Prognostic value of lactate, lactate clearance, and lactate-to-albumin ratio for predicting 28-day mortality in older patients with sepsis in the emergency department

Older adults with sepsis have a high risk of mortality, and early prognostic biomarkers may facilitate risk stratification in the emergency department (ED). To compare the prognostic performance of lactate, lactate clearance and lactate-to-albumin ratio (LAR) for predicting 28-day mortality in older patients with sepsis. We conducted a retrospective cohort study of older patients (≥ 65 years) presenting with sepsis to the ED at Ramathibodi Hospital between June and December 2023. Initial serum lactate, serum albumin, and follow-up lactate levels at 6 h and 24 h were measured. The primary outcome was 28-day all-cause mortality. The predictive performance of the LAR and lactate clearance was compared using area under receiver operating characteristic (AUROC) curve analysis. Pairwise AUROC comparisons using the DeLong test were performed using complete-case analysis, and decision curve analysis (DCA) to assess clinical benefit. Of 272 older adults screened, 223 met the eligibility criteria. In the complete-case analysis ( n = 176), 6-hour lactate clearance showed the highest discriminative performance (AUROC 0.77, 95% CI 0.66–0.87), comparable to 24-hour lactate clearance (AUROC 0.76) and 6-hour LAR clearance (AUROC 0.76), and significantly better than initial lactate (AUROC 0.58; p = 0.02). Initial LAR (AUROC 0.61) and 24-hour LAR clearance (AUROC 0.54) demonstrated limited discriminative performance. DCA showed greater net clinical benefit for failure to achieve adequate lactate clearance (< 20%) at both 6 and 24 h than treat-all or treat-none strategies across clinical threshold probabilities (10–27%). Dynamic lactate-based biomarkers, particularly 6-hour lactate clearance, demonstrated good prognostic performance. DCA showed greater net clinical benefit for serial lactate monitoring in older patients with sepsis.