Prognostic Value of Fasting vs. Non-Fasting Low Density Lipoprotein Cholesterol Levels on Long-Term Mortality: Insight From the National Health and Nutrition Survey III (NHANES-III)
What is the prognostic value of fasting versus nonfasting low-density lipoprotein cholesterol (LDL-C)?
Patients enrolled in the National Health and Nutrition Survey III (NHANES-III) between 1988 and 1994 were stratified based on fasting status (≥8 hours or <8 hours) and followed for a mean of 14.0 (± 0.22) years. Propensity score matching was used to assemble fasting and nonfasting cohorts with similar baseline characteristics. The risk of outcomes as a function of LDL-C and fasting status was assessed using receiver operating characteristic curves and bootstrapping methods. The interaction between fasting status and LDL-C was assessed using Cox proportional hazards modeling. Primary outcome was all-cause mortality, and secondary outcome was cardiovascular mortality. One-to-one matching based on propensity score yielded 4,299 pairs of fasting and nonfasting individuals.
For the primary outcome, fasting LDL-C yielded similar prognostic value as nonfasting LDL-C (C-statistics = 0.59 [95% CI, 0.57-0.61] vs. 0.58 [95% CI, 0.56-0.60; p = 0.73]), and LDL-C by fasting status interaction term in the Cox proportional hazard model was not significant (Pinteraction = 0.11). Similar results were seen for the secondary outcome (fasting vs. nonfasting C-statistics = 0.62 [95% CI, 0.60-0.66] vs. 0.62 [95% CI, 0.60-0.66]; p = 0.96; and Pinteraction = 0.34). Diabetics and persons with a triglyceride >400 mg/dl had a similar prognostic value of fasting and nonfasting LDL levels. Sensitivity analysis using cut-points for fasting of <4 hours versus ≥4 hours or <12 hours versus ≥12 hours showed concordant results with the 8-hour fasting cut-point definition.
The authors concluded that nonfasting LDL-C has similar prognostic value as that of fasting LDL-C. Also, national and international agencies should consider re-evaluating the recommendation that patients fast before obtaining a lipid panel.
The new cholesterol guidelines use total cholesterol (recommended fasting) and major risk factors to calculate the 10-year risk of cardiovascular events. The risk determines the selection of moderate or intense statin dosing to reduce the LDL-C by 35% to 50%, but the guideline avoids the discussion of how long a fast. Since fasting decreases the likelihood that patients will return for follow-up testing and is difficult for afternoon appointments, this study supports using the LDL-C measured nonfasting. The latter can also be used for determining the non–HDL-C and apolipoprotein B for risk assessment and/or treatment targets.
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