The role of lactate dehydrogenase in hospitalized patients, comparing those with pulmonary versus non-pulmonary infections: A nationwide study

BACKGROUND: Lactic dehydrogenase reflects target organ damage, and is associated with mortality in patients with infectious diseases. OBJECTIVE: The purpose of this study was to examine associations of serum lactic dehydrogenase levels with mortality, target organ damage and length of hospital stay in adults with pulmonary and non-pulmonary infections. METHODS: This nationwide retrospective cohort study comprised patients admitted with infections, to medical and surgical departments in eight tertiary hospitals during 2001–2020. Patients with available serum lactic dehydrogenase levels on admission and one week after were included, and stratified by the source of their infection: pulmonary vs. non-pulmonary. Associations of lactic dehydrogenase levels with mortality and target organ damage were analyzed using multivariable logistic regression models. Quantile regression was used for multivariable analysis of the median length of stay. RESULTS: The study included 103,050 patients (45.4% male, median age: 69 years); 44,491 (43.1%) had pulmonary infections. The median serum lactic dehydrogenase levels on admission were higher in patients with pulmonary than non-pulmonary infections (418 vs. 385 units per liter (U/L), p<0.001). In a multivariable logistic regression model, elevated serum lactic dehydrogenase levels (480–700 U/L, 700–900 U/L and >900 U/L), compared with <480 U/L, were associated with in-hospital mortality (OR = 1.81, 2.85 and 3.69, respectively) and target organ damage (OR = 1.19, 1.51 and 1.80, respectively). The median stay increased with increasing elevated lactic dehydrogenase levels (+0.3, +0.5 and +0.4 days, respectively). Among patients with lactic dehydrogenase levels >900 U/L, mortality, but none of the other examined outcomes, was greater among those with pulmonary than non-pulmonary infections. CONCLUSIONS: Among hospitalized patients with infectious diseases, lactic dehydrogenase levels were associated with mortality and target organ damage, and were similar in patients with pulmonary and non-pulmonary infections. Among patients with lactic dehydrogenase levels >900 U/L, mortality was prominently higher among those with pulmonary than non-pulmonary infections.