Rapid and sensitive detection of L-FABP for prediction and diagnosis of acute kidney injury in critically ill patients by chemiluminescent immunoassay.

BACKGROUND: Acute kidney injury (AKI) was a common clinical complication among critically ill patients in Intensive Care Unit with high morbidity and mortality. Human liver fatty acid-binding protein (L-FABP) as a renal tubular injury biomarker was considered a predictor of AKI; however, high-throughput and sensitive detection methods were still urgently needed. We constructed a sensitive and rapid detection method for detecting L-FABP and for exploring the clinical application of L-FABP as a predictor for AKI. METHODS: We developed an automated detection method of chemiluminescent immunoassay to measure L-FABP and evaluated the analytical performance of the new methodology including analytical selectivity, analytical sensitivity, linear range, the minimum limit of detection (LOD), repeatability, and accuracy. One hundred patients were enrolled in this study to explore the predictive and diagnostic ability for AKI. RESULTS: The chemiluminescent immune-based L-FABP assay had outstanding analytical sensitivity including the detection limit of 0.88 ng/ml, and a wide linear range of 2 ng/ml to 160 ng/ml. It also exhibited excellent repeatability with intra-analysis CVs of 8.73%, 4.72%, and 3.79%, respectively, and the inter-analysis CVs of 13.47%, 7.28%, and 5.94%, respectively. The recovery rate assay exhibited a good accuracy with three L-FABP concentration of 99.76%, 102.27%, and 96.92%, respectively. The reference interval of L-FABP was between 0.88 ng/ml and 5.98 ng/ml. The evaluation of predictive and diagnostic performance showed that higher concentration of L-FABP indicated higher risk of AKI occurrence and disease progression. CONCLUSIONS: The clinical application of rapid and sensitive detection method of L-FABP based on the newly developed chemiluminescent immunoassay could offer benefits for patients. L-FABP was a potentially predictive and diagnostic biomarker for AKI.

Determination of plasma ß-amyloids by rolling circle amplification chemiluminescent immunoassay for noninvasive diagnosis of Alzheimer's disease.

A rolling circle amplification chemiluminescence immunoassay (RCA-CLIA) was developed for precise quantitation of Aß in plasma. Capture antibodies conjugated with magnetic beads and detection antibodies with collateral single-stranded DNA (ssDNA) were bound to Aß42/Aß40 antigens to form a typical double-antibody sandwich structure. The RCA reaction was triggered by the addition of ssDNA, which generated products with a large number of sites for the binding of acridinium ester (AE)-labeled detection probes, thereby realizing the purpose of the amplification. The RCA-CLIA method had higher sensitivity than conventional CLIA without loss of specificity. Under optimum conditions, the linear range of Aß42 and Aß40 detection was 3.9-140 pg/mL and 3.9-180 pg/mL, respectively, with corresponding low detection limits of 1.99 pg/mL and 3.14 pg/mL, respectively. Plasma Aß42 and Aß40 were detected in the blood of 21 AD patients and 22 healthy people, wherein this ratio could significantly distinguish AD patients from healthy individuals with a sensitivity of 90.48% and specificity of 63.64% for a cutoff value of 154. The Aß42/Aß40 ratio of plasma acts as an accurate indicator for AD diagnosis; therefore, detection of plasma Aß using the RCA-CLIA exhibits great potential in noninvasive diagnosis and progressive assessment of AD.