Would measurement of C-reactive protein reduce the rate of negative exploration for acute appendicitis?

Appendicectomy for suspected acute appendicitis is a common procedure. The rate of normal appendices unnecessarily removed remains high (15-30%) despite several techniques and investigations used to improve the diagnostic accuracy. Many studies investigated the role of raised C-reactive protein in improving the diagnosis of acute appendicitis, but with conflicting results. This study emphasies the impact of a normal (rather than raised) serum C-reactive protein in reducing the rate of negative explorations.

In a double blind study, blood for the measurement of serum C-reactive protein (CRP) was collected pre-operatively from 78 patients just before going to the operating room for appendicectomy. The histopathology of the 78 appendices were grouped into positive (acute appendicitis) and negative (normal appendix). White blood count (WBC), CRP and the histopathology findings were correlated.

In patients with histopathologically proven acute appendicitis both the WBC count and serum CRP level were significantly raised (P = 0.025 and P < 0.000,1 respectively). Serum CRP level was normal in 13 out of 15 negative explorations (normal appendix on histopathology). The specificity and sensitivity of serum CRP was 86.6% and 93.6%, respectively.

A normal pre-operative serum CRP measurement in patients with suspected acute appendicitis is most likely associated with a normal appendix. Deferring surgery in this group of patients would probably reduce the rate of unnecessary appendicectomies.