Blood tests in paediatric appendicitis have also been reviewed as part of a systematic review of other diagnostic modalities, with WCC identified as sensitive at 10 000 cells/μl (0.88%, 95% CI 87% to 90%) and CRP as specific (no pooled analysis).65 This did not include retrospective or non-ED studies, being limited to single studies at some cut offs. This evidence concerns the gene CRP and appendicitis.