Which blood test to order and how to interpret them
When I am caring for a child or young adult who is overweight or obese there are specific lab tests that are appropriate to obtain. In particular, I need to know how many criteria of the Metabolic Syndrome this patient may have, as this correlates with future risks of chronic disease. What criteria determines the Metabolic Syndrome?
-fasting blood glucose > 105
-blood pressure > 135/90
- triglycerides > 150
-HDL <40(male), <35(female)
*waist circumference >40in (male), >35in (female)
A patient with 3 of the 5 above criteria has Metabolic Syndrome. More than 1/3 of Americans satisfy this diagnosis, increasing their risk for diabetes, heart disease, obesity, cancer, and neurodegenerative disease.
Notice that total cholesterol is absent from the above criteria. Remember, 90% of the cholesterol in our blood is produced by the liver; the level is relatively unaffected by dietary intake. Unless you suffer from one of the hereditary forms of hyperlipidemia, cholesterol levels correlate poorly with subsequent risk of heart disease. (50% of patients with myocardial infarction have normal cholesterol and 50% of patients with abnormal cholesterol levels have normal hearts). In fact, barring other lipid abnormalities, studies show that people with higher cholesterol levels live longer with less dementia, Alzheimer’s disease, or neurodegenerative disease. Too many patients are reflexively placed on statins for an elevated cholesterol level. (white males with previous heart disease have been shown to benefit from statins). We need cholesterol for our cell membranes and for our myelin sheaths that allow communication between neurons. This is a topic for future blogs but the over prescription of statins leads to side effects such as fatigue, muscle aches, a loss of libido, and all the symptoms associated with low Vit D. Only the pharmaceutical companies prosper.
Traditionally, HDL has been considered your “good” cholesterol while LDL has denoted your “bad” cholesterol. However this nomenclature, while easy to remember, is not quite accurate as there are particle subsets of both categories that are both good and bad. Healthy fat consumption increases the good subsets of HDL and LDL while sugar consumption increases the bad subsets. Most labs aren't set up to differentiate the particle subsets of HDL and LDL.
LDL type A: large buoyant fluffy; travel through blood vessels harmlessly
LDL type B: small dense; excavates vessel walls leading to inflammation and plaques
HDL 2: large buoyant; anti inflammatory and protective
HDL 3: small dense: inflammatory
Thus if a patient’s LDL is elevated, one way to determine if the elevation is due primarily to the good or bad particle fraction is to examine the triglyceride to HDL ratio. A ratio less than 2.0 is an indicator the LDL level is good; a ratio greater than 3.0 suggests the LDL level is bad and is a predictor of insulin resistance. In my practice for example, it is quite commonplace for an obese patient to have triglyceride levels of 180 and HDL levels of 35, yielding a very unhealthy ratio of > 5.0. These patients need to be monitored closely for all those disease states resultant from the Metabolic Syndrome.
In addition to lipid analysis ( triglycerides, HDL, LDL, and cholesterol) it is prudent to check for pre-diabetes as 37 % of Americans fall into this category. Typically a physician will order a fasting glucose and HGB-A1C. The later test is an average of the patient’s last 3 months of blood glucose. Unfortunately, these tests can miss the pre-diabetic patients because their pancreas is pouring out oodles of insulin to keep these labs in the normal range! A better test to pick up patients who will ultimately show signs of diabetes is the fasting insulin level. The higher this level the harder your pancreas is working to counter what would otherwise be elevated glucose levels. If one looks at insulin levels from from cultures and tribes who have no access to sugar or processed carbohydrates (Maasai, Kitava, Inuit) they are routinely <5.0. The average american’s fasting insulin level is 9.8. My patients who are obese have fasting insulin levels between 20 and 40! (Incidentally, the quoted upper normal ranges for fasting insulin are way too high and should not be considered a target goal) We have become a society dependent on sugar and processed food and we have insulin levels that are orders of magnitude above normal. Hyperinsulinemia is associated with a host of disease states ranging from diabetes to hypertension, obesity, cancer, nonalcoholic fatty liver disease, hyperlipidemia, reflux……
Other lab tests to consider:
-ALT: a liver function test that correlates with fatty liver disease
-CRP: assesses inflammation and cellular damage
-fibrinogen: assesses inflammation and cardiovascular disease
-ferritin: assesses cardiovascular disease
-homocysteine: associated with heart disease and alzheimer’s disease
-Uric acid: correlates with fructose consumption… associated with Metabolic Syndrome (HTN)
-Vitamin D: associated with osteoporosis, heart disease, diabetes, obesity, cancer, immunity….
So next time you are due for blood work ask your physician which labs are appropriate for your current health profile!