Unacceptable pain is common in patients with psoriatic arthritis

A considerable number of patients with psoriatic arthritis (PsA) starting their first biologic treatment report unacceptable pain during the first year of treatment, even when their inflammation is controlled [1]. Among good responders, non-inflammatory pain made up more than 80% of pain load at 3 months, indicating insufficient effects of biologics in patients with inflammation-independent pain. These findings strongly indicate a need for alternative treatment strategies in affected patients.

This study was conducted by Dr Tor Olofsson (Lund University, Sweden) et al. “It is time to shift gears. We will focus on observational studies and old medications instead of randomised controlled trials and new drugs, and we are looking at pain specifically,” said Dr Olofsson. “A swift background; when asked to prioritise between different domains in which patients are most keen on seeing an improvement, in many studies, pain has turned out as the number one. Furthermore, the prevalence of concurrent fibromyalgia is ≥30% in PsA patients compared with about 2% in the general population [2]. Recently, there is also a growing awareness of an uncoupling between pain and inflammation. However, studies of remaining pain have so far mainly been conducted in rheumatoid arthritis. Therefore, we aimed to assess unacceptable pain, despite inflammation being controlled during the year after starting a first TNF inhibitor (TNFi) therapy in PsA patients” said Dr Olofsson.

PsA patients starting a first TNFi treatment (n=352) between 2004 and 2010 were identified in the prospective, observational South Swedish Arthritis Group register. About half of them were women (48%), the mean age was 47 years old, and mean disease duration 10 years. At the onset of TNFi therapy, 63% of patients had ongoing methotrexate and 68% were on any conventional disease-modifying-anti-rheumatic drugs (DMARDs). Unacceptable pain was defined as >40 mm on a VAS of pain (scale 0-100 mm), based on the patient acceptable symptom state (PASS), and concomitant inflammation control was captured through C-reactive protein (CRP) <10 mg/L in combination with <1 swollen joint count. Assessments were performed at baseline, and 1.5, 3, 6, and 12 months after starting TNFi therapy. Analyses were further conducted in relation to EULAR treatment response, after 3 months (good, moderate, no response). Differences in pain measures between treatment response groups were predicted by regression analysis.

At the start of TNFi therapy, 85% of patients reported unacceptable pain, which declined to 43% after 3 months and then remained stable, reaching 39% at 12 months. The proportion of patients who had unacceptable pain despite inflammation control was largely unchanged over the study period (24% at treatment start, 27% at 3 months, and 26% at 12 months). Unacceptable pain at 3 months was strongly related to EULAR 3-month response (24% of good responders vs 79% of nonresponders; P<0.001). This relationship was less pronounced among patients with unacceptable pain despite inflammation control (19% of good responders vers.us 37% of nonresponders; P=0.016). Among EULAR good responders, unacceptable pain irrespective of inflammation control constituted 81% of all unacceptable pain at 3 months. These findings need to be tempered by factors including the fact that the CRP and other inflammatory markers may be normal in PsA and factors such as polyenthesitis that is difficult to recognise and also not associated with elevated inflammatory markers.

1. Roseman C, et al. Abstract OP0112. EULAR 2019.
2. Häuser W, Fitzcharles MA. Dialogues Clin Neurosci. 2018 Mar;20(1):53-62.

Posted on 4 September, 201916 February, 2024