LEIA was used to determine the concentration of plasma NGAL according to the Clinical and Laboratory Standards Institute (CLSI) standardization evaluation protocal. The imprecision, recovery rate, linear range, anti-interference and stability were assessed. The plasma NGAL levels of 86 patients with type 2 diabetes mellitus (T2DM), including 41 patients with diabetic nephropathy(DN), and 40 healthy subjects (healthy control group) were determined.

The within-run coefficients of variation(CV) for low and high levels of NGAL were 3.76% and 1.79%, respectively. The inter-day CV were 6.62% and 3.45%, respectively. The average recovery rate was 97.3%-104.6%. The linear range was from 0 to 5 000μg/L, and the deviation was < 8%. Comparing with similar foreign kit (particle-enhanced immunoturbidimetric assay), the correlation was high (R²=0.996 6). The system biases of 200 μg/L and 700 μg/L were 3.66 μg/L and 11.79 μg/L, respectively. The results met the requirements of manufacturers. There was no significant interference on the determination of plasma NGAL with total bilirubin≤600 μmol/L, hemoglobin≤10 g/L, vitamin C≤0.6 g/L and triglyceride≤15 mmol/L. The reagent could be stable for 35 d in the instrument under the condition of 2-8 ℃. The plasma levels of NGAL in healthy control group were all in manufacturers' reference range. The level of plasma NGAL had been gradually increasing in healthy control group, T2DM group and DN group with statistical significance (P<0.01). The plasma NGAL were positively correlated with serum cystatin C (Cys C) and creatinine (Cr) (correlation coefficients were 0.58 and 0.43, P<0.01).

The LEIA for plasma NGAL determination has high sensitivity and precision, which is fast and easy to operate, and can be used directly on the automatic biochemical analyzer. The results are accurate and reliable. It is suitable for the clinical application for mass determination.