Shift to ultrasound for appendicitis could reap $21.8 million annual savings

December 1, 2010

U.S. hospitals could save nearly $22 million annually by deemphasizing CT in favor of diagnostic ultrasound as the frontline imaging test for suspected appendicitis. Such a change would also spare many patients unnecessary exposure to ionizing radiation from CT, according to financial evaluation and meta-analysis by Laurence Parker, Ph.D., an imaging economics researcher at Thomas Jefferson University in Philadelphia.

U.S. hospitals could save nearly $22 million annually by deemphasizing CT in favor of diagnostic ultrasound as the frontline imaging test for suspected appendicitis. Such a change would also spare many patients unnecessary exposure to ionizing radiation from CT, according to financial evaluation and meta-analysis by Laurence Parker, Ph.D., an imaging economics researcher at Thomas Jefferson University in Philadelphia. 

Because of its speed and accuracy, multislice CT has almost completely supplanted the traditional physical exam and diagnostic ultrasound for evaluating right lower quadrant pain suggesting appendicitis. At Thomas Jefferson University Medical Center, Parker found only 4% of patients presenting in the center’s emergency department with physical symptoms of appendicitis were referred for ultrasound. Everyone else received CT, noted Dr. Courtney Leigh Hoey, a radiology resident who presented Parker’s results Tuesday at the 2010 annual RSNA meeting.

Parker’s analysis considered the economic and radiation safety implications of shifting to diagnostic ultrasound for initial screening. His literature meta-analysis for the study found little difference between the accuracy of ultrasound and that of CT for evaluating right lower quadrant abdominal pain. The negative predictive values of ultrasound and CT were 91% and 92.5% respectively.

That finding suggested ultrasound was accurate enough to handle initial screening. All patients with a positive ultrasound could be directed to surgery. He proposed CT be performed to confirm negative ultrasound findings.

To calculate the relative costs of current and proposed protocols, Parker drew data from the Center for Medicare and Medicaid Services’ carrier, inpatient, and beneficiary files and the Physician/Supplier Procedure Summary Master Files for 2007.

In terms of utilization, the Medicare data indicated nearly two CT scans were performed on every Medicare beneficiary who presented in the ED with suspected appendicitis. As is the case at Thomas Jefferson, only four of every 100 patients nationally received ultrasound.

Parker found the average charge per patient for abdominal and pelvic CTs was $192 per patient compared with an average $38 for a limited ultrasound exam. From that, Parker determined that $153 per patient could be saved by shifting to ultrasound as the first-line test for appendicitis.

Medicare claims data, limited to a sample of 5% of beneficiaries, identified 650 cases of appendicitis and 863 of right lower quadrant pain in 2007. By assuming that all 1513 patients were initially admitted with right lower quadrant pain and that 569 true positives would be referred directly to surgery following ultrasound because of the modality’s 87.5% sensitivity, Parker calculated a $47,766 saving for the 5% sample and a total Medicare annual saving of $955,318.

By applying these estimates to the entire U.S. population, Parker proposed that $21.8 million could be saved annually by reserving CT for only those patients presenting with right lower quadrant pain who first had a negative ultrasound to evaluate their abdominal pain.

In terms of radiation dose, Parker determined the typical patient can expect to be exposed to 12.4 mSv (± 5.2 mSv) of radiation from an abdominopelvic CT scan. By extrapolating this estimate nationally, Parker estimated that shifting to an ultrasound-first protocol would spare the population from 3.2 million mSv of exposure annually. Using data from the BEIR VII (Biological Effects of Ionizing Radiation) radiation dose estimates of health risks from ionizing radiation, he predicted that an ultrasound-first policy would avoid 363 excess cancer cases annually and avoid 182 excess deaths from a solid tumor cancer and leukemia.

Errors could have arisen in the analysis by extrapolating Medicare data, which tracks the health experience of older Americans, to the entire population, Hoey said. Parker also assumed that right lower quadrant abdominal pain was the presenting symptom for appendicitis to generate estimates. The costs and mortality associated with excess surgeries associated with the slightly lower positive predictive value of ultrasound compared with CT was not included in the cost-savings calculation.