Dear Dr. Roach: Several years ago, I started going to a new doctor, who said that the way to get the correct cholesterol number is to divide the HDL into the LDL, and if the answer is not 2.5 or lower, I have a problem and should be taking steps to lower it. I am currently interviewing other doctors, as I have stopped going to this doctor for personal reasons. My previous doctor stated that you subtract the HDL from the LDL, and if it is below 100, it鈥檚 OK. Which is correct? I am 68 years old now and in very good health. I was told by a doctor I met while visiting another state that he鈥檇 never heard of the 鈥�2.5鈥� solution.
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T.
There are four main cholesterol numbers acquired from a routine blood test: total cholesterol, HDL cholesterol, LDL cholesterol and triglycerides.
It鈥檚 hard to comprehend four numbers all at once, so you have mentioned two approaches to evaluate the cholesterol picture in a single number.
The first is the HDL:LDL ratio.
Some authorities have described this number as the single best predictor of heart disease (from the standpoint of blood cholesterol levels).
The higher the ratio, the higher the risk. A ratio of 2.5 is extremely good, with a very low risk of heart disease. A ratio of 3.5 or lower is generally considered desirable: At that level, the risk for heart disease is about half the average (the average ratio is 5). A ratio of 9.6 is associated with double the average risk.
The second is the non-HDL cholesterol, which is what you get when you subtract HDL from total cholesterol. This also has met with considerable acceptance, and a number below 100 is considered in the desirable range.
Personally, I think that since HDL cholesterol has independent predictive ability on the likelihood of coronary disease from both LDL and total cholesterol, I use both absolute numbers. I think both the ratio and non-HDL cholesterol are useful, but don鈥檛 tell the whole story.
Remember that cholesterol is only a part of the story for heart disease risk. Smoking and blood pressure are at least as important.
Family history is, too, and often is underappreciated. Diet, exercise and stress management are very important, and most of us physicians don鈥檛 pay enough attention to these.
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Dear Dr. Roach: I have been experiencing shortness of breath whenever I vacation and walk in the mountains. I was a smoker, but I quit 31 years ago. My doctor has sent me for the lung capacity breathing test, and I passed with flying colours. The technician stated that my number was one of the highest she has seen. Can you shed some light on why this is happening, as it concerns me?
N.L.
I have two concerns. The first is that lung capacity is a measure of just what it sounds like 鈥� how big the lungs are.
When the technician says it鈥檚 among the biggest she鈥檚 seen, I worry that it鈥檚 too big. An elevated lung capacity can go along with emphysema, which can be related to distant smoking or can be due to a condition called alpha-1 antitrypsin deficiency.
Emphysema can be diagnosed by other components of pulmonary function tests, particularly a test called the DLCO, and confirmed by X-ray or CT.
However, breathing problems also might indicate heart problems and anemia, so you might need another visit. On the other hand, there is less oxygen in the thin mountain air, so some degree of shortness of breath might not be abnormal.
Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to [email protected].
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