Thursday, March 31, 2011

Too Many Diagnostic Tests? Says Who?

A recent Time magazine column attempted to analyze the reasons for the increased use of diagnostic imaging. The authors brought up many of the standard reasons including the need to practice defensive medicine, fallout from morbidity and mortality conferences, greed, etc. They say that doctors are no longer taught how to tell when patients need diagnostic tests and when they don’t. They make the following claim: “… the real value of so much testing has been widely questioned in scientific literature: imaging rates are going up, but doctors are not diagnosing (or necessarily misdiagnosing) more diseases.”

Respected medical blogger Kevin Pho (KevinMD) agreed with the Time article. Dr. Pho said that students are “…are spoiled by the easy access to the latest in imaging equipment and medical technology, and have become less dependent on physical exam skills previously relied upon in the past."

But as I have blogged previously, patients seem to want accurate diagnoses. Thus far, they are not moved by the theoretical increased risk of cancer secondary to radiation which may occur in the distant future. They want to know if they have appendicitis now and before they consent to surgery.

Contrary to what the Time magazine piece stated, there is some evidence that imaging does make the diagnosis of some diseases more accurate than history and physical examination.

In the April 2011 issue of the American Journal of Surgery, researchers from Howard University and the University of California, San Diego reported a 10-year review of negative appendectomy rates in the U.S. Using data from the National Inpatient Sample, they found that for nearly 500,000 appendectomies performed for presumed appendicitis from 1998 through 2007, the rate of removal of a normal appendix during surgery fell from 14.7% to 8.5%. This represents a 40% decline in the rate of negative appendectomy. The rate of perforated appendicitis also fell during that time period, indicating that the fall in negative appendectomy rates did not result in more occurrences of perforation.

Although the study was not designed to establish a link between the increased use of imaging studies and the falling rate of negative appendectomy, there are many papers supporting this conclusion such as one from Brigham and Women’s Hospital in Boston which showed a fall in the negative appendectomy rate from 23% to 1.7% over and 18-year period during which the rate of CT scan use went from 1% to 97.5%. Surgeons from Cornell reported similar results with the rate of CT scanning for appendicitis rising from 32% to 95% and the negative appendectomy rate falling from 16% to 7.65% from the late 1990s to the mid-part of the 21st century.

Having published a paper a few years ago which decried the use of CT scans in the diagnosis of appendicitis, I have completely reversed that opinion based on my personal series of over 125 appendectomies over the last two years with a negative appendectomy rate of just under 5%.

I never thought I would say this. The fact is CT scan is very accurate at diagnosing appendicitis. CT is better than I am and likely better than any human. It isn’t going to go away. It isn’t going to be replaced by ultrasound [not as readily available, not as accurate, not as easy to read] or MRI [not as readily available, not nearly as well-documented in the diagnosis of appendicitis, more expensive, not as easy to read]. So get over it.


Shannon Brownlee said...

The accuracy and need for CT to diagnose appendicitis depends upon the age and sex of the patient. A good ER doc should be able to diagnose most of the time without CT in men under 70. Women are trickier, but ultrasound can often distinguish between appie and ovarian cyst. But when surgeons insist on a CT before they'll cut, ER docs often comply. And the hospital makes out like a bandit.

Skeptical Scalpel said...

Th key word in your comment is "good."The clinical diagnosis of appendicitis remains difficult. I hope you had a chance to read my previous blog about this subject.

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