Establishment of a YKL-40 time-resolved Immunoassay and Application in Diabetic Kidney Disease.

To develop a highly sensitive, wide-linear-range time-resolved fluorescence immunoassay (TRFIA) to detect serum YKL-40 and to measure its concentrations in patients with diabetic kidney disease (DKD). A double-antibody sandwich method was employed to establish the YKL-40 TRFIA, which utilizes two antibodies targeting distinct epitopes on the YKL-40 antigen (a coating antibody and a labeled antibody). The assay's linearity, sensitivity, accuracy, specificity, and recovery rate were evaluated. Serum YKL-40 concentrations were measured in healthy individuals and patients with DKD using this TRFIA. The YKL-40 TRFIA exhibited a linear range of 0.5-2000 ng/mL. Intra-assay and inter-assay coefficients of variation were 3.54-9.71% and 4.79-11.27%, respectively. The recovery rate was 101.73-102.62%. The assay showed no cross-reactivity with YKL-39, galectin-3 or CXCL9 and no serum interference. The YKL-40 TRFIA results were highly consistent with those of ELISA (P < 0.0001). The serum YKL-40 level in DKD patients was 314.78 (184.12, 482.49) ng/mL, significantly higher than that in healthy controls [65.73 (48.71, 98.70) ng/mL; P < 0.001]. This study successfully developed a highly sensitive and wide-linear-range method for YKL-40 detection, which can be used for clinical detection.