From the Guidelines
Total cholesterol is calculated by adding three key components: LDL (low-density lipoprotein) cholesterol, HDL (high-density lipoprotein) cholesterol, and triglycerides, with the formula being Total Cholesterol = LDL + HDL + Triglycerides, but more accurately calculated using the Friedewald formula: Total Cholesterol = LDL + HDL + (Triglycerides/5) or as directly stated in the formula LDL cholesterol = total cholesterol – HDL cholesterol – (0.45 × triglycerides) which can be rearranged to solve for total cholesterol. The calculation of total cholesterol involves understanding the components that make up this value, including LDL, HDL, and triglycerides 1.
- LDL (low-density lipoprotein) cholesterol is often referred to as "bad cholesterol" because it can accumulate in the walls of arteries, leading to plaque formation and increased risk of cardiovascular disease.
- HDL (high-density lipoprotein) cholesterol is considered "good cholesterol" because it helps remove cholesterol from the bloodstream, thereby reducing the risk of cardiovascular disease.
- Triglycerides are another type of fat found in the blood and are included in the calculation of total cholesterol, typically as part of the very-low-density lipoproteins (VLDL) which contain approximately 20% cholesterol. For accurate measurement, it is recommended that blood samples be taken after fasting for 9-12 hours, though non-fasting samples can sometimes be used for total cholesterol and HDL measurements 1. The most recent and highest quality study provides the formula for calculating LDL cholesterol, which can be rearranged to calculate total cholesterol: LDL cholesterol = total cholesterol – HDL cholesterol – (0.45 × triglycerides) 1. This calculation is crucial for assessing cardiovascular risk and guiding treatment decisions, with the understanding that total cholesterol levels are a significant predictor of cardiovascular health 1.
From the FDA Drug Label
The effects of simvastatin on total-C and LDL-C were assessed in controlled clinical studies in adult patients with heterozygous familial and non-familial forms of hyperlipidemia and in mixed hyperlipidemia. simvastatin significantly decreased total-C, LDL-C, and TG, and increased HDL-C
TREATMENT N TOTAL-C LDL-C HDL-C TG* Lower Dose Comparative Study† (Mean % Change at Week 6) Simvastatin 5 mg at night. 109 -19% -26% +10 -12% Simvastatin 10 mg at night 110 -23% -30% +12 -15%
The factors in the total cholesterol calculation are:
- Low-density lipoprotein cholesterol (LDL-C)
- High-density lipoprotein cholesterol (HDL-C)
- Triglycerides (TG) 2
From the Research
Factors in Total Cholesterol Calculation
The total cholesterol calculation includes several factors, which are:
- High-density lipoprotein (HDL)-cholesterol
- Low-density lipoprotein (LDL)-cholesterol
- Triglycerides (TGs) As stated in the study 3, the lipid profile includes total cholesterol, HDL-cholesterol, triglycerides, and LDL-cholesterol.
Lipid Profile Components
The components of the lipid profile are:
- Total cholesterol
- HDL-cholesterol
- Triglycerides
- LDL-cholesterol These components are important in the risk assessment for cardiovascular disease, as mentioned in the study 3.
Calculation of LDL-Cholesterol
LDL-cholesterol can be calculated using the Friedewald equation, which is based on the assumption that the ratio of TG to cholesterol in very-low-density lipoprotein (VLDL) is 5 when measured in mg/dL, as stated in the study 3. However, this equation has limitations, and alternative equations such as the Sampson-National Institutes of Health (NIH) equation 2 and the Martin-Hopkins equation have been derived 3.
Relationship Between Lipid Components
The relationship between lipid components is complex, and different statins have different effects on these components, as shown in the studies 4, 5, 6, and 7. For example, statins can reduce LDL-cholesterol and increase HDL-cholesterol, but the effect on triglycerides and other lipid components can vary depending on the specific statin and dose used.