Temporal trends and practice variation of paediatric diagnostic tests in primary care: retrospective analysis of 14 million tests.

Objective: The primary objective was to investigate temporal trends and between-practice variability of paediatric test use in primary care.
Methods and Analysis: This was a descriptive study of population-based data from Clinical Practice Research Datalink Aurum primary care consultation records from 1 January 2007 to 31 December 2019. Children aged 0-15 who were registered to one of the eligible 1464 general practices and had a diagnostic test code in their clinical record were included. The primary outcome measures were (1) temporal changes in test rates measured by the average annual percent change, stratified by test type, gender, age group and deprivation level and (2) practice variability in test use, measured by the coefficient of variation.
Results: 14 299 598 diagnostic tests were requested over 27.8 million child-years of observation for 2 542 101 children. Overall test use increased by 3.6%/year (95% CI 3.4 to 3.8%) from 399/1000 child-years to 608/1000 child-years, driven by increases in blood tests (8.0%/year, 95% CI 7.7 to 8.4), females aged 11-15 (4.0%/year, 95% CI 3.7 to 4.3), and children from the most socioeconomically deprived group (4.4% /year, 95% CI 4.1 to 4.8). Tests subject to the greatest temporal increases were faecal calprotectin, fractional exhaled nitric oxide and vitamin D. Tests classified as high-use and high-practice variability were iron studies, coeliac testing, vitamin B ₁₂ , folate, and vitamin D.
Conclusions: In this first nationwide study of paediatric test use in primary care, we observed significant temporal increases and practice variability in testing. This reflects inconsistency in practice and diagnosis rates and a scarcity of evidence-based guidance. Increased test use generates more clinical activity with significant resource implications but conversely may improve clinical outcomes. Future research should evaluate whether increased test use and variability are warranted by exploring test indications and test results and directly examine how increased test use impacts on quality of care.
Competing Interests: Competing interests: This project was funded by a grant from the NIHR SPCR grant (Award 624). The funders were not involved in the study design and conduct, data collection and interpretation, or manuscript preparation and approval to submit the manuscript for publication. ETT was supported by a Clarendon scholarship to study for a Doctor of Philosophy (DPhil) at the University of Oxford (2020–23). PG has received grants from the Canadian Institutes of Health Research (CIHR), the Physicians Services Incorporated Foundation and The Hospital for Sick Children. He has received non-financial support from the EBMLive Steering Committee (expenses reimbursed to attend conferences) and the CIHR Institute of Human Development, Child and Youth Health (as a member of the institute advisory board, expenses reimbursed to attend meetings), is a member of the CMAJ Open and BMJ Evidence Based Medicine Editorial Board. RP is partly supported by the NIHR Applied Research Collaboration (ARC) Oxford & Thames Valley, the NIHR Oxford BRC, the NIHR Oxford MedTech and In-Vitro Diagnostics Co-operative (MIC) and the Oxford Martin School. CJH receives funding support from the NIHR School of Primary Care Research. The funders had no role in study design, manuscript submission, or collection, management, analysis, or interpretation of study data. All other authors have no sources of funding to declare.
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