C-reactive protein and leukocyte count in the diagnosis of acute appendicitis in children

PURPOSE: The aim of this study was to analyze the diagnostic accuracy of C-reactive protein and its possible advantage, if any, over leukocyte counts in acute appendicitis in children. METHODS: We performed a retrospective study of 124 children (72 males) with a mean age of 9.3 (range, 2–14) years operated on under a clinical diagnosis of acute appendicitis. The diagnosis of acute appendicitis, confirmed by pathologic examination of the removed appendix, was then correlated with C-reactive protein, leukocyte count, and a combination of both C-reactive protein and leukocyte count, with a logistic regression model. C-reactive protein serum measurements were performed by an immunoturbidimetric test. The patients were divided into two groups according to the pathologic features of the removed appendix: Group A (n=104), patients with acute appendicitis, and Group B (n=20), patients without acute appendicitis. To assess the accuracy of C-reactive protein, leukocyte counts, and a combination of both parameters, receiver operating characteristic curves were used. The areas under the curve were compared using the maximum likelihood estimation method. RESULTS: There were 95 cases (76.6 percent) of nonperforated appendicitis, 9 cases (7.3 percent) of perforated appendicitis and 20 cases (16.1 percent) of normal appendix. Mean C-reactive protein in Group A was 4.3 (standard deviation, 6.6) and in Group B was 1.2 (standard deviation, 1.7;P=0.03). The C-reactive protein and leukocyte count values were correlated with the pathologic diagnosis of acute appendicitis. Mean C-reactive protein values increase as the pathologic inflammation type progresses (P=0.007). The C-reactive protein receiver operating characteristic curve shows that the C-reactive protein value with highest accuracy was 1.7 mg/dl. The sensitivity, specificity, and accuracy rates calculated in the 1.7 cutoff were 58, 80, and 83.8 percent, respectively. A comparison of the respective receiver operating characteristic curves demonstrates that C-reactive protein, leukocyte count, and the combination of both tests all have a good diagnostic value but without any significant difference (P=0.2). CONCLUSIONS: In children, 1) serum C-reactive protein is increased in acute appendicitis; 2) such increase is related to the severity of the appendiceal inflammation; and 3) although serum C-reactive protein has an adequate diagnostic accuracy, neither individually nor in combination with the leukocyte count is it significantly better than the leukocyte count alone.