A novel diagnostic model for brucellosis spondylitis using serum PINP and inflammatory factors: a dual-cohort study from Northwest China

While the diagnosis of brucellosis spondylitis (BS) currently relies on imaging, this approach can delay critical intervention. Therefore, identifying novel serum biomarkers is essential to enable earlier diagnosis and prompt antibacterial treatment. A retrospective analysis was conducted on 78 patients with brucellosis, who were categorized into two groups: those with spondylitis (BS group) and those without (NBS group). We measured plasma levels of the bone turnover markers PINP and CTX-I, along with the inflammatory cytokines TNF-α and IL-1β. Subsequently, univariate and multivariate analyses were performed to identify independent risk factors for BS, which were then incorporated into a logistic regression-based diagnostic model. The performance of this model was evaluated. Comparative analysis revealed significantly elevated plasma PINP levels but decreased IL-1β levels in the BS group relative to the NBS group, whereas no significant intergroup differences were observed in CTX-I or TNF-α levels. A diagnostic model incorporating age, low back pain, ESR, CRP, PINP, and IL-1β was subsequently developed. This model demonstrated strong discriminatory power, with an area under the curve (AUC) of 0.958 (95% CI: 0.915–1.000, P < 0.001) in the derivation cohort. During prospective validation, it maintained an AUC of 0.798 (95% CI: 0.641–0.955), with a specificity of 86.8% and a negative predictive value of 90.4%, despite a sensitivity of 50.0% and a positive predictive value of 46.2%. Our study identified significantly elevated plasma PINP levels in BS patients, forming the basis of a diagnostic model with considerable clinical potential. Nevertheless, further validation through prospective, multi-center studies with larger cohorts is essential to confirm its generalizability.