[Risk factors for pulmonary hemorrhage and severe infection in leptospirosis patients and construction of a prediction model].

Objective: To investigate the risk factors for pulmonary hemorrhage and severe infection in adult leptospirosis patients and to construct a prediction model. Method: A retrospective analysis was conducted on patients with leptospirosis admitted to the First Affiliated Hospital of Wenzhou Medical University from August 2017 to September 2025. Patients were divided into a non-pulmonary hemorrhage group (n=95) and a pulmonary hemorrhage group (n=63) based on the presence or absence of pulmonary hemorrhage. Multivariate logistic regression model was used to analyze the risk factors for pulmonary hemorrhage and severe infection. A prediction model was constructed and a nomogram was developed. Bootstrap method was used for internal validation of the model, and the area under the receiver operating characteristic curve (AUC), Hosmer-Lemeshow test, calibration curve and decision curve analysis were used to evaluate the model performance. Results: A total of 158 patients (141 males) were enrolled, with the age [M (Q1,Q3)] of 66 (57, 72) years. Among them, 95 (60.1%) were classified as the pulmonary hemorrhage type and 63 (39.9%) were non-pulmonary hemorrhage type. Compared with the non-pulmonary hemorrhage group, the pulmonary hemorrhage group had lower hemoglobin [(96.7±16.2) vs (119.1±18.9) g/L], lower platelet count [32.0 (13.5, 70.5)×10⁹/L vs 95.0 (55.0, 141.0)×10⁹/L], lower albumin level [26.4(24.3,28.4) vs. 29.9(26.9,32.5) g/L] and higher serum creatinine [230.0 (141.5, 342.0) vs 133.0 (87.0, 262.0) μmol/L], with all differences being statistically significant (all P<0.05). Logistic regression model analysis identified a symptom onset-to-admission time exceeding 3 days (OR=2.53, 95%CI: 1.03-6.26, P=0.042), thrombocytopenia (OR=1.80, 95%CI: 1.15-2.81, P=0.010), and hypoproteinemia (OR=3.95, 95%CI: 1.25-12.48, P=0.019) as independent risk factors for pulmonary hemorrhage. On this basis, a diagnostic prediction model incorporating these risk factors together with the degree of anemia was established, with an AUC of 0.886 (95%CI: 0.835-0.937). At the maximum Youden index, the sensitivity and specificity were 80.9% and 82.1%, respectively. The Hosmer-Lemeshow test indicated that all the aforementioned models demonstrated satisfactory calibration (χ2=9.104, P=0.334). The calibration curve indicated good calibration. Decision curve analysis demonstrated a stable net benefit across the clinical decision threshold range of 0.05-0.85. Conclusions: A symptom onset-to-admission time exceeding 3 days, thrombocytopenia, and hypoproteinemia are independent risk factors for pulmonary hemorrhage in adult leptospirosis patients. The prediction model based on these risk factors may facilitate identification of patients at high risk of pulmonary hemorrhage.