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

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.

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.

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).

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.