Adult patients who score a “3” or lower on the Alvarado point-scale should not be considered at risk for appendicitis and are unlikely to benefit from additional CT testing, according to results of a study published in the March issue of the American Journal of Roegentology.

Patients who present with pain in the lower right quadrant are typically assessed using either graded-compression ultrasound or abdominal CT. In light of efforts to limit excessive imaging and thereby reduce patient exposure to radiation, many doctors have begun advocating for ultrasound as the first modality of choice for assessing these patients.

There’s just one problem with this proposed solution, according to lead author Robert Jones, MD, and his colleagues from the Stanford University School of Medicine. “A major shortcoming of ultrasound as the initial imaging study is its inability to detect the appendix in 12–69 percent of patients overall and in as many as 97.6 percent of patients with normal appendixes, thus providing no certain imaging information about the appendix in a considerable proportion of patients.” In these situations, results of the ultrasound are often considered inconclusive, and patients are referred for additional CT testing.

For this reason, doctors often determine the best course of treatment using patients’ Alvarado scores, which are calculated using “a combined clinical and laboratory point scale that quantifies the potential likelihood of appendicitis.” Patients who score a “3” or less on this scale are considered to be at low risk for appendicitis.

Jones and his team set out to test the hypothesis that patients whose appendixes were not visible on ultrasound and have an Alvarado score of 3 or less are unlikely to benefit from additional CT imaging. To do so, he and his team identified 119 consecutive patients from their medical facility who matched this criteria and underwent subsequent CT testing within 48 hours of the initial ultrasound study.

Their results showed that none (0/49) of the patients with Alvarado scores of “3” or less were found to have appendicitis following CT, compared with 17 percent (12/70) of patients with a ”4” on the Alvarado point scale. Additionally, 86 percent of those same patients (42/49) were found to have no alternative significant findings after undergoing CT testing, compared to just 59 percent (41/70) in the latter group of patients.

“An Alvarado score of 3 or lower reliably distinguished at a statistically significant level the patients who did not receive specific benefit from post-sonography CT from those patients who did,” wrote Jones et al, “supporting the original hypothesis that Alvarado scores of 3 or less would function in this fashion.”

While the researchers believe the Alvarado scoring system can greatly reduce scans for suspected appendicitis by pinpointing patients unlikely to benefit from additional CT testing, they caution against avoiding the modality entirely based on their findings.

“The proposed method does not suggest avoiding CT altogether but rather suggests using it in a deliberate fashion with knowledge of the small likelihood that it will reveal appendicitis or significant alternative findings,” Jones and his colleagues wrote. “If prospective studies corroborate the present findings, it may be possible to use the Alvarado score to avoid CT and its corresponding radiation burden in some of these clinically challenging patients.”