Lowering the threshold of white blood cells (WBC) to the range of 8,000 per µL to 9,000 per µL as a diagnostic criterion for appendicitis can reduce the rates of negative appendectomies (NA) in children to less than 1 percent, according to a study published in the January issue of Pediatrics. While maximum sensitivity has always been emphasized in diagnosis of appendicitis, given the significant negative consequences associated with a missed case of true appendicitis, the national rate of NA remains over 3 percent in the United States. Given the commonness of appendicitis, this NA rate indicates a large number of unnecessary surgeries, which do carry some risks to children. In an effort to further decrease the false-positive rate associated with appendectomies, researchers retrospectively reviewed all appendectomies performed for suspected appendicitis at a tertiary children’s hospital over a 42-month period with regard to preoperative clinical, laboratory, and radiographic data. Over the study period, 847 appendectomies were performed with 2.6 percent (n=22) having a pathologically normal appendix, or NA. WBC count and neutrophil count were found to be normal in more than three-quarters of the NAs (89 percent and 79 percent, respectively). Applying WBC cutoffs of 9,000 per µL and 8,000 […]
Lowering the threshold of white blood cells (WBC) to the range of 8,000 per µL to 9,000 per µL as a diagnostic criterion for appendicitis can reduce the rates of negative appendectomies (NA) in children to less than 1 percent, according to a study published in the January issue of Pediatrics.
While maximum sensitivity has always been emphasized in diagnosis of appendicitis, given the significant negative consequences associated with a missed case of true appendicitis, the national rate of NA remains over 3 percent in the United States. Given the commonness of appendicitis, this NA rate indicates a large number of unnecessary surgeries, which do carry some risks to children.
In an effort to further decrease the false-positive rate associated with appendectomies, researchers retrospectively reviewed all appendectomies performed for suspected appendicitis at a tertiary children’s hospital over a 42-month period with regard to preoperative clinical, laboratory, and radiographic data.
Over the study period, 847 appendectomies were performed with 2.6 percent (n=22) having a pathologically normal appendix, or NA. WBC count and neutrophil count were found to be normal in more than three-quarters of the NAs (89 percent and 79 percent, respectively). Applying WBC cutoffs of 9,000 per µL and 8,000 per µL achieved sensitivities of 92 percent and 95 percent, respectively, and reduced the NA rates by 77 percent and 36 percent, respectively.
These anticipated sensitivities and specificities were confirmed looking at 204 cases in the subsequent 12 months. During this period there were two NAs (0.98 percent). In these patients, WBC counts on admission were 6,400 per µL and 8,200 per µL, yielding a false-positive rate of 0 percent using the 9,000 per µL cutoff and 0.5 percent for the 8,000 per µL cutoff. There were 18 patients over the same period with true appendectomies with WBC counts less than 9,000 per µL, with six of these patients having WBC counts less than 8,000 per µL. For WBC cutoffs of 9,000 per µL and 8,000 per µL, the observed sensitivities were 91 percent and 97 percent, respectively, which was not statistically different from the expected values.
“Using the WBC count as a continuous variable, rather than as a true/false measure of leukocytosis, may help us reduce our NA below 1 percent without significantly affecting the sensitivity of our diagnosis,” conclude the authors, led by Maria Bates, M.D., from the Alpert Medical School of Brown University (Providence, R.I.). “WBC count cannot reasonably be used as the sole determinant of acute appendicitis at the exclusion of all others. . . . However, a WBC count <8,000 to 9,000 per µL in a child who has had symptoms for <24 hours merits a period of observation, provided there are no signs of advanced disease.”
