Diagnostic Testing – a Brief Consumer's Guide
Section titled “Diagnostic Testing – a Brief Consumer's Guide”My patient, John, a 50-year-old diabetic, smiled gratefully when I gave him the news. His blood test looked good. We'd just drawn blood and run it through our shiny new government-certified analyzer.
"John," I said, "we just checked your hemoglobin A1c and it is 7.2. This isn't too bad. We like to see it under 7, but this is pretty close and we should have no trouble achieving that goal."
He was happy and I was happy. With the recent purchase of this new machine, we could measure hemoglobin A1c in our office at a fraction of the Seattle laboratory's price. We were already performing a few tests in our office. To increase our scope and our speed of reporting, we purchased the new machine. We were optimistic about the benefits.
Just to make sure, I double-checked John's A1c number (at no cost to him) by sending his sample to our regular Seattle lab. When I received the results, I had to call him back. His hemoglobin A1c was actually 8.2. That's a big difference in what kind of medication adjustment we needed to make. He was unhappy and I was unhappy. After two more patients, two more inaccurate results, our shiny new hemoglobin A1c system was on its way back to the manufacturer, government approval notwithstanding.
Every year, Americans lavish billions of dollars on laboratory tests and other diagnostic studies. Unfortunately, there is no medical Consumer Reports to help you spend your money wisely. This month, we try to fill that gap. We take a look at laboratory testing and diagnostic imaging. Then we recommend a few labs we have found to be reliable.
Testers Must be Tested
Section titled “Testers Must be Tested”These days I resist the ads promising I can buy a miniature version of a clinical laboratory system. There are just too many details required to ensure the thing is putting out correct numbers
Laboratory machines require care and feeding. Technicians don't just run your blood through it and collect the report. They also run test samples for which the levels are known. They need to be sure the machine returns the right answer. Sometimes it does not. Then the technicians have to figure out why and correct the problem. It could be a contaminated part, a chemical reagent that went bad, something wrong with a pump, thermostat, heater, tube, timer, circuit board or detector. Major labs also face continual testing by federal agencies, which send mystery samples and require the lab to correctly identify what they contain. The feds don't insist that all labs participate, but serious labs accept the challenge.
Cholesterol Roller-coaster
Section titled “Cholesterol Roller-coaster”Even with government testing, not all labs produce consistent results. Have you had your cholesterol tested recently? If you were not careful about choosing the laboratory, that cholesterol level could have an error rate of plus or minus 15 percent. If your cholesterol level came out as 200, it could actually be 230 or 170! (see this article from the May 1988 Nutrition Action Healthletter). The ramifications are not insignificant. With a cholesterol reading of 230, your physician might prescribe an expensive statin drug. Do you really need it? You don't know if you can't trust the results.
Nutritional Testing
Section titled “Nutritional Testing”People are always interested in their nutritional status, so a few years ago I set up a protocol using a comprehensive nutritional analysis from a Medicare-certified laboratory in Texas. Their technique would measure about twenty nutrients for $400, a sweet deal considering sometimes it costs that much to measure one nutrient using conventional methods.
I sent in the first sample. The report showed my patient low in folic acid and carnitine. A month later, a sample from the same patient, no change in supplements, came back low in coenzyme Q10, potassium and riboflavin. What?!!? I called the lab. The director explained that the values differed because they can change over time. That sounded fishy to me, but even if the assay was correct, it isn't worth $400 to know that your folic acid is low in January when it will be normal again in March.
Although the dream of getting a complete accurate profile of nutritional status seems impractical, it still makes sense, at times, to test for a single nutrient. If you suffer from osteoporosis, it's likely your vitamin D levels are low and I need to test for that and supplement to bring them up. We use two different labs that do this test, and they both do a pretty good job, say within 5 to 7 percent of each other. Given that a low value is around 35 and a high value over 60, that's adequate accuracy.
Diagnostic X-rays
Section titled “Diagnostic X-rays”Originally, all we had was X-ray, images from electromagnetic radiation, so that area of medicine was given the name "Radiology." Today, though, we have several kinds of images derived from radiation, including CT (a three-dimensional X-ray) and radionuclide scans (from radioactive materials injected into the bloodstream) called SPECT and PET scans. We have images that require no radiation, derived from ultrasound and strong magnetic fields (MRI).
Like laboratory tests, these tests have their limitations. I remember a great muscular man, a meat-cutter who consulted me in Milwaukee with severe fatigue. He looked like a football player, but he could barely pick up his fork. He was very anemic and required hospitalization and eventually a series of transfusions. A full work-up including a CT scan found no cause for his severe anemia, and the hematologist said, "It's just one of those things we won't figure out. You'll just have to send him home and hope he needs no more transfusions."
