Central pain mechanisms are seen prominent in patients with rheumatoid arthritis (RA), psoriatic arthritis (PsA) and other spondyloarthritis (SpA). The pain DETECT questionnaire (PDQ) identifies neuropathic pain features, which may act as a proxy for centrally mediated pain.

Rifbjerg-Madsen S et al. conducted a descriptive, cross-sectional survey to quantify and characterise the pain phenotypes (non-neuropathic vs neuropathic features) among Danish arthritis patients. This was done through the PDQ, and to assess the association with on-going inflammation.

The current study involved patients registered in DANBIO, the Danish nationwide rheumatologic registry. 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.

The pain data (visual analogue scale, VAS) obtained of 15,978 patients. PDQ completed by 7,054 patients (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).

Overall, the study concluded that clinically significant pain was reported by more than 50% of Danish arthritis patients. More than 20% of the PDQ-completers indicated neuropathic pain features, which was related to a high pain-level. PDQ-score was associated with DAS28-CRP and VAS pain but was not indicative of peripheral inflammation (CRP and SJC). Thus, pain classification by PDQ may help manage them in the mechanism-based pain management approach.