Description
This article is from the Interpretation Of
Lab Test Profiles, by Ed Uthman uthman@neosoft.com with
numerous contributions by others.
31 ASSESSMENT OF ATHEROSCLEROSIS RISK: Triglycerides, Cholesterol, HDL Cholesterol, LDL Cholesterol, Chol/HDL ratio
All of these studies find greatest utility in assessing the risk of
atherosclerosis in the patient. Increased risks based on lipid studies
are independent of other risk factors, such as cigarette smoking.
Total cholesterol has been found to correlate with total and
cardiovascular mortality in the 30-50 year age group. Cardiovascular
mortality increases 9% for each 10 mg/dL increase in total cholesterol
over the baseline value of 180 mg/dL. Approximately 80% of the adult
male population has values greater than this, so the use of the median
95% of the population to establish a normal range (as is traditional in
lab medicine in general) has no utility for this test. Excess mortality
has been shown not to correlate with cholesterol levels in the >50
years age group, probably because of the depressive effects on
cholesterol levels expressed by various chronic diseases to which older
individuals are prone.
HDL-cholesterol is "good" cholesterol, in that risk of cardiovascular
disease decreases with increase of HDL. One way to assess risk is to
use the total cholesterol/HDL-cholesterol ratio, with lower values
indicating lower risk. The following chart has been developed from
ideas advanced by Castelli and Levitas, Current Prescribing, June,
1977. It should be taken with a large grain of salt substitute:
Total cholesterol (mg/dL)
150 185 200 210 220 225 244 260 300
------------------------------------------------------
25 | #### 1.34 1.50 1.60 1.80 2.00 3.00 4.00 6.00
30 | #### 1.22 1.37 1.46 1.64 1.82 2.73 3.64 5.46
35 | #### 1.00 1.12 1.19 1.34 1.49 2.24 2.98 4.47
HDL-chol 40 | #### 0.82 0.92 0.98 1.10 1.22 1.83 2.44 3.66
(mg/dL) 45 | #### 0.67 0.75 0.80 0.90 1.00 1.50 2.00 3.00
50 | #### 0.55 0.62 0.66 0.74 0.82 1.23 1.64 2.46
55 | #### 0.45 0.50 0.54 0.60 0.67 1.01 1.34 2.01
60 | #### 0.37 0.41 0.44 0.50 0.55 0.83 1.10 1.65
65 | #### 0.30 0.34 0.36 0.41 0.45 0.68 0.90 1.35
over 70 | #### #### #### #### #### #### #### #### ####
The numbers with two-decimal format represent the relative risk of
atherosclerosis vis-a-vis the general population. Cells marked "####"
indicate very low risk or undefined risk situations. Some authors have
warned against putting too much emphasis on the total-chol/HDL-chol
ratio at the expense of the total cholesterol level.
Readers outside the US may find the following version of the table more
useful. This uses SI units for total and HDL cholesterol:
Total cholesterol (mmol/L)
3.9 4.8 5.2 5.4 5.7 5.8 6.3 6.7 7.8
------------------------------------------------------
0.65 | #### 1.34 1.50 1.60 1.80 2.00 3.00 4.00 6.00
0.78 | #### 1.22 1.37 1.46 1.64 1.82 2.73 3.64 5.46
0.91 | #### 1.00 1.12 1.19 1.34 1.49 2.24 2.98 4.47
HDL-chol 1.04 | #### 0.82 0.92 0.98 1.10 1.22 1.83 2.44 3.66
(mmol/L) 1.16 | #### 0.67 0.75 0.80 0.90 1.00 1.50 2.00 3.00
1.30 | #### 0.55 0.62 0.66 0.74 0.82 1.23 1.64 2.46
1.42 | #### 0.45 0.50 0.54 0.60 0.67 1.01 1.34 2.01
1.55 | #### 0.37 0.41 0.44 0.50 0.55 0.83 1.10 1.65
1.68 | #### 0.30 0.34 0.36 0.41 0.45 0.68 0.90 1.35
over 1.81 | #### #### #### #### #### #### #### #### ####
Triglyceride level is risk factor independent of the cholesterol
levels. Triglycerides are important as risk factors only if they are
not part of the chylomicron fraction. To make this determination in a
hypertriglyceridemic patient, it is necessary to either perform
lipoprotein electrophoresis or visually examine an overnight-
refrigerated serum sample for the presence of a chylomicron layer. The
use of lipoprotein electrophoresis for routine assessment of
atherosclerosis risk is probably overkill in terms of expense to the
patient.
LDL-cholesterol (the amount of cholesterol associated with low-density,
or beta, lipoprotein) is not an independently measured parameter but is
mathematically derived from the parameters detailed above. Some risk-
reduction programs use LDL-cholesterol as the primary target parameter
for monitoring the success of the program.
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