A pediatric appendicitis risk calculator (pARC) accurately quantified the risk among children and adolescents presenting to an emergency department with acute abdominal pain, researchers say.

“Until now, the diagnosis of appendicitis in children has heavily relied on diagnostic imaging such as computed tomography,” Dr. Anupam Kharbanda of Children’s Minnesota in Minneapolis told Reuters Health.

“CT scans can put pediatric patients at risk for radiation-induced injuries and unnecessary imaging drives up health care expenditures,” he said by email. “This calculator may help clinicians to make a more accurate diagnosis, thus reducing the use of CT and reducing health care spending.”

Dr. Kharbanda and colleagues developed and validated the calculator through secondary analyses of three cohorts of children who went to a pediatric emergency department with acute abdominal pain. The derivation sample included 2,423 children ages 5 to 18, 40 percent of whom had appendicitis.

The validation sample, derived from two independent cohorts, included 1,426 children ages 5 to 18, 35 percent of whom had appendicitis.

The final pARC model used the following variables to help assess risk: sex, age, duration of pain, guarding, pain migration, maximal tenderness in the right-lower quadrant, and absolute neutrophil count.

As reported in Pediatrics, the pARC exhibited “near perfect calibration” in the validation sample and a high degree of discrimination (area under the curve [AUC]: 0.85; 95% confidence interval 0.83–0.87), outperforming the Pediatric Appendicitis Score (AUC: 0.77; 95% confidence interval 0.75–0.80).

“Importantly,” the authors note, “in our validation cohort with a background risk of appendicitis of 35 percent, the pARC score was able to classify half of patients as [having at least an 85 percent risk or less than a 15 percent risk] for appendicitis, thresholds where surgical evaluation or observation, respectively, may be recommended over immediate diagnostic imaging.”

Only 23 percent of patients would have been identified as having a comparable Pediatric Appendicitis Score of <3 or >8.

Dr. Kharbanda said, “Next steps include a validation of the calculator in community emergency departments in Minnesota, Wisconsin, and California. We are also developing a mobile application to allow for widespread dissemination of our pARC nationally.”

Dr. Shari Platt, chief of pediatric emergency medicine at NewYork-Presbyterian and Weill Cornell Medicine in New York City, commented, “This [calculator] would be very needed, especially for less experienced providers, general pediatricians, and emergency physicians who care for children in acute care settings.”

“A missed appendicitis is one of the most common lawsuits in our field,” she said in an email to Reuters Health, “and having a reliable and validated clinical tool to help guide the evaluation would be very valuable.”

“Caveats are that it requires lab testing, so children who do not have lab studies performed will not be included,” she noted. “It also needs sophisticated calculations, which may be a barrier, but can be easily programmed into an electronic system.”

“At present, the guideline for evaluating a child with appendicitis is based on clinical judgment and experience,” she said. “This calculator provides an objective measurement of risk, and thus may be applied and/or integrated into clinical practice, with an understanding of its limitations.”

Dr. Ethan Wiener, associate chief in the Division of Pediatric Emergency Medicine at Hassenfeld Children’s Hospital at NYU Langone Health in New York City, said, “Coming from authors who have done a great deal of the important appendicitis work in the last decade, this paper is an effort to develop a better clinical prediction rule for appendicitis.”

“The real question with this rule is applicability,” he told Reuters Health by email. “The lowest-risk groups identified, [with] <5 percent and 5 percent–15 percent risk, have somewhere between a 1 in 10 to 1 in 20 risk of appendicitis.”

Most clinicians would still want to pursue a diagnosis at those levels of risk, he said, given the “significant implications and potential for complications.”

Dr. Wiener added that in his experience, equivocal ultrasounds do not necessarily lead to more CT scans. “Having a patient in the ED undergoing a workup gives us an opportunity to re-examine him or her,” he said. Longer observation may occur in some cases, possibly leading to another ultrasound or surgery or, he acknowledged, a CT scan if indicated.

“It seems like we must continue to rely on the age-old and time-tested physical exam findings of right lower-quadrant pain and associated peritoneal findings to guide clinical impressions and subsequent determination of need for diagnostic work-up,” he concluded.

Dr. S. Daniel Ganjian of Providence Saint John’s Health Center in Santa Monica, California, added, “This study was performed only on patients presenting to a children’s hospital.”

“Validation studies need to be performed to see if this tool can be used on patients who present to the pediatrician’s office or general ED, as opposed to specifically a pediatrics ED,” he said by email.