Your cholesterol test is back and your number is normal: under 200.  Breathing easier? Not so fast. You still might be at risk for clogged blood vessels and heart attack.

Researchers have identified at least 17 types of cholesterol -- seven kinds   of "bad cholesterol" -- and are starting to clarify which are most dangerous. At the same time, new tests better pinpoint which types you have.

As a result, some patients with normal readings on standard cholesterol   tests might have elevated risk of heart disease if they have high levels of the   more damaging kinds, doctors say. They can start taking cholesterol- lowering drugs.

Bottom line: Knowing your total cholesterol number isn't enough.

"The cholesterol number that everyone talks about on TV and at parties   isn't that helpful, really," said Boca Raton cardiologist Seth Baum. "It doesn't tell you anything about the cholesterol you have."

Even those who know their "bad cholesterol" number (measuring low-density lipoprotein, or LDL) and "good cholesterol" number (high-density lipoprotein,  or HDL) may not have a full picture. Some researchers say normal LDL and HDL numbers may mask those needing treatment.

"Those are not always very accurate either," said Dr. Jere Segrest, director  of atherosclerosis research at the University of Alabama at Birmingham.  "More people probably need to be taking medication."

Scientists agree that the latest research better explains how and why high cholesterol is a risk, which is crucial in a nation where one in three people have cholesterol levels above 200, borderline for risk. At least 42 million   have levels over 240, putting them at high risk, according to the U.S.  Centers for Disease Control and Prevention.

Research in recent years has clearly linked fat-laden cholesterol with buildup of plaque in blood vessels, which can narrow, block blood flow and trigger heart attacks. Since 1994, studies have shown statin drugs such as Lipitor and Zocor lower cholesterol and prevent heart attacks. Statins now are the nation's top-selling medicine with $15.9 billion in sales and 144 million prescriptions as of last year, according to IMS, a pharmaceutical tracking company.

But half of heart attack victims have normal cholesterol levels, suggesting   to some experts that there's more to know about its link to heart disease. The bad kind, LDL, has at least seven varieties ranging from large particles   of fluffy fat to small particles of dense fat. All are harmful, but small, dense LDL are proving to be the worst.

A study reported in the American Journal of Cardiology found that people with small dense particles were 3 to 4.5 times more likely to have heart disease and 6.9 times more likely to have heart attacks than those with normal numbers. Segrest said small particles may stick to artery walls more easily, starting blockages.

HDL has five varieties, considered helpful because they carry bad   cholesterol from the blood to be destroyed in the liver. Some studies show the largest and fluffiest varieties of HDL are most protective.

Segrest and others say people with normal LDL and HDL numbers may be at risk, if they have high amounts of small, dense types. A cholesterol blood  test called VAP -- Vertical Auto Profile -- can break down a person's cholesterol.

"It would be worth doing once as a baseline to know where you stand," said Segrest, a paid consultant for the test's maker, Atherotech. "I'm not sure   it's worth the money to test everyone. But people may benefit from  knowing."

Other doctors, including Baum, think the number of cholesterol particles is  the key, not the size. The more particles, the more damage to linings of arteries.

"We've had people who have changed [treatment] completely after seeing this," said Baum, who has been paid to lecture on behalf of a competing    test maker, LipoScience.

The new tests are catching on and growing, now given to more than two million people a year, mainly those at high risk.

Some scientists are not convinced that the new approaches are necessary  or better than LDL or HDL numbers. The evidence is strong but "not ironclad" that analyzing cholesterol particle size and counts improves detection and treatment, said Dr. Scott Grundy, who chairs the National Institutes of  Health panel that set the country's cholesterol guidelines.

Grundy said he uses the more specialized cholesterol tests for patients at high risk or with family history of heart disease, and has detected patients not known to have high cholesterol. But it's probably too early to use specialized tests to screen the general public, said Grundy, a University of Texas nutrition expert who has written position papers on cholesterol for    the American Heart Association and the American College of Cardiology.

"We're not sure how to use those numbers yet. It's not so simple," Grundy said.

Also, some fear that doctors may lean too much on the more-detailed cholesterol tests and overprescribe statin drugs, which can cause liver damage in some patients. Plus, the detailed tests cost $90 to $160, compared to a basic test costing $15 to $50.

"These new technologies are potentially important," said Dr. Ronald B. Goldberg, director of lipid disorders at University of Miami Diabetes Research Institute. "But to this point, there is no clear evidence this information is  more accurate in identifying risk for heart disease."

For now, Grundy said patients can follow NIH cholesterol guidelines: LDL below 70 for high-risk people with past heart trouble or many risk factors, below 100 for moderate-risk people with two or more risk factors, and below 160 for low-risk people.

For HDL, keep levels above 40, and 60 is better. Exercise, eat healthy, quit smoking and lose weight if needed.