depending on the quality of the experienced pain. Patients with non-nociceptive pain score high on the PDQ. The objective was to assess the proportions of the three PDQ classification groups in patients with rheumatoid arthritis (RA) and to explore differences in clinical characteristics. METHOD: RA patients initiating or escalating their RA therapy were included prospectively and underwent a thorough examination programme. Low (PDQ score < 13), medium (PDQ score 13-18), and high (PDQ score > 18) scores indicate nociceptive, unclear/possible neuropathic, or neuropathic pain mechanisms, respectively. RESULTS: The 102 included patients were classified into the following PDQ classification groups: low = 65%, medium = 23%, and high = 12%. Patients in the medium and high PDQ groups scored worse on indicators of anxiety, depression, disability, mental health-related quality of life, pain, and fatigue. They also had more tender points and an RA disease activity score based on 28 joints (DAS28) where a higher fraction of the composite score pertained to non-inflammatory factors compared to patients in the low PDQ classification group. There were no differences in objective inflammatory indices across groups. Multiple regression analysis demonstrated that the tender joint count (TJC) and the 36-item Short Form Health Survey (SF36) mental component summary (MCS) score were independently associated with the PDQ score. CONCLUSIONS: In patients initiating or intensifying medical treatment for their RA, non-nociceptive pain (PDQ score ≥ 13) is common. In these patients, the pain mechanisms result in increased disease activity scores on a non-inflammatory basis.