rationale for testing

Monday, November 7, 2011

Usually, the news that Dr. James Andrews makes is in relation to the injury and repair of an elite athlete. However, the story this week has to do with why high tech takes second place to physical examination when it comes to diagnosing injuries. MRI scans of healthy pro pitchers who had no complaints were universally abnormal and potentially were misleading. The technology involved may be cutting edge, but it is old news when talking about the usefulness of medical tests. Whether it is a blood test or x-ray, the doctor needs to know when a test will help make the diagnosis and what to do with the results.

Dr. Andrews’ findings have been supported by other orthopedic doctors around the country who have found that many patients are referred MRI scans in hand even though the diagnosis could be made clinically. There is increasing pressure on doctors by patients to use technology to confirm their clinical diagnosis; it’s as if the skill in taking a history and performing a physical examination is no longer trusted. Unfortunately, the patient may not appreciated that there is also great skill in deciding when testing is appropriate and how to interpret those tests.

The CBC, a complete blood count that measures red blood cell, white blood cell and platelet counts, is commonly ordered in many clinical situations. The results need to be put in context. Elevated white blood cell counts can occur in patients with bacterial infections unless the patient is septic, meaning the infection has spread throughout the body. The WBC may be very low since the infection may have overwhelmed the body’s ability to fight it. The count may be normal in the face of infection if the patient is immune compromised because of an underlying illness like cancer or if medications like steroids are being taken that prevent the body from mounting a WBC response. The test provides direction but needs to be interpreted in light of the patient’s situation.

The amount of bleeding should be relatively easy to measure. Part of the CBC is a red blood cell count but a single normal measurement in a bleeding patient can be misleading. If a patient loses a significant amount of blood, a blood test done immediately would be normal. It takes a little time for the body to adapt to the bleeding and maintain blood pressure and blood flow by shifting water into blood vessels. That dilutes the remaining red cells causing the red blood cell counts to fall. Relying on only a single blood test might falsely reassure the doctor that the patient is more stable than they really are. Careful physical examination may find abnormal postural vital signs, where he blood pressure falls and the pulse rate increases when taking laying and standing. It’s not always that simple. A patient taking beta-blocker medication like Atenolol, which blocks the adrenalin response, may not be able to mount a heart rate increase.

Abdominal CT scans can make the diagnosis of appendicitis, but if may take 6-12 hours for enough inflammation to develop to be seen on CT. If the scan is done too early, then it may be falsely normal. And the scan may be unnecessary if the story and physical examination are enough to convince the surgeon that the diagnosis of appendicitis is appropriate and an operation is needed. Patients may or may not be willing to accept the recommendation for surgery without the CT test and yet, they would be trustful of that same person to make the incision in their body.

Both doctor and patient need to listen to each other. It is a cooperative effort to come to a diagnosis and treatment plan. The doctor may not need technology to make a decision but the art of medicine requires that the doctor teaches and the patient understands how that decision was made. And the patient is responsible for telling the doctor what fears they might have and how they think technology might help. While technology might help, it’s all about trust.

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