Clinical and laboratory findings in the diagnosis of right lower quadrant abdominal pain: outcome analysis of the APPAC trial.

Background: The current research on acute appendicitis aims to improve the diagnostics and to clarify to whom antibiotic treatment might be the treatment of choice.

Methods: The present study is a retrospective analysis of a prospectively collected data in our randomized multicenter trial comparing surgery and antibiotic treatment for acute uncomplicated appendicitis (APPAC trial, NCTO1022567). We evaluated 1321 patients with a clinical suspicion of acute appendicitis, who underwent computed tomography (CT). Age, gender, body temperature, pain scores, the duration of symptoms, white blood cell count (WBC) and C-reactive protein (CRP) were recorded on admission.

Results: CT confirmed the diagnosis of acute appendicitis in 73% (n=970) and in 27% (n=351) it revealed no or other diagnosis. Acute appendicitis patients had significantly higher WBC levels than patients without appendicitis (median 12.2 and 10.0, respectively, p<0.0001), whereas CRP levels did not differ between the two groups. Ideal cut-off points were assessed with receiver operating characteristic (ROC) curves, but neither these markers or neither their combination nor any clinical characteristic could accurately differentiate between patients with acute appendicitis and those without. The proportion of patients with normal WBC count and CRP was significantly (p=0.0007) lower in patients with acute appendicitis than in patients without appendicitis.

Conclusions: Both clinical findings and laboratory tests are unable to reliably distinguish between patients with acute appendicitis and those without. If both WBC count and CRP are normal, acute appendicitis is very unlikely. The current results emphasize the role of CT imaging in patients with suspected acute appendicitis.