Why do you Order Triglycerides?
abstract & commentary
Synopsis: The serum triglyceride measurement does not provide meaningful information about coronary heart disease risk in men.
Source: Avins AL, Neuhaus JM. Arch Intern Med 2000;160: 1937-1944.
The objective of this study was to determine the value of measuring triglyceride levels in addition to measuring cholesterol and its subfractions. Prior research had shown that triglycerides were useful in predicting coronary heart disease (CHD).
Avins and Neuhaus performed a secondary analysis of data from the Multiple Risk Factor Intervention Trial, the Lipid Research Clinics Coronary Prevention Trial (LRC-CPPT), and the Lipid Research Clinics Prevalence and Mortality Follow-Up Study. The other variables studied were total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and age, fasting blood glucose, blood pressure, cigarette smoking, body mass index, and post-menopausal estrogen use.
In men, categorical analyses using both triglyceride and cholesterol levels were similar to using cholesterol categories alone. In women, however, at least one study showed that women with both a high cholesterol level and a high triglyceride level were more likely to have a coronary event.
Comment by Ralph R. Hall, MD, FACP
As is pointed out in the editorial by Rubins,l the debate about triglycerides as a risk factor predictor has gone on for years. This article will not stop this debate.
We all remember the Helsinki Heart Study2 in which the decreased mortality with treatment occurred primarily in patients who had high triglycerides. The fibrates have not worked well in patients with a high LDL/HDL ratio unless there was also a high triglyceride level. Therefore, even though the triglycerides do not predict CHD better than cholesterol fractions, they may help to determine therapy.
In addition, patients with extremely high triglycerides were excluded from one of the studies analyzed (LRC-CPPT). This may affect the results of the study. Rubins points out in the editorial that European studies show a correlation between elevated triglycerides and CHD while this study carried out on an American population did not. Therefore, population characteristics may be a factor in these results. Further, Pedano and colleagues3 have demonstrated that in patients with types IIb and IV hyperlipoproteinemia, the triglycerides are associated with a prothrombotic state with hypercoaguability and a low fibrinolytic activity.
Avins and Neuhaus note in their study that the LDL/HDL ratio is more predictive of risk than triglycerides. However, we are left with the fact that the laboratory uses the triglyceride level to calculate the low-density lipoprotein cholesterol (LDL-C) level because the direct measurement for LDL-C is more difficult to do. So, even if you do not order the triglycerides the lab will have tested for triglycerides. What are we clinicians to do?
References
1. Rubins HB. Arch Intern Med 2000;160:1904-1905.
2. Manninen V, et al. Circulation 1992;85:37-45.
3. Pedano J, et al. Metab 2000;49:942-949.
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