Lactate/Albumin Ratio and Mortality in Respiratory Failure

Acute respiratory failure is a common cause of intensive care unit (ICU) admission and is associated with high short-term mortality. Early risk stratification is important for guiding treatment intensity and resource allocation. Serum lactate reflects tissue hypoperfusion and impaired oxygen utilization, whereas serum albumin is a marker of nutritional status, systemic inflammation, and capillary leak. The lactate-to-albumin ratio (LAR) combines these two readily available laboratory parameters and has been proposed as a prognostic marker in critically ill patients. However, its prognostic value in patients with acute respiratory failure has not been well established.

This is a single-center, retrospective observational cohort study conducted at Kocaeli City Hospital, including adult patients (≥18 years) admitted to the ICU with acute respiratory failure between April 2023 and June 2026. Data will be obtained from the hospital information system and ICU records.

The primary objective is to evaluate the association between LAR at ICU admission and 28-day all-cause mortality. The secondary objective is to compare the prognostic performance of LAR with that of serum lactate alone, serum albumin alone, and established severity scores (e.g., APACHE II, SOFA).

The following data will be collected: demographic characteristics, comorbidities, cause of respiratory failure, need for invasive mechanical ventilation, severity scores, laboratory parameters (including lactate and albumin measured at ICU admission), ICU and hospital length of stay, and 28-day survival status. LAR will be calculated as serum lactate (mmol/L) divided by serum albumin (g/dL).

Patients will be grouped as survivors and non-survivors at 28 days. The association between LAR and mortality will be assessed using logistic regression and/or Cox proportional hazards models adjusted for relevant confounders. Discriminative ability will be evaluated with receiver operating characteristic (ROC) curve analysis, and the optimal cut-off value will be determined. AUC values of LAR and the comparator parameters will be compared.