Development of a clinical prediction model for discriminative factors of lower respiratory tract infections in patients presenting with fever: A single-center retrospective study.

OBJECTIVE

To identify clinical risk factors for lower respiratory tract infections (LRTIs) in fever outpatients to help differentiate LRTI from upper respiratory tract infections (URTIs).

METHODS

This single-center cross-sectional study analyzed data from visitors to the fever clinic to identify risk factors for LRTIs using multivariable LASSO-logistic regression. The model's discriminative performance was assessed using the area under the receiver operating characteristic curve (AUROC).

RESULTS

Among 715 patients (173 LRTI, 542 URTI), LRTI patients were older (median 66 vs. 33 years) and more frequently had diabetes (9.2% vs. 2.8%) and hypertension (8.7% vs. 3.3%) (all P < 0.01). Symptoms like cough with sputum (52.0% vs. 40.6%), dyspnea (12.7% vs. 2.8%), diarrhea or vomiting (18.5% vs. 5.0%), appetite loss (6.9% vs. 0.7%), and confusion (5.2% vs. 0.4%) were closely associated with LRTI, while sore throat or nasal congestion was related to upper respiratory tract infections (URTIs) (27.2% vs. 62.7%) (all P < 0.01). LRTI patients had higher white blood cell (WBC) count (9.97 vs. 8.79), neutrophil count (8.22 vs. 6.63) and ratio (81.2% vs. 77.4%), Neutrophil-Lymphocyte Ratio (NLR) value (7.03 vs. 5.37), and C-reactive protein (CRP) level (48.79 vs. 15.26) compared to URTI patients (all P < 0.01). Multivariable logistic regression analysis identified age (OR: 1.043), cough with sputum production (OR: 2.652), diarrhea and vomiting (OR: 2.503), and CRP (OR: 1.009) as independent predictors of fever caused by LRTI (all P < 0.05). The model demonstrated robust performance with an area under curve (AUC) of 0.846, which remained stable upon internal validation (AUC: 0.842).

CONCLUSION

Our discriminative model can assist clinicians in using limited outpatient testing indicators to identify fever patients presenting with LRTI, facilitating timely pharmacological interventions. However, prospective external validation is needed before clinical implementation.