Neuropathic pain in axial spondyloarthropathy is underdiagnosed and a confounding factor in biologic drug–switching decision: a cross-sectional study

Objectives The aim of this study was to evaluate the relationship between the presence of neuropathic pain (NeP), disease activity scores and biologic drug–switching decisions in the subjects with axial spondyloarthritis (axSpA) receiving biologic treatment. Methods PainDETECT Questionnaire was used to evaluate the presence of NeP in the patients with axSpA aged ≥18 years who had been receiving biologic treatment for at least 6 months. The relationships between disease activity scores, inflammatory markers, life quality index, biologic drug–switching decisions and the presence of NeP were analyzed. Results A total number of 175 patients with axSpA [ankylosing spondylitis (AS) (n:150) and non-radiographic axSpA (nr-axSpA) (n:25)] were enrolled in the study. NeP was detected in 41.7% of the patients and it was more common in females than in males (p:0.009). PainDETECT scores were positively correlated with disease activity scores, but they were not correlated with inflammatory marker levels. NeP was found to be significantly more common in whom the biologics had been switched 3 or more times (p:0.007). PainDETECT scores were higher and NeP was more prevalent (p:0.028) in the patients for whom drug-switching decisions had been made due to primary or secondary unresponsiveness. Conclusion NeP is more common than estimated in the patients with axSpA and current disease activity scores are insufficient to make a distinction between NeP and inflammatory pain. NeP is a confounding factor in the evaluation of treatment response to biologic agents. In the subjects with AS and nr-axSpA with primary or secondary treatment unresponsiveness, the presence of NeP must be considered before biologic drug–switching decisions. Key Points • Neuropathic pain (NeP) is common in subjects with AxSpA treated with multiple biologic agents. • Current disease activity scores for AxSpA are insufficient to make a differentiation between NeP and inflammatory pain. • NeP is a confounding factor in the evaluation of treatment response to biologic agents. • Patients with AxSpA should be re-evaluated in terms of the presence of neuropathic pain before making biologic drug-switching decisions.