ANSWER: There are four main cholesterol numbers acquired from a routine blood test: total cholesterol, HDL cholesterol, LDL cholesterol and triglycerides. It’s 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’t 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’t pay enough attention to these.

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 colors. 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.

ANSWER: I have two concerns. The first is that lung capacity is a measure of just what it sounds like — how big the lungs are. When the technician says it’s among the biggest she’s seen, I worry that it’s 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.

The booklet on COPD explains both emphysema and chronic bronchitis, the two elements of COPD, in detail. Readers can obtain a copy by writing: Dr. Roach Book No. 601, 628 Virginia Dr., Orlando, FL 32803. Enclose a check or money order (no cash) for $4.75 U.S./$6 Can. with the recipient’s printed name and address. Please allow 4-6 weeks for delivery.

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 ToYourGoodHealth@med.cornell.edu or request an order form of available health newsletters at 628 Virginia Dr., Orlando, FL 32803. Health newsletters may be ordered from www.rbmamall.com.