Background Axial spondyloarthritis (axSpA) comprises a heterogeneous group of diseases which predominantly involve the axial skeleton and have many overlapping clinical features. The axial SpA spectrum ranges from non-radiographic axial SpA (nr-axSpA) at one end to ankylosing spondylitis (AS) at the other. Chronic low back pain (LBP) is the presenting symptom in the majority of patients with axSpA. Different studies have revealed that 16 to 54% of patients with chronic LBP may have neuropathic pain (NeP) component. Although there is no gold standard for the diagnosis of NeP, use of neuropathic pain screening tools, and quantitative sensory testing may offer the reliable way to diagnose NeP.
Objectives The aim of this study was first to assess NeP component in patients with axSpA, including nr-axSpA and AS; and secondly to assess potential interactions between NeP component and other variables and outcome measures.
Methods Adult patients who met Assessment of SpondyloArthritis International Society (ASAS) axSpA classification criteria were consecutively recruited. Patients with a previous diagnosis or under treatment for NeP, or having diseases causing increased risk to develop neuropathic disorders like uncontrolled diabetes, neuro-endocrine or neuro-vascular disorders were excluded. Patients were examined and evaluated for disease specific and generic outcome measures including disease activity parameters, physical functions, psychological status and health related quality of life measures. Neuropathic component of pain was evaluated using the DN4 interview and PainDetect questionnaire which were applied by the same experienced physician who was unaware of patients' other clinical and outcome data. Patients with a score ≥4 in DN4 were considered as “probable NeP” and ≥13 in PainDetect were considered as “possible or likely NeP”. Clinical variables and outcome measures were compared patients with NeP and without NeP component according to two different criteria.
Results One hundred and seven patients (51.4% male, 48.6% female) with axSpA (36 nr-axSpA, 71 AS) were included (mean age 35.9±10.2). The first presenting symptom was LBP in 80% of the patients. NeP component was present in 31.8% of patients with axSpA categorized according to DN4 (33.3% in nr-axSpA vs 31.0% in AS, p=0.805) and in 34.6% of patients categorized according to PainDetect (36.1% in nr-axSpA vs 33.8% in AS, p=0.813). Pain characteristics like burning, electric shock, tingling, pins and needles, itching, numbness and painful cold as well as pain course were quite similar between patients with nr-axSpA and AS. Patients with NeP component according to two assessment tools had significantly higher scores in VAS-pain, fatigue, BASDAI, ASDAS-CRP and poorer QoL and physical functions compared to patients with nonNeP. However after adjusting for confounding variables in a multivariable logistic regression analysis NeP was associated only with ASQoL (OR 1.14; 95% CI 1.05–1.25) in DN4 categorized and VAS-fatigue (OR 1.32; 95% CI 1.07–1.62) in PainDetect categorized patients.
Conclusions This is the first study showing that nearly one third of patients with axSpA may have NeP component regardless of having nr-axSpA or AS. NeP component may contribute worsened QoL and fatigue and should be kept in mind while targeting the management.
Disclosure of Interest None declared