Comparison of urine and blood NGAL for early prediction of delayed graft function in adult kidney transplant recipients: a meta-analysis of observational studies

Background Neutrophil gelatinase-assoicated lipocalin (NGAL) appears to be a promising proximal tubular injury biomarker for early prediction of delayed graft function (DGF) in kidney transplant recipients. However, its predictive values in urine and blood were varied among different studies. Here, we performed the meta-analysis to compare the predictive values of urine NGAL (uNGAL) and blood NGAL (bNGAL) for DGF in adult kidney transplant recipients. Methods We systematically searched Medline, Cochrane library and Embase for relevant studies from inception to May 2018. The summary receiver operating characteristic (SROC) curves, the pooled sensitivity, specificity and diagnostic odds ratio (DOR) were used to evaluate the prognostic performance of uNGAL and bNGAL for the identification of DGF. Results A total of 1036 patients from 14 eligible studies were included in the analysis. 8 studies focused on NGAL in urine and 6 reported NGAL in serum or plasma. The composite area under the ROC (AUC) for 24 h uNGAL was 0.91 (95% CI, 0.89-0.94) and the overall DOR for 24 h uNGAL was 24.17(95% CI, 9.94-58.75) with a sensitivity of 0.88 (95% CI, 0.75-0.94) and a specificity of 0.81 (95% CI, 0.68-0.89). The composite AUC for 24 h bNGAL was 0.95 (95% CI, 0.93-0.97) and the overall DOR for 24 h bNGAL was 43.11 (95% CI, 16.43-113.12) with a sensitivity of 0.91 (95% CI, 0.81-0.96) and a specificity of 0.86 (95% CI, 0.78-0.92). Conclusions Urine and serum/plasma NGAL were valuable biomarkers for early identification of DGF in kidney transplantation. In addition, the bNGAL was superior to uNGAL in early prediction of DGF.