Having attended medical conferences at the Mayo Clinic, I was impressed with their skill at solving tough problems. Against the hematologist's recommendation, I transferred my weak-as-a-kitten butcher to Mayo. They ran a different kind of imaging study and discovered an enlarged spleen the CT scan had missed. The reason the first scan had failed was that the spleen in this man was of equal density with the surrounding tissue (as far as the scanning beam was concerned), and so, like two clouds in the sky of similar shade of grey, blended into the normal background.
Beware of Supermarket Tests
Section titled “Beware of Supermarket Tests”Recently, patients have been asking me about "Lifeline Screening" tests. You can read full details in the December 2001 newsletter. Ultrasound of the carotid arteries produces accurate results only in the hands of highly qualified technicians using the very best equipment. Anyone offering that test in your church or the supermarket parking lot is much less likely to provide accurate information. For a balanced coverage, see this July 2005 Washington Post article.
Testing the Heart to Death
Section titled “Testing the Heart to Death”Years ago, while I was giving a young man a routine physical, I discovered an unusual heart murmur. The man felt fine, and all other physical findings were normal, but just to be sure we did an electrocardiogram. An electrocardiogram, or EKG, measures electrical activity of the heart. That looked basically normal, but showed an unusual wave form. So we did an echocardiogram, in which sound waves are bounced in and out of the heart. Sure enough, nothing was wrong with his valves, but the test was not entirely normal either, so I discussed this with a colleague and then sent him to a cardiologist. The cardiologist agreed his heart was probably normal but, just to be sure, performed a stress test. The stress test was pretty much normal, but not quite, so the cardiologist performed a cardiac catheterization. In this procedure the doctor inserts a tube into an artery or vein in the leg and pushes it up into the chambers of the heart. That test was unequivocally normal.
While most heart tests can be expensive, they carry little risk. Not so cardiac catheterization. It can be fatal; I've seen it happen. This is an extreme example of over-testing, but every doctor has experienced similar situations. Sometimes your doctor will not be too thrilled about a particular test. If she doesn't order a certain test, it is not because she doesn't care about you. If the insurance company bulks at paying for a test, that does not necessarily mean they are cheapskates. The test may be unnecessary or not worth the risk.
The major diagnostic tool is the human mind, properly applied. Diagnostic tests support, but do not replace, this oldest of medical devices. Most importantly, you need to understand what the test involves and decide if a particular medical test will benefit you. Group Health Cooperative provides good, solid descriptions of diagnostic tests.
Our Consumer Best Buys
Section titled “Our Consumer Best Buys”Continuing our Consumer Reports analogy, there are good buys out there. Our favorite lab is Labcorp, located in Seattle. Their quality is tops and their large volume allows them to offer a good price. If you have your cholesterol checked through our Labcorp service here at the clinic, you know your numbers don't vary that much from test to test unless you've begun or discontinued medication. That's because Labcorp far exceeds required standards. Many labs do not. Other laboratories we've found trust-worthy include Meridian Valley Clinical Laboratory and Genova Diagnostics. Not that all others are slip-shod, but these are the ones we think are reliable.
We all want to forestall illness and decay, and wisely chosen laboratory tests can help. That is why we offer "Direct Access" testing. Many people use this service to track their own cholesterol or general health panel.
More Medical Consumer Resources
Section titled “More Medical Consumer Resources”Medicine for People! has long been interested in helping you sort out the useful from the worthless and the good deals from the bad ones. Here are links to previous topics.
Diagnostic tests
"Lifeline Screening"
Cancer Screening
Colon Cancer Screening
Colon Cancer Screening
Mammography
Nutritional Supplements
Mexican Yam "Hormone Substitute"
Multi-level Multiple Vitamins
Coral Calcium
Supplement Quality
Vaccines
Procedures
Physicians
Physician Evaluations
How to Talk to Your Doctor
Alternative Medical Treatments
Healthy Lifestyle Support Group
Section titled “Healthy Lifestyle Support Group”"Creating Your Healthy Lifestyle", an 8 week educational support group starting March 6, will help you make lasting changes to improve your health. First, this class will help you understand the choices you currently make. Next, you will learn simple and effective techniques to develop healthy habits and create the life you most want.
Group facilitator Christine Nock, MA, LMHC addresses specific issues such as weight, stress, activity, self-care, and other behaviors that impact your health.
Find out more by calling 360-821-1407. The class runs from 4:30 to 6:30 pm Thursdays, and is limited to six people. Register now for this life changing group.
Influenza
Section titled “Influenza”According to the Centers for Disease Control, influenza activity is increasing. Here in Port Townsend we are seeing more frequent and more severe influenza-like illness. We have a few doses of vaccine remaining, which are available at a mid-season discounted price of $18. Please call 385-5658.