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Requiring patients to fast for 8 to 12 hours before a lipid panel blood draw is common practice, but fasting adds no clinical value and is an unnecessary burden on patients, researchers said.

Analysis of data from the National Health and Nutrition Survey III (NHANES-III) revealed no significant difference between fasting and nonfasting LDL cholesterol levels when it came to predicting all-cause and cardiovascular mortality, New York University associate professor of medicine and colleagues wrote in

The study is not the first to find no benefit for fasting prior to a lipid panel blood draw. published in Archives of Internal Medicine in 2012, failed to show an impact on lipid panel outcomes associated with the practice, and researchers concluded that fasting for routine lipid levels is "largely unnecessary."

Fasting Widely Recommended

Many national and international guidelines for cholesterol management do recommend fasting blood draws, however, including the of the American College of Cardiology and the American Heart Association.

"I think it's time to change this recommendation, which is based on expert consensus without any data to back it up," Bangalore told MedPage Today. "Fasting is inconvenient for the patient, and doing away with it could simplify the process of assessing patient risk."

Bangalore said abandoning the fasting requirement could speed up the process of identifying and treating patients who need to be on statin therapy.

"When we tell them, 'You have to come back at a later date to have your fasting lipid panel checked,' many times patients don't have the time or they don't come back," he said.

He added that fasting could even put diabetic patients at risk for hypoglycemia.

"During a 24-hour period people spend most of their time in a nonfasting state," he said. "When we ask them to fast it is an artificial situation. To me it's like studying for an exam to do well on a test. It is an artificial situation."

Fasting and Nonfasting LDL Similar

Bangalore and colleagues analyzed data derived from 16,161 NHANES-III participants (surveyed between 1988 and 1994), representing more than 172 million adults in the U.S. Participants were excluded from the analysis of LDL cholesterol calculations when data were missing for HDL cholesterol, total cholesterol, or triglyceride levels and when triglyceride levels were 400 mg/dL or more.

Participants were stratified on the basis of fasting status (≥8 or <8 hours) and followed for a mean of 14 (±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 cholesterol and fasting status was assessed using receiver-operating characteristic curves and bootstrapping methods.

The researchers conducted sensitivity analyses at 5, 10, and 15 years of follow-up to ensure that the significance of fasting status did not vary by follow-up length.

They evaluated the association of LDL cholesterol levels with outcomes after adjustment for potential confounders. Participants were stratified by tertiles of LDL cholesterol levels (<100, ≥100-130, and ≥130 mg/dL), with the lowest tertile used as the reference group.

One-to-one matching yielded 4,299 pairs of fasting and nonfasting participants. For the primary outcome, fasting LDL cholesterol yielded prognostic value similar to that for nonfasting LDL cholesterol (C statistic=0.59 [95% CI 0.57-0.61] versus 0.58 [95% CI 0.56-0.60]; P=0.73), and LDL cholesterol by fasting status interaction term in Cox proportional hazards model was not significant (P_interaction=0.11).

Similar results were seen for the secondary outcome (fasting versus nonfasting C statistic=0.62 [95% CI 0.60-0.66] versus 0.62 [95% CI 0.60-0.66]; P=0.96; P_interaction=0.34].

In an unmatched cohort, C-statistics of triglyceride levels in fasting versus nonfasting groups predicting cardiovascular mortality were not significantly different (C-statistics 0.62 [95% CI 0.60-0.64] versus 0.61 [95% CI 0.59-0.64], respectively; P=0.81). The C-statistics for total cholesterol levels for cardiovascular mortality in fasting and nonfasting groups were also similar (C-statistic 0.64 [95% CI 0.62-0.66] versus 0.63 [95% CI 0.60-0.65]; P=0.49).

An important limitation cited by the researchers was the absence of patients who had both fasting and nonfasting blood measures taken at the same time.

'Enough to Change Clinical Practice'

"Our study suggests that a nonfasting LDL cholesterol measurement offers a more convenient method of phlebotomy while preserving the prognostic value of the test," the researchers concluded, adding that the fact that no difference in outcomes were seen for fasting and nonfasting triglycerides and total cholesterol, as well as LDL, should prompt health policymakers to revisit recommendations calling for fasting lipid profiles.

In the absence of new research showing fasting to offer advantages over nonfasting prior to lipid panel blood draws, Bangalore said physicians should not be telling patients to fast.

"This (study) along with a few others that have been published is compelling enough to change clinical practice," he said. "I would say, yes, research is needed, but research is needed only to show that fasting is a better prognostic indicator.... If we want to do what we have been doing, we need research to actually prove that it is more efficacious."

From the American Heart Association:

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