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

The aim of the present work was to study the preoperative leucocyte counts and C-reactive protein (CRP) values in three groups of patients operated on for a clinical suspicion of acute appendicitis with different findings at appendicectomy: an uninflamed appendix, uncomplicated acute appendicitis or complicated acute appendicitis. In particular, patients with acute appendicitis but a normal leucocyte count and CRP level were sought.

In this retrospective study, the mean preoperative leucocyte count and CRP value in 100 consecutive patients with an uninflamed appendix (group A), in 100 consecutive patients with uncomplicated acute appendicitis (group B) and in 100 consecutive patients with complicated acute appendicitis (group C) were calculated. The numbers of patients with (1) both values normal, (2) only leucocyte count raised, (3) only CRP level raised and (4) both values raised were calculated in each of the three groups.

The increase in leucocyte count was an early marker of appendiceal inflammation, whereas the CRP value increased markedly only after appendiceal perforation or abscess formation. Group A (uninflamed appendix) contained 24 patients in whom both values were normal. Neither group B (uncomplicated acute appendicitis) nor group C (complicated acute appendicitis) contained any patient with both values in the normal range.

Acute appendicitis is very unlikely when both the leucocyte count and CRP value are normal.