CRP in acute appendicitis--is it a necessary investigation?

Appendectomy is one of the commonest procedures in surgery. In spite of various investigations used to improve the accuracy of diagnosis, the rate of normal appendices removed is still about 15-30%. Many studies have investigated the role of C-reactive protein (CRP) in acute appendicitis, but with conflicting results.

In a prospective, double blind study, blood for the measurement of serum C-reactive protein was collected pre-operatively from 192 children before going to the operating theatre for appendectomy. The histopathology was grouped into positive (acute appendicitis) and negative (normal appendix) and this was correlated with CRP values.

CRP was normal in 14 out of 33 negative explorations (normal appendix on histopathology). The specificity and sensitivity of serum CRP was 42% and 91% respectively. The predictive value of a positive (raised CRP) and negative (normal CRP) test is 88% and 48% respectively.

We conclude that neither raised nor normal CRP value is helpful in the diagnosis of acute appendicitis. CRP is not a good tool for helping the surgeon make the diagnosis of appendicitis and it should not be measured in suspected appendicitis.