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Original ArticleOpen Access
The Accuracy in Using Modified Friedewald Equation to Calculate LDL from Non-Fast Triglyceride: A Pilot Study
Puavilai W 
,
Laorugpongse D ,
Deerochanawong C ,
Muthapongthavorn N ,
Srilert P
,
Laorugpongse D ,
Deerochanawong C ,
Muthapongthavorn N ,
Srilert P Background: Total cholesterol, HDL (high-density lipoprotein) and LDL (low-density lipoprotein) are
important risk factors of coronary heart disease. It is costly to perform the LDL test for follow-up cardiovascular
diseases (CVD) especially for Gold Card Holders (Thirty Bahts Universal Coverage). Hypertriglyceridemia is
also important as it is associated with uncontrolled type 2 Diabetes mellitus, low HDL, and metabolic syndrome.
Because the serum triglyceride level changes with time after meal consumption, blood test for triglyceride
level should be taken after fasting 12 hours. However, this causes hunger and inconvenience in many patients.
Objective: To find out the optimal time to take blood for triglyceride measurement and using it for calculation
of LDL with the original Friedewald Formula and the new Modified Friedewald Formula.
Material and Method: Patients were asked the approximate time of last meal/eating, drinking soft drink, milk.
Additionally, the time of blood drawn from the patients was recorded. The blood samples were drawn as usual
amounts and the tests were done as the physicians ordered. If enough sera were left, it would be analyzed for
lipid profiles. LDL was also calculated by using standard Friedewald equation (sfLDL) and Modified
Friedewald equation (mfLDL = total cholesterol - HDL - 1/6 triglyceride). Comparison between direct
measured LDL (dmLDL), sfLDL, and mfLDL with time interval of last food, drink intake was done.
Results: There were 999 serum tubes left to be analyzed for lipid profiles and 919 sera (92.0%) left having
triglyceride less than 300mg/dl. Of those, 381, 84, and454 samples came after fasting (nothing per oral =
NPO) approximately less than 8 hours (h), 8-11.9 h, and 12 h or more respectively with sfLDL to dmLDL + 10
mg, comparison of 64.0%, 65.5% and 68.3% respectively. In contrast, comparing mfLDL to dmLDL + 10 mg
being of 82.7%, 83.3% and 84.8% from the same samples and time intervals respectively thus, statistical
significant (p-value < 0.001, odd ratios (OR) 2.59- 2.68). If blood drawn regardless of time from last food
intake with triglyceride less than 300 mg/dl and with the above condition mfLDL, it gave 83.8% related to
dmLDL while sfLDL gave only 66.3% p < 0.0001 and OR = 2.63.
Conclusion: The present pilot study showed 919 of 999 sera (92.0%) with serum triglyceride less than 300 mg/
dl, regardless of the time of the last food intake. The authors used the new Modified Friedewald equation to
calculate that the LDL had 83.8% accuracy when compared to direct measured LDL + 10 mg. This equation
is more accurate than the standard (original) Friedewald equation with OR of 2.63. The authors offer that to
save the cost, the new Modified Friedewald equation should be used to calculate LDL. Then, direct LDL
measurement could be reserved for patients with hypertriglyceridemia, in the treatment of LDL in high-risk
CVD.
Keywords: Blood, Cholesterol, LDL, Triglycerides, Predictive value of tests, Risk factors
important risk factors of coronary heart disease. It is costly to perform the LDL test for follow-up cardiovascular
diseases (CVD) especially for Gold Card Holders (Thirty Bahts Universal Coverage). Hypertriglyceridemia is
also important as it is associated with uncontrolled type 2 Diabetes mellitus, low HDL, and metabolic syndrome.
Because the serum triglyceride level changes with time after meal consumption, blood test for triglyceride
level should be taken after fasting 12 hours. However, this causes hunger and inconvenience in many patients.
Objective: To find out the optimal time to take blood for triglyceride measurement and using it for calculation
of LDL with the original Friedewald Formula and the new Modified Friedewald Formula.
Material and Method: Patients were asked the approximate time of last meal/eating, drinking soft drink, milk.
Additionally, the time of blood drawn from the patients was recorded. The blood samples were drawn as usual
amounts and the tests were done as the physicians ordered. If enough sera were left, it would be analyzed for
lipid profiles. LDL was also calculated by using standard Friedewald equation (sfLDL) and Modified
Friedewald equation (mfLDL = total cholesterol - HDL - 1/6 triglyceride). Comparison between direct
measured LDL (dmLDL), sfLDL, and mfLDL with time interval of last food, drink intake was done.
Results: There were 999 serum tubes left to be analyzed for lipid profiles and 919 sera (92.0%) left having
triglyceride less than 300mg/dl. Of those, 381, 84, and454 samples came after fasting (nothing per oral =
NPO) approximately less than 8 hours (h), 8-11.9 h, and 12 h or more respectively with sfLDL to dmLDL + 10
mg, comparison of 64.0%, 65.5% and 68.3% respectively. In contrast, comparing mfLDL to dmLDL + 10 mg
being of 82.7%, 83.3% and 84.8% from the same samples and time intervals respectively thus, statistical
significant (p-value < 0.001, odd ratios (OR) 2.59- 2.68). If blood drawn regardless of time from last food
intake with triglyceride less than 300 mg/dl and with the above condition mfLDL, it gave 83.8% related to
dmLDL while sfLDL gave only 66.3% p < 0.0001 and OR = 2.63.
Conclusion: The present pilot study showed 919 of 999 sera (92.0%) with serum triglyceride less than 300 mg/
dl, regardless of the time of the last food intake. The authors used the new Modified Friedewald equation to
calculate that the LDL had 83.8% accuracy when compared to direct measured LDL + 10 mg. This equation
is more accurate than the standard (original) Friedewald equation with OR of 2.63. The authors offer that to
save the cost, the new Modified Friedewald equation should be used to calculate LDL. Then, direct LDL
measurement could be reserved for patients with hypertriglyceridemia, in the treatment of LDL in high-risk
CVD.
Keywords: Blood, Cholesterol, LDL, Triglycerides, Predictive value of tests, Risk factors
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