The Predictive Role of C-Reactive Protein, Leukocyte Cell Count, and Soluble Urokinase Plasminogen Activator Receptor for Pulmonary Sequelae in Hospitalized COVID-19 Survivors: A Prospective Single-Center Cohort Study

<b>Background:</b> Pulmonary function impairment significantly affects quality of life, work ability, and healthcare utilization. Among patients with COVID-19, respiratory symptoms vary in severity. This study aimed to assess whether biomarkers related to respiratory function and inflammation at emergency department (ED) admittance can predict long-term pulmonary function impairment in COVID-19 survivors. <b>Methods:</b> This prospective single-center study recruited patients 4-5 months post-COVID-19 infection using consecutive sampling. All attendees at the respiratory outpatient clinic were invited to participate. Pulmonary function tests, including diffusing capacity of the lungs for carbon monoxide (DL_CO), total lung capacity (TLC), forced expiratory volume in the first second (FEV1), and forced vital capacity (FVC), were performed, with DL_CO < 80% as the key indicator of impairment. Baseline biomarkers-C-Reactive Protein (CRP), leukocyte counts, and soluble urokinase Plasminogen Activator Receptor (suPAR)-were correlated with post-discharge DL_CO values. <b>Results:</b> This study enrolled 110 patients with COVID-19; 58.2% were female, the median age was 61.5, and the average BMI was 27.2. Smoking history showed that 53.7% were never smokers, 43.5% were former smokers, and 2.8% were current smokers. A diffusion deficit (DL_CO < 80%) was present in 48.6% of patients. Leukocyte counts and suPAR had the highest sensitivity (>0.80) for predicting DL_CO impairment but showed low specificity and a positive predictive value (PPV) of around 0.50. However, combining all biomarkers improved prediction accuracy, with a negative predictive value (NPV) of 0.93. <b>Conclusions:</b> The chosen inflammatory biomarkers by themselves had a limited ability to predict long-term pulmonary function impairment in COVID-19 survivors. However, when combined, they demonstrated a high negative predictive value (NPV) for identifying DL_CO impairment. This strategy could help clinicians better tailor follow-up care for patients with COVID-19.