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-à-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.

Triglycerides

Markedly increased triglycerides (>500 mg/dL) usually indicate a nonfasting patient (i.e., one having consumed any calories within 12-14 hour period prior to specimen collection). If patient is fasting, hypertriglyceridemia is seen in hyperlipoproteinemia types I, IIb, III, IV, and V. Exact classification theoretically requires lipoprotein electrophoresis, but this is not usually necessary to assess a patient’s risk to atherosclerosis. Cholestyramine, corticosteroids, estrogens, ethanol, miconazole (intravenous), oral contraceptives, spironolactone, stress, and high carbohydrate intake are known to increase triglycerides. Decreased serum triglycerides are seen in abetalipoproteinemia, chronic obstructive pulmonary disease, hyperthyroidism, malnutrition, and malabsorption states.

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