CT represents a highly sensitive and specific test for diagnosing appendicitis, with an increase in in CT appendicitis testing associated with a decrease in the surgical perforation rate, suggesting that CT should became the standard of care for suspected appendicitis, according to a study published June 20 in the Annals of Internal Medicine.
The use of CT in cases of suspected acute appendicitis increased dramatically following the introduction of multidetector CT (MDCT) in 1999, from utilization at 20 percent of cases in 2000 to as many as 90 percent in 2006, according to previous research.
“To our knowledge, relatively few studies have evaluated the diagnostic performance of CT in the multidetector era for acute appendicitis in adults. High test sensitivity is critical to efficiently identify all patients who need appendectomy, but it is also desirable to avoid unnecessary surgical procedures,” noted Perry J. Pickhardt, MD, from the department of radiology at the University of Wisconsin School of Medicine and Public Health in Madison, and co-researchers.
The authors retrospectively reviewed the medical records of 2,871 patients who presented with suspected acute appendicitis between 2000 and 2009, comparing CT findings to the surgical pathology report, which served as the reference standard, as well as intraoperative findings and clinical follow-up.
Acute appendicitis was confirmed in 675 of 2,871 patients, with a 19 percent prevalence in women and 31 percent in men. This difference was attributed to patient selection and overall differences in incidence, not CT performance.
CT delivered a sensitivity of 98.5 percent and a specificity of 98 percent, along with a negative predictive value of 99.5 percent and a positive predictive value of 93.9 percent, according to Pickhardt and colleagues.
The researchers noted that if surgery been avoided in all true-negative CT findings, the rate of negative findings at appendectomy would have decreased from 7.5 percent to 4.1 percent. Sixteen of the 1,958 patients with “definitely negative” findings on CT nonetheless underwent appendectomy, 12 of whom showed negative pathology and four were positive for appendicitis.
The annual perforation rate fell from 29 percent in 2000 to 12 percent in 2009, which Pickhardt and colleagues said suggested earlier diagnosis and treatment. The authors could not determine whether this decline in the perforation rate was related to the concomitant increase in the volume of CT for suspected appendicitis.
Ten false-positive CT reports were discovered, which accounted for 0.35 percent of the study cohort. Twenty patients presented with appendicitis on CT but did not undergo appendectomy or receive a clinical diagnosis, and were therefore considered to be false-positive cases.
Pickhardt and co-authors noted that a 15 to 20 percent rate of negative findings at appendectomy was once considered acceptable, but with the hospital’s increasing utilization of CT for suspected appendicitis, its rate had fallen to below 10 percent.
“Our study, which, to our knowledge, represents the largest CT-based cohort for suspected appendicitis, shows a high sensitivity and specificity for MDCT, which corresponds to measurable clinical benefit,” the authors stated.
Pickhardt and colleagues did acknowledge that the generalizability of their findings was limited by the study including only one hospital, as well as the inherent limitations associated with retrospective investigations.
Nonetheless, the authors concluded, “These results, in conjunction with recent data from surgical cohorts suggesting benefit related to increased use of MDCT [multidetector CT], support routine use of preoperative MDCT as the standard of care for suspected appendicitis in adults.” The effect of doing so, Pickhardt and colleagues argued, would be reduced rates of perforation and negative findings at appendectomy, as well as the appropriate redirection of clinical management for patients with other diagnoses.