There is an association between fatigue and the serum biomarkers macrophage inflammatory protein 1β (MIP1β) and serum vascular endothelial growth factor (VEGF) in patients with ankylosing spondylitis (AS), according to a letter to the editor published in Rheumatology. Authors of this correspondence also noted that the association between fatigue and serum biomarkers was not present among patients with nonradiographic axial spondyloarthritis (nr-axSpA) or mechanical back pain (MBP).
The study in question included blood samples from the Bath Spondyloarthritis Biobank, a longitudinal database of adult patients aged ≥18 years with suspected or confirmed diagnosis of axSpA. At the time of study, the Biobank included 50 mL samples from 1176 patients with confirmed axSpA, 77% of whom had AS. Demographic and clinical information of patients were obtained at routine clinical visits. For each biomarker, the lowest limit of quantitation (LLOQ) was reported; biomarkers with levels below the LLOQ were coded as absent. Fatigue was determined using the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) Q1. Pearson, Chi-squared, Mann-Whitney U, and Kruskal-Wallis tests were used for evaluation where suitable.
The final study cohort included 273 patients, among whom 195 (71.4%) had AS, 27 (9.9%) had nr-axSpA, and 51 (18.6%) had MBP. Compared with 77.8% of the nr-axSpA and 13.7% of the MBP cohort, 88.8% of patients in the AS cohort were human leukocyte antigen B27-positive (P <.01). Compared with the other groups, a greater percentage of patients in the AS group were men (44.4% and 43.1% vs 74.4%; P <.01) and generally older (34.0 and 29.9 years vs 53.8 years, respectively; P <.01). Among patients with AS, fatigue was significantly correlated with serum levels of MIP1β and VEGF; however, this association was not observed among patients with nr-axSpA or MBP. Patients receiving treatment with tumor necrosis factor inhibitors (TNFis) vs those who were not had lower MIP1β levels (506.8 pg/mL vs 625.0 pg/mL; P =.001) and lower fatigue (mean BASDAI Q1 score, 3.7 vs 5.2; P <.001).
These data detected an association between MIP1β and fatigue, which may be ameliorated by treatment with TNFi. Because of the relatively small cohort size and the low percentage of patients receiving TNFi, the investigators emphasized the importance of validation in another cohort. Further study is necessary to explore the mechanisms that underlie fatigue in patients with AS.
Disclosure: One study author declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.
Reilly E, McGrogan A, Sengupta R. Evaluating patient-reported fatigue and serum biomarkers in axial spondyloarthritis. Letter [published online April 7, 2020]. Rheumatology (Oxford). doi:10.1093/rheumatology/keaa115