# Soluble DLL1 as an Indicator of acute kidney injury and postoperative delirium following cardiac surgery: a secondary analysis of a prospective study

## TL;DR

This study explores if sDLL1 levels can predict kidney injury and delirium after heart surgery, finding moderate predictive value for both outcomes.

## Contribution

The novel contribution is demonstrating sDLL1's potential as a biomarker for both AKI and postoperative delirium following cardiac surgery.

## Key findings

- sDLL1 levels were significantly higher in patients with AKI compared to those without.
- sDLL1 showed moderate predictive value for identifying postoperative delirium (AUCROC 0.72).
- sDLL1 elevation was independent of cardiopulmonary bypass type, suggesting a general inflammatory response.

## Abstract

Acute kidney injury (AKI) displays a common complication after cardiac surgery and must be diagnosed as early as possible. Soluble delta-like protein 1 (sDLL1) was originally evaluated as a sepsis biomarker but might also indicate other adverse outcomes. This study aims to investigate sDLL1 levels, examining its potential relationship with AKI and postoperative delirium (POD) after cardiac surgery and its predictive value.

This secondary analysis of a prospective observational trial included elective cardiac surgery patients. ELISA was used for the quantification of sDLL1. Statistical analysis involved repeated measures ANOVA and Pearson’s correlation to assess associations between sDLL1 levels, renal, and inflammatory parameters. Receiver operating curves were used for prediction analysis.

Ninety patients were included in the study. Compared to patients without AKI, those with AKI (6.1%) showed significantly elevated plasma levels of sDLL1 postoperatively (no AKI 6308.49 [5121.27–7955.28], AKI 7,714.77 [7151.06–10,514.73] ng/mL; p = 0.01). Postoperative sDLL1 levels showed only a low predictive value for AKI (AUCROC 0.63, sensitivity 0.91, specificity 0.53). Postoperative sDLL1 measurements were also significantly elevated in patients with POD (23.3%). Further, postoperative sDLL1 plasma levels showed a moderate prediction for the identification of POD (AUCROC 0.72, sensitivity 0.64 specificity 0.73).

This study demonstrates that sDLL1 provides moderate predictive value for AKI and POD after cardiac surgery and may provide valuable insights into postoperative complications. sDLL1 levels increase independently of CPB type, suggesting a role in the inflammatory response to the cardiopulmonary bypass and surgical stress rather than specific renal injury.

DRKS00010959.

The online version contains supplementary material available at 10.1186/s13741-025-00570-4.