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Assessing Cardiovascular Risk with a Blood Test: What Do All Those Numbers Mean?
1/7/2008
In a previous feature article, I explained why I screen children at higher-than normal cardiovascular risk. Now I’d like to take a closer look at these blood tests to help you understand the significance of all those numbers on that laboratory results page. Of course, I expect that someone in your pediatrician’s office will review the results with you as well.
The basic screening tool for cardiovascular risk is a fasting blood test. The child being tested must not have eaten for 12 hours to get an accurate measurement of blood sugar, triglycerides, and certain other markers. If you make this appointment for early morning and bring a snack for after the blood draw, everyone involved will be happier!
The American Academy of Pediatrics recommends a complete blood count (CBC) and lipid screening for kids who have such cardiovascular risk factors as a family history of premature heart disease or a parent with high cholesterol. Using the same blood sample, the Dr D cardio screening for high-risk kids also looks at other blood components associated with cardiovascular problems. These additional results can tell us the size and density of cholesterol, influences on clotting, and the degree of systemic inflammation in the child being tested.
What I Screen, and Why
I’ve already explained the complete blood count (CBC) in another feature, but here are some brief explanations of the other blood factors I consider in determining cardiovascular risk for a child or adolescent:
Lipid Profile. The test measures levels of total cholesterol, low-density lipoprotein (LDL, or “bad” cholesterol), high-density lipoprotein (HDL, or “healthy” cholesterol), and triglycerides (a combination of fat and sugar). These are all important markers for assessing cardiovascular risk. These levels are determined by heredity, nutrition, weight, degree of physical activity, gender, alcohol intake, and stress level. In general, the higher your HDL level and the lower your levels of LDL and triglycerides, the better. Ideally total cholesterol should be under 170 mg/dL, and LDL cholesterol under 110 mg/dL.
What you should know about cholesterol
Cholesterol is necessary for healthy function. The liver makes nearly all the cholesterol we need, so the cholesterol in food is mostly surplus to our needs, and ends up stored as fat. LDL carries cholesterol to the cells, and HDL trucks the excess back for disposal. That’s why you want high levels of HDL “trucks.”
C-reactive Protein. C-reactive protein (CRP) is a marker for systemic inflammation, now believed to be an important factor in the laying down of fatty plaque in the blood vessels. In general, a CRP score of less than 1.0 mg/L indicates low risk for cardiovascular disease. These scores can be influenced by other sources of inflammation, and may be skewed, for instance, if your child has an infection when the test is done.
Lipoprotein a, or Lp(a). High levels of this special form of LDL are associated with an increased risk for heart attack and stroke. The desirable level for adult is less than 30 mg/dL
Apolipoprotein A1 (Apo A1) and B (ApoB). These are protein coatings on HDL (Apo A1) and LDL (Apo B). Some researchers think levels of these two markers provide a better picture of cardiovascular risk than the usual cholesterol levels. In adults, cardiovascular risk would be lower if Apo A1 was over 123 mg/dL and ApoB was under 100 mg/dL.
Homocysteine (Hcy). Homocysteine is an amino acid linked to early development of heart and blood vessel disease. It’s also a marker for low levels of vitamins B-6, B-12 and folate. Your child can get more of these B vitamins by eating plenty of leafy green vegetables and fortified grain products, but high homocysteine levels generally call for prescribed supplementation of vitamins B-12 and folate to lower homocysteine levels to healthier levels (optimally under 6 micomol/dL).
Fibrinogen. Fibrinogen enourages blood clotting. Ideal levels are less than 300 mg/dL.
