To Scan or Not to Scan: The Use of CT
July 4, 2010 4 Comments
Margaret Polaneczk writes in her piece Was it Defensive Medicine or a Necessary Test? about the CBS news story from a couple of years ago regarding a college student who had a CT scan in the emergency department which revealed an ovarian cyst. This has inspired me to address the issue of the CT scan again. Refer to an earlier entry, On CT Scans, which addresses some of the more recent articles in the New England Journal of Medicine.
First, let’s look at the facts: the frequency of CT scans in this country has increased astronomically over the last two decades. There are now over 70 million scans done in the United States per year – this is 23 times the number of scans done in 1980. Although the jury is still out on the exact degree of malignancy risk, its presence is undeniable. For a pediatric head CT, the risk of developing fatal cancer falls somewhere between 1:1000 and 1:5000. For abdominal CT scans on a 25-year-old, the risk of cancer is approximately 1 in 900 and the risk of fatal cancer is approximately 1 in 1800. For a 50-year-old, these numbers decrease to 1 in 1500 and 1 in 2500, respectively. As age increases, risk decreases. The approximate number of deaths attributable to CT scan annually in the United States is 700 for head scans and 1800 for abdominal scans, with 170 and 310 of these accounting for pediatric deaths (Brenner D., et al. Estimated risks of radiation-induced fatal cancer from pediatric CT. AJR Am J Roentgenol 2001; 176:289-296).
The cost of a CT scanner is $500,000, but hospitals keep these scanners for up to three years or more and amortize the cost over this period. There are about 6000 CT scanners in the United States – with 70 million scans done annually, that amounts to 11,700 CT scans per machine. This varies depending on hospital size. I would imagine that larger academic hospitals perform in the range of 20,000 to 30,000 CT scans per year. The marginal cost to run the CT machine is minimal – between $30 and $50 dollars a scan, so the average total revenue for the hospital from CT scans is quite high – approximately $400 per scan. This amounts to $4.7 million in revenue from CT scans alone.
Whether or not cost should be factored into this analysis is debatable, but the bottom line is that the marginal cost of a single CT scan is relatively low, even though the cost to patients (or insurance companies) ranges from $1200 to $3200.
When it comes to something like abdominal pain, new studies (Imaging strategies for detection of urgent conditions in patients with acute abdominal pain: diagnostic accuracy study) have demonstrated that performing an abdominal ultrasound first not only increases diagnostic accuracy but also allows physicians to avoid CT scans if they can make a definitive diagnosis on ultrasound. Another study (Identification of children at very low risk of clinically-important brain injuries after trauma) indicates certain essential elements of a good history and physical can provide physicians with enough evidence to avoid head CTs in pediatric trauma.
As emergency physicians become better skilled in ultrasound use, we can make quick diagnoses at the bedside rather than having patient care delayed due to additional studies. Ultrasound is a cheap, safe, portable, and is an effective method for evaluating patients with possible ovarian torsion, cholecystitis, hydronephrosis, congestive heart failure, and sometimes even appendicitis – especially in children. It has essentially become a new part of the physical exam for physicians who are adept in its use. It is the modality of choice in the emergency department, where efficiency and accuracy are of utmost importance. As we become more skilled in its use, my hope is that we will be able to decrease the number of unnecessary CT scans and to accelerate the process of appropiate diagnosis and treatment.