V. BLOOD TESTS
B. Blood LDL Cholesterol Levels
Determination of LDL cholesterol is not done routinely, because it is a difficult, time-consuming, and expen¬sive technique. It must be done fasting because it is calculated by a formula that requires a triglyceride blood level, which must be done after fasting 12 hours. The formula for calculating the blood LDL cholesterol level is as follows:
LDL cholesterol = total cholesterol — HDL cholesterol
— (triglyceride divided by 5) = mg=dl; for the value in mmol=L divide by 2
This formula does not apply if the triglycerides exceed 250 mg/dl.
In individuals age 15–75 optimal LDL cholesterol levels are less than 115 mg/dl (3 mmol/L). In North America, the UK, and Europe the vast majority of individuals have an LDL cholesterol in the range of 130–200 mg/dl (3.4–5.2 mmol/L). In patients with coronary heart disease, the level of LDL is of paramount importance and should be maintained at less than 100 mg/dl (2.6 mmol).
C. HDL Cholesterol Blood Level
Blood testing for HDL cholesterol levels can be done in the nonfasting state. Levels less than 35 mg/dl (0.9 mmol/L) are considered low and less than 27 mg/dl (0.7 mmol/L) is considered unacceptably low. Levels greater than 54 mg/dl (1.4 mmol/L) are considered optimal.