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Making sense of cholesterol tests

Time to get your cholesterol checked. Okay, but which test should you get? It’s not so simple anymore. Here is a rundown of some of the choices and their pros and cons:

Total cholesterol. This is the simplest and least expensive test, and fasting isn't necessary. The test doesn’t require any sophisticated lab work, either. The simple, do-it-yourself home cholesterol tests measure total cholesterol. A reading of 200* or below puts you in the desirable category; 200–239 is borderline high; and 240 or more is high.

But total cholesterol includes both “good” high-density lipoprotein (HDL) cholesterol, and the “bad” varieties, chiefly low-density lipoprotein (LDL) and very-low-density lipoprotein (VLDL). So if your total cholesterol is in the desirable category, it’s possible that you may have unhealthy levels of HDL (too low) and LDL and VLDL (too high). Think of total cholesterol as a first glimpse, a peek. Doctors are not supposed to make any treatment decisions based on this number alone.

Cholesterol levels can be lowered by stress (physical or psychological) or infection. An injury, stroke, or heart attack may have the same effect. Sometimes the first sign of cancer is a dramatically lower cholesterol reading. So if your cholesterol levels are unusually high or low, your doctor will probably want to repeat the test some weeks later. Abnormal readings may also lead to tests for other medical problems.

Total cholesterol and HDL. HDL wins its laurels as the “good” cholesterol because it sponges up cholesterol from blood vessel walls and ferries it to the liver for disposal. In contrast, LDL deposits the harmful fat in vessel walls.

According to 2004 guidelines, an HDL level of 60 or above is protective against heart disease, and below 40 makes you vulnerable to it.

The ratio of total cholesterol-to-HDL is important; the smaller the number the better. For example, someone with a total cholesterol of 200 and an HDL of 60 would have a ratio of 3.3 (200 ÷ 60 = 3.3). If that person’s HDL was low — let’s say 35 —the total cholesterol-to-HDL ratio would be higher: 5.7.

Reports from the Framingham Heart Study suggest that for men, a total cholesterol-to-HDL ratio of 5 signifies average risk for heart disease; 3.4, about half the average risk; and 9.6, about double the average risk. Women tend to have higher HDL levels, so for them, a ratio of 4.4 signifies average risk; 3.3 is about half the average; and 7, about double. If you have a high level of total cholesterol, it may be less alarming if your total-to-HDL ratio is low.

Cholesterol: The good and the bad of it

HDL High-density lipoprotein

  • Makes up 20%–30% of total cholesterol
  • The “good” cholesterol
  • Moves cholesterol from arteries to the liver.

LDL Low-density lipoprotein

  • Makes up 60%–70% of total cholesterol
  • Main form of “bad” cholesterol
  • Causes build up of plaque inside arteries.

VLDL Very-low-density lipoprotein

  • Makes up 10%–15% of total cholesterol
  • With LDL, the main form of “bad” cholesterol
  • A precursor of LDL.

 LDL cholesterol. The LDL measurement is usually considered the most important for assessing risk and deciding on treatment. The definition of a healthy level keeps on getting lower. Current guidelines say an LDL of 100 is “optimal.” In a revision of the guidelines in early 2004, doctors were advised that an LDL of less than 70 should be a “therapeutic option” for very-high-risk patients. Some experts say that would be a healthy LDL goal for all of us.

Your LDL is computed by plugging the measurements for total cholesterol, HDL, and triglycerides into a: LDL = Total cholesterol – HDL – (Triglycerides ÷ 5)

You have to fast for about 12 hours before the test because triglyceride levels can shoot up 20%–30% after a meal, which would throw off the equation. Alcohol also causes a triglyceride surge, so you shouldn’t drink alcohol for 24 hours before a fasting cholesterol test.

Another important limitation: At a triglyceride level of about 250 or higher, the calculation becomes less reliable because dividing triglycerides by a factor of 5 provides a less accurate estimate of VLDL.

The numbers to know

Test

Healthy level

Total cholesterol

under 200 mg/dL

LDL (bad) cholesterol

under 100 mg/dL

HDL (good) cholesterol

over 40 mg/dL

Triglycerides

under 150 mg/dL

C-reactive protein (CRP) is a protein in the blood that increases with inflammation. Because atherosclerosis is fundamentally an inflammatory process, many experts believe that CRP testing could lead to early detection and therefore save lives. The American Heart Association says CRP tests are warranted for people at intermediate risk for heart disease, but not those at the low and high ends of the risk spectrum.

The current guidelines recommend a fasting cholesterol test every five years for everyone beginning at age 20. A fasting cholesterol test gives you the important numbers: total, LDL, and HDL cholesterol, as well as triglyceride levels. If you have difficulty fasting or your triglycerides are over 250, you are a candidate for one of the new tests that measure LDL directly. But unless you’re a special case, sophisticated breakdowns of the various cholesterol types will only give you a case of information overload. Skip them and stick to the basics.

February 2005 Update

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