Dr. Marla Shapiro: Study takes new look at link between fasting and lipid testing
Published Tuesday, November 13, 2012 8:17AM EST
Last Updated Tuesday, November 13, 2012 8:26AM EST
We often tell patients that they should be fasting some 12 - 14 hours before they do a lipid panel. This panel which measures cholesterol levels and triglycerides is an important indicator for heart disease. However, often a patient will come in having eaten and not do their lab work which means a missed opportunity to do an important screening test. But does it really matter if you fast or not?
This week in the Archives of Internal Medicine is an article looking at exactly this question.
The authors found that fasting prior to blood lipid tests appears to have limited association with lipid subclass levels, suggesting that fasting for routine lipid level determinations may be unnecessary. Those lipid subclasses include the HDL-- the so-called good cholesterol, LDL -- the so-called bad cholesterol, total cholesterol, the ratio and triglycerides.
Although current guidelines recommend measuring lipid levels in a fasting state, recent studies suggest that nonfasting lipid profiles change minimally in response to food intake and may be superior to fasting levels in predicting adverse cardiovascular outcomes, according to the Canadian authors of this research paper.
The authors looked at laboratory data, which included fasting duration (in hours) and lipid results over a 6-month period in 2011 of a large community-based cohort. A total of 209,180 participants (111,048 women) were included in the analysis.
In general, the authors found that among average cholesterol levels the average levels of total cholesterol and high-density lipoprotein (HDL) differed little among individuals with various fasting times. Specifically, these levels varied by less than 2 per cent for total cholesterol and HDL cholesterol, less than 10 per cent for calculated low-density lipoprotein (LDL) cholesterol, and by less than 20 per cent for triglycerides.
The authors found that fasting time showed little association with lipid subclass levels in a large community-based group of people -- a finding that suggests that fasting for routine lipid level determinations is largely unnecessary.
In an accompanying editorial from Harvard it is pointed out that we depend on total and HDL cholesterol levels for most of our decision making. The incremental gain in information of a fasting profile is exceedingly small for total and HDL cholesterol values and likely does not offset the logistic impositions placed on our patients, the laboratories and our ability to provide timely counselling to our patients.
As a result it tips the balance toward relying on nonfasting lipid profiles as the preferred practice.