What is a lipoprotein profile test? This cholesterol test provides information about total cholesterol, LDL-C, HDL-C, and triglycerides.
Traditional lipid profile test is useful for cholesterol diagnosis. But, you should combine advanced testing for an accurate picture of total health.
Lipid profile test, how to use it?
The lipid profile test provides quantities of total cholesterol, LDL-C, HDL-C, and triglycerides.
Lipoprotein profile test measures cholesterol level in the lipoprotein particles (VLDL, LDL, & HDL). Total cholesterol (TS) is the sum of all cholesterol by breaking down lipoprotein particles. Triglycerides number shows triglycerides in all the lipoprotein particles. Triglycerides are most probably from the very low-density lipoproteins (VLDL). Other names for lipoprotein profile test are lipid profile and lipid panel test.
This cholesterol test provides information about
- Total cholesterol,
- Low-density lipoprotein (LDL, so-called bad cholesterol),
- High-density lipoprotein (HDL, so-called good cholesterol), and
- Triglycerides (the most common form of fat in the blood).
TC = LDL-C + HDL-C + VLDL-C
This test estimates total cholesterol, triglycerides and HDL using ultracentrifugation or chemical precipitation.
Total cholesterol is the cholesterol from all lipoprotein particles (VLDL, LDL, and HDL).
Labs measures HDL cholesterol by separating other lipoprotein fractions. High-density lipoprotein cholesterol (HDL-C) quantify cholesterol in HDL particles.
Most labs estimate the concentration of low-density lipoprotein cholesterol using Friedewald formula. This indirect LDL-cholesterol estimation is unreliable when the triglyceride levels are high or low.
Most labs use Friedewald formula to calculate LDL cholesterol.
LDL-C = TC – HDL-C - TG/5
This formula is based on the typical composition of VLDL. This formula is useful only if the triglyceride is within 100 to 400 mg/dl. Otherwise, it will give wrong LDL-C number.
If your triglyceride is below 100, then you can use this formula:
LDL-C (mg/dL) = TC/1.19 + TG/1.9 – HDL/1.1 – 38
LDL-C (mmol/L) = TC/1.19 + TG/0.81 – HDL/1.1 – 0.98.
Ref: The Impact of Low Serum Triglyceride on LDL-Cholesterol Estimation, published in Arch Iranian Med 2008; 11 (3): 318 – 321.
Some labs provide non-HDL cholesterol; calculated from total cholesterol minus HDL-C.
Measurement of cholesterol levels is in mg/dL or mmol/L. There is a flaw in this cholesterol test. It measures just cholesterol in the lipoprotein. This test does not provide the size or number of particles.
Various studies confirm; the small LDLs and large HDLs has a cardiovascular risk. Additionally, high LDL particle and low HDL particle numbers are risks towards heart disease.
But, lipoprotein particle number and size measurement tests are costlier compared with the traditional test. Additionally, it is not available everywhere.
How to make the most of the lipid profile test?
LDL has a close association with heart disease. But, there are two LDL variants. One is large, buoyant not associate with heart disease. Another is small, dense associated with heart disease. High triglyceride level has confirmed risk towards heart disease.
If no access to LDL-P measurement, the next best markers are triglycerides and HDL. High levels of triglyceride indicate the presence of small LDL-P, insulin resistance, and metabolic syndrome.
Certain HDL and triglyceride level indicate the presence of dangerous LDL-B particles; they are:
- High triglyceride levels, i.e. over 120 mg/dL;
- HDL levels of below normal, i.e. 40 mg/dL in men and 50 mg/dL in women;
Low level of triglycerides indicates the presence of harmless LDL-A particles.
Usually, the elevated triglyceride is the result of high VLDL. Lowering triglyceride levels proportionally convert from small, dense LDL into large, fluffy molecules.
Study shows triglyceride/HDL cholesterol ratio of over 3.8 increases the chance for phenotype B.
The triglyceride/HDL-C ratio is a better prediction of the LDL phenotype B. Ref: American Journal of Cardiology Volume 94, Issue 2, pages 219-222, 15 July 2004.
The triglyceride/HDL-C ratio is useless for African-Americans. They do not have high triglycerides; even with severe insulin resistance. These ethnic does not have high triglycerides, even with severe insulin resistance. Because they own a different lipase type (enzymes metabolizing triglyceride expression). Their insulin resistance should assess by glucose abnormalities, obesity, and hypertension. It is not by high triglycerides and or low HDL cholesterol.
LDL-P assessment from lipid profile test
Patient with triglyceride over 130 mg/dl (1.47 mmol/l) indicates high apoB particles (LDL) count.
TG/HDL-C ratio is just predicting the LDL size (not particle concentration LDL-P). But, most patients with small LDLs has increased numbers of LDLs. Ref: DIABETES CARE 2005; 28; 1798-1800.
NonHDL-C is a better marker of cardiovascular risk than LDL-C. NonHDL-C is a better way to correlate with the LDL particle number. Also, it is immediately available from the lipid profile test.
Total cholesterol minus HDL-C gives non-HDL-C; i.e. Non-HDL-C = TC - HDL-C.
Non–HDL-C and ApoB are the best predictors of CHD than the cholesterol it carries. Reference: Circulation 2005; 112: 3375-3383.