Combining lab data with ultrasound could cut CT use in pediatric appendicitis patients

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Adding white blood cell (WBC) count and polymorphonuclear leukocyte differential (PMN%) to already existing ultrasound screening technology improves predictive diagnosis of appendicitis in children, according to a study published online Jan. 31 in the Journal of the American College of Surgeons.

Appendicitis accounts for more emergency abdominal surgeries among the pediatric population than any other ailment, yet diagnosis through examination and pathology remains a formidable challenge for clinicians, according to lead author Seema P. Anandalwar, MD, and colleagues at Boston Children’s Hospital. “The poor diagnostic yield of clinical and laboratory data has led to an ongoing reliance on diagnostic imaging, including ultrasound, CT, and MRI,” wrote Anandalwar et al. “With increasing public health concern surrounding radiation exposure, and mounting pressure from national specialty organizations to limit the use of CT, US is the preferred initial imaging modality in the evaluation of children with suspected appendicitis.”

The researchers set out to determine what effect the incorporation of WBC count and PMN% could have on the predictive abilities of ultrasound in the diagnosis of pediatric patients with appendicitis. They performed a retrospective analysis of laboratory data and imaging results of 845 children who underwent ultrasound screening for suspected appendicitis between Jan. 1, 2010, and Dec. 31, 2012, at the team’s pediatric hospital. Positive and negative predictive values for appendicitis were determined for common ultrasound constellations, then compared with and without patient WBC count and PMN% laboratory thresholds. 

Their results revealed that 51 percent of the ultrasound scans incompletely imaged the appendix and found no primary or secondary signs of the disease, with negative predictive values increasing from 42 percent to 95 percent when including the laboratory thresholds. Primary signs for appendicitis were discovered in 18 percent of scans, with the positive predictive value for the cohort increasing from 79 percent to 91 percent with lab data. Just under one-quarter of examinations discovered only secondary signals, with lab thresholds raising positive predictive values among the group from 89 percent to 96 percent.

Overall, the research team concluded that combining WBC counts and PMN% with ultrasonography diagnostic strategies would have reduced the number of pediatric CT scans by 27 percent over the study’s duration.

That number could hold great promise for patients with pediatric appendicitis, according to Anandalwar and her colleagues. “Through the approach of combining laboratory and (ultrasound) data, we were able to identify cohorts of patients with a relatively high and low risk for appendicitis, which can be targeted for guidelines to reduce resource use and radiation exposure,” the authors wrote. “The conceptual approach described in this study for characterizing predictive profiles on the basis of laboratory and sonographic data is likely to be generalizable to many, if not all, hospitals that treat appendicitis in the pediatric population.”