Abstract: Objective To describe the clinical characteristics of brucellosis with or without spondylitis and to explore the risk factors for spondylitis in patients with brucellosis, thereby providing a basis for early identification and clinical intervention of brucellar spondylitis. Methods A total of 109 patients with brucellosis hospitalized from 2015 to 2024 were enrolled. According to the presence or absence of imaging-confirmed spondylitis, they were divided into the simple brucellosis group(n=50)and the brucellar spondylitis group(n=59). Demographic data, clinical manifestations, laboratory findings, and imaging features were collected. The clinical characteristics of the two groups were described, and the risk factors for spondylitis in patients with simple brucellosis were identified through binary logistic regression analysis. Results Among the 109 patients, 81 were males and 28 were females, with the age of onset of 56(47.5, 63.5)years. The most common clinical manifestations of brucellosis were fever, low back pain, and fatigue. There were statistically significant differences between the two groups in the incidences of low back pain, radiating pain in the lower limbs, numbness in the upper/lower limbs, sweating/night sweats, and headache. Compared with the simple brucellosis group, the brucellar spondylitis group had a higher proportion of patients in the subacute and chronic stages. The levels of aspartate aminotransferase(AST)and total bilirubin(TBIL)in the brucellar spondylitis group were lower than those in the simple brucellosis group, while the serum calcium level was higher, with statistically significant differences. The overall positive rate of blood culture was 35.8%, and the positive rate in the simple brucellosis group was higher than that in the brucellar spondylitis group(56.0% vs. 18.6%, P<0.001). Brucellar spondylitis most commonly involved the lumbar spine(68.5%), with the L4-L5 vertebrae being the most frequently affected. The length of hospital stay in the brucellar spondylitis group was longer than that in the simple brucellosis group ［11(7,16)days vs. 6(4,10)days, P<0.001］. Binary logistic regression analysis showed that low back pain(OR=28.918, 95%CI: 8.057-103.789), negative blood culture(OR=0.219, 95%CI: 0.065-0.740), and low AST level(OR=0.960, 95%CI: 0.923-0.998)were independent risk factors for spondylitis in patients with simple brucellosis. A prediction model for brucellar spondylitis was established: Logit(P)=-1.597+3.364×low back pain(no=0, yes=1)-1.519×blood culture(negative=0, positive=1)-0.041×AST. The model had a sensitivity of 94.9%, a specificity of 74.0%, and a cut-off value of 0.343. Conclusion The most common clinical manifestations in patients with brucellosis are fever, low back pain, and fatigue. Spondylitis is an important complication of brucellosis, with lumbar spine lesions(mainly L4-L5)being the most common, and low back pain is the most frequent symptom. Low back pain, negative blood culture, and low AST level are independent risk factors for spondylitis in patients with simple brucellosis.

Key words: Brucellosis, Spondylitis, Imaging, Risk factors