Serum lactate dehydrogenase as a prognostic marker for 90-day mortality in connective tissue disease patients receiving glucocorticoids and hospitalized with pneumonia: a cohort study

Elevated serum lactate dehydrogenase (LDH) levels have been associated with poor prognosis in various diseases. This study investigates the relationship between serum LDH levels and 90-day mortality in patients with connective tissue disease (CTD) receiving glucocorticoids and hospitalized with pneumonia. A total of 298 CTD patients were included in this study. The cohort was divided into three groups based on serum LDH levels (Group 1: < 246 U/L, 0% mortality; Group 2: 246-407 U/L, 26% mortality; Group 3: ≥ 407 U/L, 48% mortality). Clinical and laboratory data were analyzed to evaluate the association between LDH levels and 90-day mortality using Kaplan-Meier survival curves, Cox regression models, and subgroup analyses. Elevated LDH levels were significantly associated with increased mortality. The Kaplan-Meier survival analysis demonstrated that patients in Group 3 (highest LDH levels) had the highest 90-day mortality rate, while those in Group 1 (lowest LDH levels) had the lowest (p < 0.0001). Multivariate Cox regression analysis revealed that every 100 U/L increase in LDH was associated with a higher risk of mortality (HR 1.07, 95% CI 1.01-1.13, p = 0.02). Patients in Group 3 showed a significantly increased risk of mortality (HR 2.29, 95% CI 1.06-4.96, p = 0.036). The subgroup analyses demonstrated stable results across different clinical subgroups. Elevated serum LDH levels, particularly in Group 3, are independently associated with increased 90-day mortality in CTD patients receiving glucocorticoids and hospitalized with pneumonia. LDH may serve as an important prognostic marker for these patients.