Daniel T Holmes1, Jiri Frohlich, Kevin A Buhr. 1. St. Paul's Hospital Healthy Heart Lipid Clinic and the University of British Columbia Department of Pathology and Laboratory Medicine, Vancouver, BC, Canada. dtholmes@interchange.ubc.ca
Abstract
BACKGROUND: The atherogenic index of plasma (AIP), defined as the base 10 logarithm of the ratio of plasma triglyceride (TG) to high density lipoprotein cholesterol (HDL-C), has been employed as a predictor of cardiovascular risk. We seek to quantify the analytical precision of the AIP using the coefficients of variation (CVs) of the TG and HDL-C assays. METHODS: Error propagation methods are employed to develop a simple formula for the standard deviation of the random analytical error in the AIP assuming that the errors in the TG and HDL-C assays are normally distributed. An alternative derivation assuming log-normal distribution of errors gives nearly identical results while avoiding subtle technical problems. RESULTS: The SD of the AIP is given by sigma(AIP) approximately = 1/ln(10) square root(CV(TG)(2) + CV(HDL-C)(2)) and this formula will provide SD results that are accurate within 0.4% for CVs of TG and HDL-C less than 5%, as compared with results of Monte Carlo simulation. We also explain that the concept of CV cannot be applied to the AIP since it is a logarithm. CONCLUSIONS: The formula provides a simple means to quantify the precision of the AIP from precision data available for the TG or HDL-C assays.
BACKGROUND: The atherogenic index of plasma (AIP), defined as the base 10 logarithm of the ratio of plasma triglyceride (TG) to high density lipoprotein cholesterol (HDL-C), has been employed as a predictor of cardiovascular risk. We seek to quantify the analytical precision of the AIP using the coefficients of variation (CVs) of the TG and HDL-C assays. METHODS: Error propagation methods are employed to develop a simple formula for the standard deviation of the random analytical error in the AIP assuming that the errors in the TG and HDL-C assays are normally distributed. An alternative derivation assuming log-normal distribution of errors gives nearly identical results while avoiding subtle technical problems. RESULTS: The SD of the AIP is given by sigma(AIP) approximately = 1/ln(10) square root(CV(TG)(2) + CV(HDL-C)(2)) and this formula will provide SD results that are accurate within 0.4% for CVs of TG and HDL-C less than 5%, as compared with results of Monte Carlo simulation. We also explain that the concept of CV cannot be applied to the AIP since it is a logarithm. CONCLUSIONS: The formula provides a simple means to quantify the precision of the AIP from precision data available for the TG or HDL-C assays.
Authors: Solomon O Rotimi; David A Ojo; Olusola A Talabi; Elizabeth A Balogun; Oladipo Ademuyiwa Journal: Lipids Health Dis Date: 2012-11-09 Impact factor: 3.876