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 primary care consultation records from January 1, 2007, to December 31, 2019. Children aged 0 to 15 who were registered to one of the 1,464 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 (AAPC), stratified by test type, gender, age group, and deprivation level and 2) practice variability in test use, measured by the coefficient of variation (CoV).

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 399/1,000-child-years to 608/1,000 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 the most socioeconomically deprived group (4.4%/year, 95% CI 4.1 to 4.8). Tests subject to the greatest temporal increases were fecal calprotectin, fractional exhaled nitric oxide (FeNO), and vitamin D. Tests classified as high use and high practice variability were iron studies, vitamin D, vitamin B12, folate, and coeliac testing.

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 is warranted by exploring test indications and test results, and directly examine how increased test use impacts on quality of care.

What is already known on this topic Previous research has shown that test use in adults within UK primary care sharply increased since 2000 and that there is a high degree of practice variation in test use. To date, no population-based studies have analysed paediatric test use in this setting.

What this study adds In England between 2007 and 2019, diagnostic test use increased by 4% per year, from 399 tests/1,000 child-years to 608 tests/1000-child years. Test increases were driven blood tests, especially in females aged 11-15 years of age, and children in the most deprived socioeconomic group. Specific tests that increased by the greatest margin include faecal calprotectin, fractional exhaled nitric oxide (FeNO), and vitamin D testing. Tests subject to the greatest practice variation by 2019 were FeNO, hearing tests, and vitamin D levels.

How this study might affect research, practice or policy Variability in test use highlights a lack of standardised guidance and evidence in pediatric diagnostics, which has significant implications for downstream diagnostic activity, treatment, referrals and healthcare costs.

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 nonfinancial 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.

https://github.com/elizabethtthomas/cprd-paediatric-tests

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.

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

The protocol was approved via the Clinical Practice Research Datalink Research Data Governance process (study reference 22_001998).

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

Yes