Cost of MR outweighs CT radiation risks for suspected appendicitis

When it comes to diagnosing appendicitis in adult patients, recent research has found that despite CT radiation concerns, life expectancy loss across various imaging modalities was so small that paradigm shifts in radiology were found unnecessary.

Sorapop Kiatpongsan, MD, PhD, from Harvard University, and colleagues set out to answer how decision makers could select the best imaging modality for diagnosing appendicitis and how much radiation concerns should factor into their decision. Their results were published this month in Radiology.

“Each imaging modality’s test performance—and not their associated radiation-induced cancer risks—determined their relative ranking in terms of life expectancy loss,” researchers said.

Using a decision-analytic model, the team assessed long-term effects associated with three imaging strategies for patients suspected of having appendicitis. These imaging modalities included CT alone, combined CT and ultrasound (US), and MR imaging alone.

Kiatpongsan and colleagues established life expectancy loss associated with each imaging technique as the primary outcome measure. They incorporated expected days of life lost attributable to surgical mortality, missed appendicitis, radiation-induced cancers and competing age- and sex-based mortality risks.

Base analysis was performed on a cohort of 20-year-old men, with additional cohorts of men and women being further evaluated in a sensitivity analysis.

Based on results from the base-case cohorts, researchers found the life expectancy loss differences across the different imaging strategies in a hypothetical cohort of men suspected of having acute appendicitis was minimal:

• CT alone: 8.2 days
• US and CT combined: 6.8 days
• MR: 5.8 days

When the research team varied the prevalence of appendicitis across a wide range, MR imaging was associated with the least life expectancy loss by a small margin.

In light of the low variance across imaging modalities, researchers did suggest benefits associated with investing in infrastructure and training to sustain high-level MR imaging performance due to its higher sensitivity and accuracy.

“In our analysis, MR imaging was associated with the least [life expectancy] loss, but required very high test performance characteristics to retain this standing—for example, sensitivity of 91 percent or greater and specificity of 62 percent or greater in 20-year-old men,” researchers said.

However, given the minimal life expectancy gains achievable by MR imaging relative to CT-based strategies, MR imaging is not likely to be cost-effective in this setting from a societal standpoint.

“In the setting of suspected appendicitis in adults, concerns over radiation exposure from CT should not directly translate into paradigm shifts toward MR imaging,” Kiatpongsan and colleagues said.