A newer method for calculating low-density lipoprotein (LDL) cholesterol is more accurate than the older method that required people fast before blood was drawn, according to a new study published in Circulation
The results mean that screening for LDL cholesterol could become more convenient if routine fasting before cholesterol tests was eliminated. The researchers who created the new method found in 2013 that the old method underestimated LDL cholesterol levels, particularly for patients with high triglycerides.
The new method uses a chart with 180 different factors to more accurately calculate LDL cholesterol for the individual.
“Although the new LDL calculation method is a bit more complex, the beauty is that it can be performed using information that is already collected in the blood sample for the standard lipid profile and automated in the lab’s computer system to give a more accurate result,” Seth Martin, MD, MHS, co-director of the Advanced Lipid Disorders Center and assistant professor of medicine at the Johns Hopkins University School of Medicine, and one of the creators of the new test, said in a statement
. “Since nonfasting samples are now accurate, it’s more convenient for patients because they can come in anytime and don’t need to return for a second appointment if they have eaten.”
The new method is: total cholesterol minus HDL cholesterol minus triglycerides divided by a specific value from the chart. According to the researchers, the new test may be more complicated, but it doesn’t take any longer to provide results and the cost to administer it is the same.
The researchers used information on more than 1.5 million US participants in The Very Large Database of Lipids, which is created and maintained by Johns Hopkins. The study included 959,153 people who fasted and 586,481 people who did not fast and assessed the impact of fasting on the accuracy of the new method of determining LDL cholesterol.
Using the new method, accuracy of the LDL cholesterol test among patients who did not fast was 92% compared with 71% of patients tested with the old method. Both had been compared to the actual measured value of LDL. While fasting always provided more accurate measures for both the new and the old tests, the differences with the newer method were clinically meaningful in the majority of cases.
Some patients may still need to fast. Fasting may still be important for those patients with a high risk of cardiovascular disease if their treatment might change based on LDL cholesterol calculation, those patients with a triglyceride disorder, or those who need to fast for other types of tests.
“Some patients can have sizable changes in triglycerides after eating, and that is what makes the older Friedewald method less accurate for these people because this isn’t taken into account and it exaggerates the underestimation problem of LDL levels,” said Vasanth Sathiyakumar, M.D., a senior resident at Johns Hopkins. “One of the strengths of our analysis is that we don’t look at average responses but rather look at each participant’s personalized levels using 180 different factors to determine a more accurate calculation.”
Sathiyakumar v, Park J, Golozar A, et al. Fasting vs non-fasting and low-density lipoprotein-cholesterol accuracy. Circ
. 2018;137(1):10-19. doi: 10.1161/CIRCULATIONAHA.117.030677
. Published online ahead of print October, 16, 2017.