If you have a strong family history of CAD, your main course of action is to vigorously reduce risk factors that you can control, such as smoking, blood pressure, diabetes, obesity, and cholesterol levels. For some genes, indirect tests can be used to determine if there is a mutation. For example, it is much easier and less expensive to measure blood levels of homocysteine than it is to perform genetic testing. Most people with mild elevations of homocysteine respond well to treatment with folate supplements. If a person fails to respond to folate treatment, other causes of elevated homocysteine, such as vitamin B12 or vitamin B6 deficiency, should be tested.
Cholesterol levels are another example.
Regardless of the specific genetic cause of elevated cholesterol, the approach to testing and treatment is the same. Epidemiology and prevention of coronary heart disease in families. Brown, M.S., et al. Regulation of plasma cholesterol by lipoprotein receptors. Inherited disorders of folate transport and metabolism.