Accuracy of serum c-reactive protein measurements in diagnosis of acute appendicitis compared with surgeon's clinical impression

Abstract

Diagnosis of acute appendicitis is established generally by the surgeon's clinical impression. Today, negative laparotomy rate because of clinical diagnosis is still 15 to 25 percent. This study was designed to determine the accuracy of C-reactive protein (CRP) measurements in the diagnosis of acute appendicitis and to compare it with the surgeon's clinical diagnosis. One hundred eight consecutive patients were studied prospectively. Depending on results of the examination by a surgeon, patients underwent surgery for acute appendicitis. Serum CRP measurements were performed before the operations but were not taken into account for the decision of laparotomy to compare it with the surgeon's clinical diagnosis. Histopathologic findings confirmed acute appendicitis in 90 patients. Normal appendixes were removed in the remaining 18 patients. Mean serum CRP value was 5 (range, 0-12.6) mg/l in patients with normal appendix, 33.8 (range, 5-85.1) mg/l in patients with nonperforated appendicitis, and 128.5 (range, 79.2-230) mg/l in patients with perforated appendixes. These differences were highly significant (P < 10(-6)). Serum CRP levels were normal in three patients with acute appendicitis. Thus, the false-negative rate of CRP was 3 percent. Of 18 patients with normal appendectomy serum CRP levels were slightly elevated in two patients. We determined, therefore, a false-positive rate of CRP as 11 percent. CRP levels were false-negative in three patients and false-positive in two patients. Thus, CRP levels were true (positive or negative) in the remaining 103 patients. On the other hand, the diagnosis depending on surgeon's clinical impression was true in 90 patients and false in 18 patients. This difference was statistically significant (P = 0.0035). In the present study the sensitivity, specificity, and accuracy of serum CRP measurements were calculated as 93.5, 80, and 91 percent, respectively. We found that elevated serum CRP levels support surgeon's clinical diagnosis. We recommend CRP measurement as a routine laboratory test in patients with suspected diagnosis of acute appendicitis.