GPs do too many diagnostic tests – but we can take a more rational approach

GP locum Dr Edoardo Cervoni calls for a more rational approach to diagnostic testing in primary care

The overuse of diagnostic tests in primary care, particularly those related to nutrients like folic acid, vitamin B12, and zinc, is well-documented in literature.¹ The primary driver behind this trend often lies in a ‘better safe than sorry’ mindset, coupled with a growing emphasis on preventive medicine. However, the evidence supporting routine broad-spectrum testing is weak when there are no clear clinical indications.

For instance, research has highlighted that indiscriminate testing of vitamin D, folic acid, and vitamin B12 in patients without specific risk factors or clear symptoms – such as anaemia or neurological indicators – is generally unnecessary and may contribute to healthcare costs and patient anxiety.^2,3 The Royal College of Pathologists, in alignment with the Choosing Wisely initiative, recommends against testing for these nutrients outside of established guidelines, such as in cases of fatigue or other non-specific symptoms.

The downstream impact of over-testing is multifaceted. When a test result shows a borderline abnormality, it often leads to further unnecessary testing or treatments, a phenomenon known as the ‘cascade effect’. This cascade can stem from a variety of sources, including the ‘better safe than sorry’ mindset and a growing emphasis on preventive medicine. Additionally, non-GP providers, hospital discharge recommendations for follow-up on borderline test results, and requests driven by patient demand also contribute to increased testing frequency.³

Further, clinical guidelines may suggest routine testing as part of chronic disease management, even in the absence of significant new symptoms, amplifying the risk of over-testing. As a result, patients often undergo repeat blood tests, are prescribed supplements they don’t need, or are referred to specialists unnecessarily. These actions drive up healthcare costs and expose patients to risks of overtreatment, such as supplement-induced toxicity, heightened anxiety, and potential complications from unnecessary procedures.⁴

Audit data from primary care practices reveal that a significant proportion of nutrient-related tests, including those for folic acid, vitamin B12, and zinc, do not significantly impact clinical management, instead contributing to a cycle of repeat consultations where the initial clinician may not even be involved. For instance, recent data from our PCN indicated that over half of zinc and vitamin B12 tests performed on patients with vague symptoms, such as fatigue, did not result in clinically meaningful actions.

This lack of continuity exacerbates the problem, as clinicians unfamiliar with the patient’s initial presentation may misinterpret isolated abnormal results, leading to further unnecessary interventions. Moreover, the increasing reliance on electronic health records with automated test-ordering templates can inadvertently promote over-testing, as clinicians may select broad panels without critically assessing the need for each test. As discussed in my recent study on zinc testing and its limited role in diagnosing asthenia, such practices risk over-testing without clear benefit.⁵

Promoting a clinically evidenced approach to more streamlined testing

To address these issues, I propose several initiatives aimed at rationalising diagnostic testing in primary care:

Implementing decision support tools: Integrating clinical decision support tools within EHR systems can help guide clinicians on when specific tests are truly indicated. These tools can provide real-time feedback based on current guidelines, helping to curb the automatic ordering of broad panels.

Education and training: Continuous professional development programmes should emphasise the principles of high-value care, focusing on the appropriate use of diagnostic tests. Case-based learning could illustrate scenarios where limited testing leads to better outcomes, reinforcing the importance of targeted investigations.

Audit and feedback mechanisms: Regular audits of test ordering patterns within practices, coupled with feedback sessions, can highlight areas where over-testing occurs. Sharing these findings with clinicians can foster a culture of critical reflection and improvement.

Streamlining follow-up processes: Ensuring that the clinician who orders a test is also responsible for follow-up can enhance continuity of care and improve decision-making. This approach reduces the risk of misinterpretation of results by a second clinician who lacks context.

Examples of clinical scenarios for streamlined testing

Vitamin B12 testing: Rather than testing patients without clear indications, B12 testing should be reserved for those presenting with specific clinical signs, such as macrocytic anaemia or neurological symptoms like peripheral neuropathy. This approach aligns with evidence-based guidelines, reducing unnecessary testing often prompted by vague symptoms such as fatigue, which may not reliably indicate B12 deficiency.

Folic acid levels: Testing should be limited to patients with clinical signs suggestive of deficiency, such as unexplained anaemia or in specific populations at risk (eg, pregnant women or those with malabsorption syndromes).

Zinc testing: Zinc levels should only be assessed in patients with symptoms like unexplained alopecia, delayed wound healing, or taste abnormalities, rather than being included in a broad panel for vague symptoms.

By adopting these initiatives and refining our approach to testing, we can minimise unnecessary interventions, reduce healthcare costs, and, most importantly, enhance the quality of care provided to our patients.

This approach will encourage more thoughtful, evidence-based decision-making in primary care, ultimately benefiting both patients and the healthcare system as a whole.

Dr Edoardo Cervoni is a GP locum in Merseyside

Further reading

Choosing Wisely: An Initiative of the ABIM Foundation

Foy R, Skrypak M, Alderson S et al. Audit and feedback mechanisms in primary care. BMJ 2020;368:m213   

References

1. Müskens J, Kool R, van Dulmen S et al. Overuse of diagnostic testing in healthcare: a systematic review. BMJ Qual Saf 2022;31(1):54-63  
2. Singer A, McChesney C. Reduce unnecessary routine vitamin D testing. Can Fam Physician 2023;69(9):620-622
3. Feldman L. Choosing Wisely®: Things we do for no reason. J Hosp Med 2015;10(10):696
4. Woodford H, Barrett S, Pattman S. Vitamin D: too much testing and treating? Clin Med 2018 Jun;18(3):196-200
5. Cervoni, E. The role of zinc testing in diagnosing asthenia: a critical evaluation of clinical practices and gender differences. Authorea; Preprint: published 9 September 2024