Intended for healthcare professionals

Letters New diagnostic tests: more harm than good

All tests can sometimes cause more harm than good

BMJ 2017; 358 doi: (Published 01 September 2017) Cite this as: BMJ 2017;358:j4070
  1. Jessica C Watson, GP and NIHR doctoral research fellow
  1. Canynge Hall, University of Bristol, Bristol BS8 2PS, UK
  1. jessica.watson{at}

Hofmann and Welch warn of the downsides of diagnostic tests.1 “All screening programmes do harm . . . [but] some do more good than harm at a reasonable cost.”2 This provocative statement is arguably true of any test, not just screening or new diagnostic tests. The challenge for clinicians is to share decisions with patients—choosing the right test for the right patient at the right time.

Inflammatory marker tests, such as C reactive protein, are simple, inexpensive, and commonly used in both primary and secondary care.3 When we interviewed GPs about their use of inflammatory marker blood tests in primary care, all doctors mentioned potential harms as well as benefits of testing.4 These could be divided into several categories; harms of the test itself, workload and financial costs, medicalisation of a patient’s problem, patient anxiety, downstream costs, and harms of overdiagnosis.

Harms from the test itself are often overlooked and include cost of patients’ time off work, needle phobia, bruising, and vasovegal syncopy. One GP described the psychological cost: “There is always this pass or fail thing . . . because it’s looking inside your body, and there might be something wrong there. It’s not something one should do lightly.”

In UK primary care, rising workload is a major concern,5 and many GPs in our study thought that time spent dealing with pathology results was often inefficient or wasteful. Medicalisation can occur when tests cause “somatic fixation,”6 with patients or clinicians focusing only on the biomedical aspects of complex illness. Patient anxiety is perhaps the hardest to capture yet most important harm of unnecessary testing. Anecdotal stories, such as Fran’s story,7 can be powerful, but the overall cost is hard to estimate. We need further research into the benefits and harms of diagnostic tests, not just for new diagnostic tests, but also for many commonly used “routine” tests.

Overuse of diagnostic tests might reflect a societal culture of increasing risk aversion and rising medical litigation, as well as a culture in medicine that “evinces a deep rooted unwillingness to acknowledge and embrace uncertainty.”8 Technological advances and new tests provide ever more information, yet without wisdom9 we risk making well people sick, rather than sick people well.


  • Competing interests: None declared.


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