Urine NGAL as an early biomarker for diabetic kidney disease: accumulated evidence from observational studies

Objectives: Urine neutrophil gelatinase-associated lipocalin (NGAL) was found to increase in diabetic kidney disease (DKD). However, the clinical value of urine NGAL as diagnostic indicators in DKD remains to be clarified. Methods: Relevant studies were systematically retrieved from PubMed, Embase, Web of Science, and the Cochrane Library. Stratified analyses and regression analyses were performed. Results: Fourteen studies with 1561 individuals were included in our analysis, including 1204 cross-sectional participants and 357 cohort participants. For the cross-sectional studies, the pooled sensitivity and specificity of NGAL in the diagnosis of DKD were 0.82 (95% confidence interval (CI): 0.75–0.87) and 0.81 (95% CI: 0.68–0.90), respectively. The pooled diagnostic odds ratio was 19 (95% CI: 11–33), and the overall area under the curve was 0.88 (95% CI: 0.84–0.90). For the cohort studies, the pooled sensitivity and specificity of NGAL in the diagnosis of DKD were 0.96 (95% CI: 0.91–0.98) and 0.89 (95% CI: 0.84–0.92), respectively. The overall area under the curve was 0.98, indicating good discriminative ability of NGAL as biomarkers for DKD. Conclusions: Urine NGAL, as the early diagnostic marker of DKD, might have the high diagnostic value, especially in cohort studies.