Significant hypertriglyceridaemia and HDL cholesterol assays

It was good to read the excellent editorial by Preiss and Neely ¹ on the routine reporting of non-HDL cholesterol. However, they overlooked one issue with contemporary HDL cholesterol methods, namely, interference from triglycerides. This is greatest when triglyceride concentrations exceed 11.3 mmol/L (1000 mg/dL), as reported by assay manufacturers, ² and often presents as a patient with significant hypertriglyceridaemia with atypically normal or raised HDL cholesterol. Dilution of HDL cholesterol with saline may be required to obtain accurate measurement of HDL cholesterol concentration. ³ Otherwise, the derived non-HDL cholesterol concentration and total cholesterol/HDL ratio may also be inaccurate in the presence of significant hypertriglyceridaemia.

Diagnostic laboratories can detect this effect of hypertriglyceridaemia by several different means. For example, triglycerides could be measured on all HDL cholesterol requests, or when the lipaemic index ⁴ exceeds a given threshold or by measuring triglycerides when HDL cholesterol is elevated, and so forth. Each of these options has its pros and cons. Improved analytical software can help to identify potential at-risk samples, but it is important that the appropriate dilution is performed to ensure that the resulting triglyceride concentration is <11.3 mmol/L.