Evaluation of the presence of neuropathic pain and/or central sensitization in patients with radiographic axial spondyloarthritis followed at a tertiary hospital

Chronic pain (CP) in radiographic Axial Spondyloarthritis (r-axSpA) is primarily peripheral nociceptive pain. However, many patients experience persistent pain despite treatment, suggesting other underlying mechanisms, such as central sensitization (CS) and neuropathy. This study assessed the presence of CS and/or neuropathic pain (NP) in r-axSpA patients treated at a University Hospital in the state of Paraiba. This quantitative, descriptive, and cross-sectional observational study used a convenience sample collected over 24 weeks. Instruments included the Central Sensitization Inventory - CSI (positive score ≥ 40); The PainDETECT Questionnaire - PD-Q (positive score ≥ 19); clinical epidemiological questionnaires, and preliminary diagnostic for fibromyalgia (FM) [American College of Rheumatology criteria of 2010/2011, revised in 2016], applied when CS positive. Inclusion criteria: patients diagnosed with r-axSpA; aged ≥ 18. Analyses performed: Descriptive; univariate and multivariate linear regressions; Student’s T-test. This study included 52 patients (34 men and 18 women), of whom 61.54% had CS. Among these, 65.62% had FM, with an average widespread pain index of 7.87. NP was present in 17.31%, and 15.38% had both CS and NP. The CSI showed a positive correlation with Bath Ankylosing Spondylitis Disease Activity Index - BASDAI (r = 0.574) and Axial Spondyloarthritis Disease Activity Score - ASDAS (r = 0.622), while the PD-Q was positively correlated with BASDAI (r = 0.515) and ASDAS (r = 0.551). In the univariate analysis, CSI was a predictor (p < 0.001) of both BASDAI and ASDAS, with 40.63% of patients scoring BASDAI ≥ 4 and 43.75% scoring ASDAS ≥ 2.1. Additionally, 66.67% of patients with PD-Q ≥ 19 had BASDAI ≥ 4 and 55.56% had ASDAS ≥ 2.1. The PD-Q was a predictor of BASDAI and ASDAS (p < 0.001). This study is the first in the Brazilian scientific literature to investigate and demonstrate the occurrence of CS and/or NP in patients with r-axSpA, even when adequately treated. Another finding considered relevant was the demonstration of the presence of CS in 34.38% of patients who did not meet preliminary criteria for the diagnosis of FM, emphasizing the importance of investigating other painful mechanisms in chronic inflammatory joint diseases. These findings represent a first step for future research, in larger samples and in other forms of axial spondyloarthritis.