Establishment of a time‐resolved immunoassay for acute kidney injury based on the detection of Kim‐1

Aim To establish a highly sensitive time‐resolved fluorescence immunoassay (TRFIA) of kidney injury molecule‐1 (Kim‐1) and evaluate its clinical value in acute kidney injury (AKI). Methods The Kim‐1‐TRFIA was established by the double‐antibody sandwich method, and the method was evaluated. The established Kim‐1‐TRFIA was used to detect the concentration of Kim‐1 in the serum of healthy controls and patients with AKI. Results The optimal coating antibody concentration and optimal Eu 3+ ‐labeled antibody dilution ratio for Kim‐1‐TRFIA are 1 μg/ml and 1:140, respectively. The linear range is 42.71–4666.69 pg/ml. The intra‐ and inter‐assay coefficients of variation are <10%. The specificity of our Kim‐1‐TRFIA is acceptable. The recovery is between 95.14% and 102.84%. The concentration of Kim‐1 in the serum of patients with AKI is 126.50 ± 67.99 pg/ml, which is significantly higher than that in the serum of healthy controls (49.72 ± 16.40 pg/ml, p <  0.001). Staging patients with AKI by glomerular filtration rate shows that the serum concentration of Kim‐1 increases significantly with increasing disease severity ( p <  0.05). Conclusion A highly sensitive Kim‐1‐TRFIA was established. With this immunoassay, a good differential diagnosis can be made, and healthy people and AKI patients can be differentiated by detecting the concentration of Kim‐1 in the serum. Moreover, the severity of AKI patients can be determined.