Supplementary file 1_LDAR shows more consistent prognostic performance than other albumin-derived indices for 28-day ICU mortality in critically ill patients with urosepsis: evidence from a dual-cohort retrospective study.docx

LASSO-selected features trained a multilayer perceptron (MLP), benchmarked against six severity scores; a parsimonious external model (events per variable ≥ 10) was also examined.</p>Results<p>In the derivation cohort, logLDAR, RAR, TAR, AGAR, and UAR were independently associated with 28-day ICU mortality in fully adjusted models (HRs = 1.292, 1.147, 1.136, 1.074, and 1.013, respectively; all P < 0.01), whereas logGAR was not.

Fine-Gray models corroborated these findings (logLDAR sHR = 1.351, 95% CI: 1.238–1.473). RCS revealed a non-linear logLDAR–mortality relationship (P non-linear = 0.040), with risk accelerating beyond logLDAR > 7. logLDAR yielded the highest AUC (0.638, 95% CI: 0.609–0.667) and cNRI (0.119). External validation confirmed the independent prognostic value of logLDAR (HR = 1.524, 95% CI: 1.225–1.895; Fine-Gray sHR = 1.545, 95% CI: 1.295–1.844), with an external AUC of 0.735 (95% CI: 0.648–0.808), although between-cohort differences in case definitions may partly contribute.

The MLP with eight LASSO-selected features achieved an external AUC of 0.762 (95% CI: 0.687–0.840), comparable to SOFA plus logLDAR (AUC = 0.782; DeLong P = 0.512). SHAP analysis ranked logLDAR among the top predictors.</p>Conclusion<p>Among the six albumin-derived indices, logLDAR demonstrated the most consistent and generalizable prognostic performance for 28-day ICU mortality in urosepsis, reflecting both tissue hypoxia and nutritional-inflammatory depletion, and remained robust under competing-risk adjustment. logLDAR may serve as a simple bedside biomarker for early risk stratification; however, prospective studies are warranted to determine whether interventions targeting its underlying pathways can improve outcomes.</p>