Non-fasting LDL-c levels have similar predictive value for mortality as fasting levels

Doran B, Guo Y, Xu J et al.,
Circulation. 2014 Jul 11. pii: CIRCULATIONAHA.114.010001. [Epub ahead of print]

Background

Current guidelines on cholesterol management recommend that lipid panel measurement should be performed after 8-12 hours of fasting [1-3], since certain lipid parameters can be variable depending on the timing and content of the last meal.
Levels of total cholesterol (TC), LDL-c and HDL-c vary little with respect to fasting time, while triglycerides may vary by up to 20-30% [4,5]. It has been suggested that non-fasting lipids may have equivalent predictive value for CV outcomes, since the non-fasting state may more accurately reflect the body’s exposure to circulating lipids [6-8]. No benefit or improved risk prediction has been demonstrated when using non-fasting as opposed to fasting triglycerides [9-12].
This study aimed to evaluate the prognostic value of fasting versus non-fasting LDL-c for prediction of all-cause mortality and CV mortality in men and women, by using the data of 16161 individuals in the National Health Examination and Nutrition Survey III (NHANES-III) database, linked to the National Death Index.

Main results

• 10.023 (62.0%) participants were fasting (>8 hours), and 6238 (38.0%) were non-fasting at the time of phlebotomy.
• In the unmatched cohort, there was an increased risk of all-cause mortality with increasing LDL-C tertile (HR 2^nd vs 1^st tertile: 1.57, 95%CI: 1.34-1.83, HR: 3^rd vs. 1^st: 2.00, 95%CI: 1.70-2.33).
• The C-statistics for fasting vs. non-fasting LDL-c levels for prediction of all-cause mortality were similar (both 0.58), suggesting a similar prognostic value.
• Results were similar when individuals with triglycerides >400 mg/dL were included, or when diabetic patients were considered separately from non-diabetics.
• In a propensity score-matched cohort, a similarly increased risk of all-cause mortality was seen with increasing LDL-c tertile, and no difference in C-statistic was seen between the fasting and non-fasting groups.
• CV mortality was also increased in higher LDL-c tertiles (HR 2^nd vs. 1^st tertile: 1.82, 95%CI: 1.38-2.39, and 3^rd vs. 1^st tertile: HR: 2.94, 95%CI: 2.20-3.93). C-statistics were similar in the fasting and non-fasting groups. Similar findings were seen in the propensity score-matched cohort.

Conclusion

This nationally representative cohort study of data of 16161 individuals, followed for 14.0 years, shows that non-fasting LDL-c have a similar prognostic value as fasting LDL-c levels, for prediction of both all-cause mortality and CV mortality.
These analyses excluded patients with triglycerides >400 mg/dL, but results did not change considerably after including these patients in a sensitivity analysis. Thus, it may not be necessary to use fasting lipid levels to risk stratify patients. The more convenient method of obtaining non-fasting LDL-c levels preserves the prognostic value of the test. These results suggest that the need for fasting LDL-c measurements should be reconsidered by guideline societies.

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