Diagnostic value of serum markers and C-reactive protein of joint fluid in purulent arthritis.

Introduction: Predicting purulent arthritis with a single marker may result in low sensitivity and specificity. We investigated the diagnostic value of serum markers and joint fluid C-reactive protein (CRP) in purulent arthritis.

Methodology: A total of 183 patients with acute joint infection, who were treated at our hospital between April 2019 and September 2022, were retrospectively analyzed via convenient sampling. Serum markers and joint fluid CRP levels were compared between the infection group and the control group to assess their early diagnostic value.

Results: Based on multivariate analysis, delta neutrophil index, DNI (odds ratio (OR) = 8.428, 95% confidence interval (CI): 4.753-9.134, p < 0.001); erythrocyte sedimentation rate, ESR (OR = 1.981, 95% CI: 1.435-4.123, p < 0.001); procalcitonin, PCT (OR = 2.418, 95% CI: 1.575-5.639, p < 0.001); serum CRP (OR = 2.784, 95% CI: 1.982-4.243, p < 0.001); and joint fluid CRP (OR = 3.279, 95% CI: 2.142-5.510, p < 0.001) were identified as risk factors for purulent arthritis. Predictive value assessment showed that the DNI, ESR, PCT, serum CRP, and joint fluid CRP all held a predictive value for purulent arthritis (p < 0.05), with the highest predictive value in the combination of all five markers, yielding an area under the curve (AUC) of 0.922 (95% CI: 0.854-0.962).

Conclusions: The DNI, ESR, PCT, serum CRP, and joint fluid CRP are crucial diagnostic indicators for identifying acute purulent arthritis. Notably, joint fluid CRP demonstrated the highest predictive value among the indicators.