When brucellosis met the Assessment of SpondyloArthritis international Society classification criteria for spondyloarthritis: a comparative study.

Objectives: To distinguish brucellosis patients fulfilling the Assessment of SpondyloArthritis international Society (ASAS) classification criteria for spondyloarthritis (SpA) from SpA patients.

Methods: Brucellosis patients diagnosed from September 2012 to December 2017 who met the ASAS classification criteria for SpA were analyzed with clinical characteristics and laboratory and imaging examinations. Axial or peripheral SpA patients were respectively included into the comparative analysis with a 4:1 ratio.

Results: Twenty-two brucellosis (10 axial and 12 peripheral) patients (male, 16 cases; 72.72%; mean (S.D.) age, 40.23 (16.49) years) and 88 SpA patients were included. All brucellosis patients had been misdiagnosed or considered as SpA before admission to our center. The brucellosis patients had shorter disease duration (axial, P = 0.001; peripheral, P = 0.108). More than half (59.09%) of the patients had contact history with livestock. The low back pain (LBP) of brucellosis patients was generally less improved with exercise (axial, P = 0.001; peripheral, P = 0.008). More brucellosis patients had myalgia (axial, P < 0.001; peripheral, P = 0.071) or fever (axial, P < 0.001; peripheral, P = 0.107). None of them had positive HLA-B27. Blood culture tests were performed in all brucellosis patients and only 4 (18.18%) were positive. Twenty (90.91%) brucellosis patients were gold-immunochromatographic assay (GICA) positive. Bone marrow edema and bone erosion in sacroiliac joints were respectively detected in 100% (10/10) and 90% (9/10) axial brucellosis patients by MRI. Adjacent muscle involvement was found in 80% (8/10) of the patients.

Conclusions: Indicators including disease duration, contact history of livestock, features of LBP, myalgia, fever, and HLA-B27 can help the differential diagnosis of brucellosis and SpA. GICA test and sacroiliac joints MRI can furtherly confirm the diagnosis of brucellosis.