Medical Tests

What will happen during laboratory sleep testing?

DEAR DOCTOR K: My doctor thinks I may have sleep apnea, and he wants me to go to a sleep lab to be tested. What will happen during the testing?

DEAR READER: Sleep apnea is a serious health condition in which breathing stops or becomes shallower. In the most common form, obstructive sleep apnea, the tongue or throat tissues temporarily and repeatedly block the flow of air in and out of your lungs. This can happen hundreds of times each night. Laboratory sleep tests are the most reliable way to diagnose this problem.

Should I get a c-reactive protein test to check for heart disease?

DEAR DOCTOR K: Both my parents had heart disease, so I'm worried I might get it. A friend said I should get a CRP test, but my doctor hasn't ordered one. Should I ask him about the test?

DEAR READER: The answer is controversial. For full transparency, I should say that this test was developed and studied by a colleague of mine at Harvard Medical School, and revenue from the test comes to my colleague and to the hospital where I practice.

What are the risks and benefits of mammograms?

DEAR READERS: In yesterday's column, I answered a question from a 47-year-old woman who had never had a mammogram and wondered if she should have one. She had heard that one group of experts -- the American Cancer Society (ACS) -- had recently changed its recommendations on this issue.

When should I start getting mammograms?

DEAR DOCTOR K: I'm a 47-year-old woman who has never had a mammogram. Some experts recommend I get one, but others do not. I understand that the American Cancer Society recently updated its recommendations about breast cancer screening. Does it say I should have a mammogram? If so, which experts should I believe?

DEAR READER: I'm surprised when people are bothered by medical experts having different opinions. Expert politicians, expert lawyers, expert architects -- experts of all kinds disagree with each other all the time. Why? Because it is rare for the "truth" of any question to be clear beyond dispute.

What will happen during my pulmonary function tests?

DEAR DOCTOR K: My doctor ordered breathing tests to see if I have asthma. He didn't tell me what it's like to go through this. Can you explain?

DEAR READER: The tests your doctor almost surely is referring to are pulmonary function tests. The tests are painless. You breathe in and out through a tube that is connected to various machines.

Should I have my vitamin D level checked?

DEAR DOCTOR K: I've read several articles about the negative effects of a low blood level of vitamin D, but my doctor said I didn't need to have my level checked. Why not?

DEAR READER: Many of my patients are asking me the same question. Vitamin D has been in the news a lot in recent years, but we still don't have solid answers to many questions, including yours. There is strong evidence that people with a low blood level of vitamin D have higher rates of osteoporosis (thin bones).

Is the home-screening test for colon cancer effective?

DEAR DOCTOR K: I heard about a new home test that detects colon cancer. Is it a good alternative to colonoscopy?

DEAR READER: The new test appears to be an advance, but I don't think it's as good as colonoscopy. Particularly for people who are at higher risk for colon cancer, I regard colonoscopy as the best test. Colon (or colorectal) cancer lies in the wall of the colon. It can cause painless bleeding. The amount of blood can be so small ("occult blood") that it isn't visible in the bowel movement, but it can be detected by chemical tests.

Should I request advanced cholesterol testing?

DEAR DOCTOR K: Should I request "advanced" cholesterol testing at my next checkup?

DEAR READER: A standard cholesterol test, or lipid profile, measures levels of HDL, LDL, total cholesterol and triglycerides in the blood. So-called "advanced" cholesterol testing is a more detailed version of this test. Cholesterol is a waxy, yellowish fat. It travels through your bloodstream in tiny, protein-covered particles called lipoproteins. These particles contain cholesterol and triglycerides, a type of fat.

Why would a doctor order an ultrasound of the carotid artery?

DEAR DOCTOR K: My father's doctor wants him to have an ultrasound of his carotid artery. What is the carotid artery? What will the doctor be looking for?

DEAR READER: The carotid arteries carry oxygen- and nutrient-rich blood from the heart to the brain. These crucial arteries can become narrowed by the cholesterol-filled plaques of atherosclerosis. Blood clots can form from the plaques, then break off and travel to the brain. There, they can lodge in small arteries, interrupting the vital flow of blood to brain cells.

Will studies of our genes change medicine and improve our lives?

In yesterday's column, a reader asked whether she should be tested for genes linked to Alzheimer's disease. Today, I thought I'd give you my view on the larger question: Will studies of our genes change the practice of medicine and improve our lives?

My answer: During my career, progress in human genetics has been greater than virtually anyone imagined. However, human genetics also has turned out to be much more complicated than people imagined. As a result, we have not moved as rapidly as we had hoped in changing medical practice.