Trends in C reactive protein testing: a retrospective cohort study in paediatric ambulatory care settings.

OBJECTIVES: This study aims to investigate C reactive protein (CRP) testing practices in paediatric ambulatory care across British primary care and accident and emergency (A&E) departments. DESIGN, SETTING, PARTICIPANTS: This retrospective cohort study included children <18 years old having ≥1 CRP test at primary care or A&E departments in Oxfordshire between 2007 and 2021. OUTCOMES: We estimated the frequency and annual changes in CRP testing in both settings and evaluated referral and admission patterns based on CRP levels: low (<20 mg/L), intermediate or high (≥80 mg/L). RESULTS: Over 15 years, 91 540 CRP tests were requested in 63 226 children, with 33 882 (53.6%) in primary care and 29 344 (46.4%) in A&E. Both settings showed rising trends in test requests, with average annual percentage change of 3.0% (95% CI 1.2% to 4.7%) in primary care and 11.5% (95% CI 8.6% to 14.6%) in A&E. The proportion of intermediate/high-test results remained stable. In primary care, 50 709 (95.8%) of CRP tests were <20 mg/L, with 99.0% of these children managed at home. High and intermediate CRP values increased odds of referral versus low CRP (OR adjusted for age=21.80; 95% CI 16.49 to 28.81 and 4.77; 3.78 to 6.02, respectively). At A&E, 27 610 (71.5%) children had CRP<20 mg/L, of whom 42.5% were admitted while 3776 (9.8%) had CRP≥80 mg/L with 57.9% admission rate. High and intermediate CRP values increased odds of admission versus low CRP (OR adjusted for age=1.90; 95% CI 1.78 to 2.04 and 1.39; 1.32 to 1.46, respectively). CONCLUSION: There are rising trends of CRP test requests in paediatric ambulatory care settings, with no evidence of increases in proportion of intermediate/high-test results in primary care. Low CRP values at primary care were linked to children managed at home, while almost half of children with low CRP values at A&E were admitted to the hospital.

Diagnostic accuracy of blood tests of inflammation in paediatric appendicitis: a systematic review and meta-analysis.

OBJECTIVE: Possible childhood appendicitis is a common emergency presentation. The exact value of blood tests is debated. This study sought to determine the diagnostic accuracy of four blood tests (white cell count (WCC), neutrophil(count or percentage), C reactive protein (CRP) and/or procalcitonin) for childhood appendicitis. DESIGN: A systematic review and diagnostic meta-analysis. Data sources included MEDLINE, EMBASE, Central, Web of Science searched from inception-March 2022 with reference searching and authors contacted for missing/unclear data. Eligibility criteria was studies reporting 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 commonly presented cut-offs. To provide insight into clinical impact, we present strategies using a hypothetical cohort. RESULTS: 67 studies were included (34 839 children, 13 342 with appendicitis), all in the hospital setting. The most sensitive tests were WCC (≥10 000 cells/µL, 53 studies sensitivity 0.85 (95% CI 0.80 to 0.89)) and absolute neutrophil count (ANC) (≥7500 cells/µL, five studies sensitivity 0.90 (95% CI 0.85 to 0.94)). Combination of WCC or CRP increased sensitivity further(≥10 000 cells/µL or ≥10 mg/L, individual patient data (IPD) of 6 studies, 0.97 (95% CI 0.93 to 0.99)).Applying results to a hypothetical cohort(1000 children with appendicitis symptoms, of whom 400 have appendicitis) 60 and 40 children would be wrongly discharged based solely on WCC and ANC, respectively, 12 with combination of WCC or CRP.The most specific tests were CRP alone (≥50 mg/L, 38 studies, specificity 0.87 (95% CI 0.80 to 0.91)) or combined with WCC (≥10 000 cells/µL and ≥50 mg/L, IPD of six studies, 0.93 (95% CI 0.91 to 0.95)). CONCLUSIONS: The best performing single blood tests for ruling-out paediatric appendicitis are WCC or ANC; with accuracy improved combining WCC and CRP. These tests could be used at the point of care in combination with clinical prediction rules. We provide insight into the best cut-offs for clinical application. PROSPERO REGISTRATION NUMBER: CRD42017080036.