Development and Evaluation of Up-Converting Phosphor Technology-Based Lateral Flow Assay for Quantitative Detection of NT-proBNP in Blood

Figures

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  Fig 1. Configuration of the up-converting phosphor technology-based lateral flow strip. (a) The excitation and emission spectrum peaks of UCP were 980 nm and 541.5 nm, respectively. (b) The membrane of the UPT-LF strip consists of a test line (T line) and control line (C line), which have been coated with anti-human NT-proBNP monoclonal antibody and goat anti-mouse IgG respectively. The UCP particles were conjugated covalently with the other anti-human NT-proBNP antibody as a reporter. (c) For sample containing NT-proBNP, UCP reporters were captured on both the T line and C line, while they were only captured on the C line for sample without NT-proBNP. The signal from the UCP reporters indicated the strength of the immune reaction.

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  Fig 2. Linearity and sensitivity of the UPT-LF assay. (a) The linear scope of NT-proBNP detected by the UPT-LF assay reached 50–35000 ng/L. (b) Bland–Altman plots for linearity of the UPT-LF assay, the dotted lines represent the confidence interval for 95% limits of agreement. (c) The coefficient of variation values for different concentrations of NT-proBNP above clinical diagnostic cutoff (150 ng/L) were all less than 15%.

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  Fig 3. Stability of the UPT-LF assay. The coefficient of variation for the detection results of the UPT-LF assay and the Roche Elecsys assay were all less than 10% under different sample storage conditions (a), and the bias between the two methods (b) were -0.8%, demonstrating the good stability and reproducibility of UPT-LF assay as Roche Elecsys assay. The significant correlation between the values derived form the EDTA-K2- and 40 heparin-anticoagulated plasma specimens (c) and the bias of 3.84% (d) proved that UPT-LF assay were scarcely affected by anticoagulants. the dotted lines represent the 95% limits of agreement.

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  Fig 4. Correlation between the UPT-LF and the Roche Elecsys assay. EDTA-K2 (a) and heparin (c) anticoagulated plasma and serum samples (e) were used to compare the UPT-LF assay and the Roche Elecsys assay, and Bland–Altman plots for these results are also presented (b, d, f), respectively.

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  Fig 5. Correlation analysis of three types of samples on the UPT system. Correlation analysis between serum and plasma (a), whole blood and serum (c), whole blood and plasma (e) using the UPT system, and Bland–Altman plots for these results (b, d, f) are presented.

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  Fig 6. Distribution of blood plasma NT-proBNP (with EDTA-K2 anticoagulant) in healthy individuals is influenced by both age and sex. The regression formula in females: Y = 2.96X−92.35 (R2 = 0.805, p = 0.001, N = 100); males: Y = 0.76X-10.08 (R2 = 0.302, p = 0.001, N = 100); total: Y = 1.62X−32.37 (R2 = 0.496, p = 0.001, N = 200).