An interactive website for analytical method comparison and bias estimation.

OBJECTIVES: Regulatory standards mandate laboratories to perform studies to ensure accuracy and reliability of their test results. Method comparison and bias estimation are important components of these studies. DESIGN & METHODS: We developed an interactive website for evaluating the relative performance of two analytical methods using R programming language tools. The website can be accessed at https://bahar.shinyapps.io/method_compare/. RESULTS: The site has an easy-to-use interface that allows both copy-pasting and manual entry of data. It also allows selection of a regression model and creation of regression and difference plots. Available regression models include Ordinary Least Squares, Weighted-Ordinary Least Squares, Deming, Weighted-Deming, Passing-Bablok and Passing-Bablok for large datasets. The server processes the data and generates downloadable reports in PDF or HTML format. CONCLUSIONS: Our website provides clinical laboratories a practical way to assess the relative performance of two analytical methods.

The relationship of plasma neuropeptide Y levels with coronary collateral development.

OBJECTIVE: Neuropeptide Y (NPY), a sympathetic cotransmitter, has been shown to promote angiogenesis in in-vitro models. The aim of this study was to evaluate the relationship of plasma NPY levels with coronary collateral vessel development in patients with coronary artery disease. METHODS: The study included 81 patients with at least one coronary stenosis with at least 80% narrowing in coronary angiography. Collateral vessels were graded according to the Rentrop classification. The study patients were divided into two groups, namely patients with well-developed collaterals and patients with poorly developed collaterals. Well-developed collaterals were defined as Rentrop collateral score of at least 2. Plasma levels of NPY, vascular endothelial growth factor, fibroblast growth factor, and noradrenaline were measured using an enzyme-linked immunosorbent assay. RESULTS: Plasma NPY was significantly higher in patients with well-developed collaterals as compared with patients with poorly developed collaterals (P=0.026). In contrast, plasma noradrenaline was significantly lower in patients with well-developed collaterals (P=0.022). There was no statistically significant difference in vascular endothelial growth factor and fibroblast growth factor levels between groups. The NPY level was positively correlated with the presence of diabetes (r=0.528, P<0.001). The extent of coronary artery disease (Gensini score) was significantly higher in patients with well-developed collaterals (P<0.001). After confounding variables were controlled for, the NPY level in patients with well-developed collaterals was significantly higher than those patients with poorly developed collaterals. CONCLUSION: In this study, NPY levels were found to be significantly higher in patients with well-developed coronary collaterals compared with patients with poorly developed collaterals. New studies are needed to show whether this relationship is causal.