Lipid reference values in an Irish population

Background and aims: There is limited information on reference values for lipids and lipoproteins in an Irish population. In this observational study, we have described the distributions of lipids in a large Irish cohort. Methods: Over 110,000 lipid profiles were selected from a database of almost 1.5 million consecutive lipid profiles performed in the Clinical Biochemistry Laboratory in University Hospital Galway between 2004 and 2017 to best represent the Irish population. Age- and sex-related reference intervals for both sexes for total cholesterol, triglycerides, HDL cholesterol and LDL cholesterol, from the age of ten to greater than 90 years, were determined. Two methods for estimating LDL cholesterol were also compared. Results: Sex-related differences in lipid distributions arise before the age of 20 years and are life-long. In both sexes total and LDL cholesterol levels gradually increased towards middle age with a decrease towards old age. Levels tended to be higher in males than in females up to mid-life at which stage they cross over with females having on average higher levels. The median of the triglyceride distributions show similar age- and sex-related changes to total cholesterol, but the distributions show a very marked positive skew that is particularly obvious in middle aged males. HDL cholesterol distributions change little throughout life with males having lower levels than females. Changing from the Friedewald formula to that proposed by Martin would impact the management of some patients with dyslipidaemia. Conclusions: This study provides lipid reference values for clinical biochemistry laboratories and clinicians working in Ireland. It is informative for public health initiatives wishing to target dyslipidaemia as a modifiable risk for cardiovascular disease and for investigators researching geographical and temporal variances in lipid parameters.