Diagnostic accuracy of blood tests for paediatric appendicitis, a systematic review and meta-analysis

Gea Holtman, David Fawkner-Corbett, Gail Hayward, Mohammed Alkhmees, Jose Ordonez-Mena, Ann Van Den Bruel

Keywords: Blood tests; Appendicitis

Background:

Possible appendicitis in children is a common emergency presentation. The exact value of blood tests in these children is debated.

Research questions:

What is the diagnostic accuracy of white cell count (WCC), neutrophil (count or percentage), C-reactive protein, and/or procalcitonin for paediatric appendicitis?

Method:

For this systematic review and diagnostic meta-analysis, MEDLINE, EMBASE, Central, Web of Science were searched from inception to March 2022 with reference searching and authors were contacted for missing/unclear data. We included studies reported on the diagnostic accuracy of the four blood tests compared to the reference standard histology or follow-up. Risk of bias was assessed (QUADAS-2), pooled sensitivity and specificity were generated for each test and for commonly presented cut-offs. To provide insight into clinical impact, we present several strategies using a hypothetical cohort of children suspected of appendicitis.

Results:

67 studies were included (34,839 children, 13,342 with appendicitis), all were in the hospital setting (73% in emergency department). The most sensitive tests were WCC (≥10,000 cells/μl, 53 studies, sensitivity 0·85 [95% CI 0·80-0·89]) and absolute neutrophil count [ANC] (≥7,500 cells/μl, five studies, sensitivity 0·90 [95% CI 0·85-0·94]). Applying results to a hypothetical cohort of 1000 children presenting with symptoms of appendicitis, of whom 400 have appendicitis, 60 and 40 children would be wrongly discharged based solely on WCC and ANC, respectively. The most specific tests were CRP alone (≥50mg/l, 38 studies, specificity 0·87 [95% CI 0·80-0·91]) or combined with WCC (≥10,000 cells/μl and CRP ≥50mg/l, individual patient data of six studies, 0·93 [95% CI 0·91-0·95].

Conclusions:

The best performing blood tests for ruling-out paediatric appendicitis are WCC or ANC. With technology developing at pace these tests could be used at the point of care in combination with clinical prediction rules at the emergency department. Studies are needed to evaluate the diagnostic accuracy of these tests in primary care.

Points for discussion:

What would be the value of these tests in primary care?

Which test would be most applicable in primary care?

#71