SAN FRANCISCO — The diagnosis of appendicitis is notoriously difficult in children, with estimates of misdiagnosis rates ranging from 28% to 57% for children over the age of 12 and up to 100% for children under 2 years of age.
But the diagnosis may be made with high specificity using a combination of C-reactive protein and white blood cell levels, suggest the findings of a poster presented by Dr. Karen Y. Kwan and Dr. Alan L. Nager at the annual meeting of the Pediatric Academic Societies.
In particular, a C-reactive protein (CRP) level of 1.0 mg/dL or greater combined with a WBC count of 15,000 cells/mm
The study, conducted at the University of Southern California, Los Angeles, involved 209 patients aged 1–18 years presenting at a tertiary urban children's hospital with abdominal pain suspicious for acute appendicitis. In addition to history, physical exam, x-ray studies, and histopathology, the investigators conducted blood tests for CRP, WBC, D-lactate, and procalcitonin. Two to 6 weeks following discharge from the emergency department, investigators followed up with the patients to determine the ultimate diagnosis.
Of the 209 patients, 115 (55%) had confirmed appendicitis and 94 (45%) were negative. Among the diagnoses for children negative for appendicitis were constipation, gastroenteritis, pyelonephritis, ovarian torsion, and neoplasm.
The mean D-lactate values did not differ between patients who were positive and negative for appendicitis. The values of the other three lab markers did differ significantly; in each case patients with appendicitis had a significantly higher level than patients without.
Using a cutoff value of 1.0 mg/dL of CRP alone would yield a sensitivity of 84% and a specificity of 70%. A combination of that CRP cutoff with a WBC cutoff greater than 15,000 cells/mm
The investigators advised interpreting their findings with caution as 85% of the patients were Hispanic and largely indigent, and acute or chronic diseases may skew the laboratory values.
The meeting was sponsored by the American Pediatric Society, the Society for Pediatric Research, the Ambulatory Pediatric Association, and the American Academy of Pediatrics.