When more testing is not better care

Why more tests can mean less clarity

Each test is a question, and every answer carries some chance of error. A test can flag a problem that is not there, called a false positive, or miss one that is, called a false negative. The more tests you have without a clear reason, the more likely it is that one result falls outside its range by chance, and each of those results needs explaining.

Good testing starts from the question. When a doctor knows what you want to find out and what you would do with the answer, a few well chosen tests give a clearer picture than many.

Overdiagnosis

Overdiagnosis is the diagnosis of a condition that would never have caused symptoms or death. It needs a reservoir of silent disease and a test that looks for it, and screening supplies the test [1].

Welch and Black estimated from randomised trials that about 25% of breast cancers found by mammography and about 60% of prostate cancers found by PSA testing were overdiagnosed [1]. People in that position receive treatment, with its side effects, for a cancer that would not have harmed them.

For this reason the UK National Screening Committee does not recommend PSA screening for every man, and names incontinence and erectile dysfunction in men who did not need treatment among the main harms [2].

Incidental findings on scans

An incidental finding is something a scan shows that nobody was looking for. In a review of brain MRI in people without neurological symptoms, one incidental finding was made for every 37 people scanned [3].

A later review of 32 studies, covering 27,643 adults without symptoms, found potentially serious incidental findings in 3.9% of people having brain and body MRI, rising to 12.8% when findings of uncertain importance were included [4]. In the limited data on final diagnoses, 20.5% of the potentially serious findings proved serious [4].

Proving a finding harmless can mean further scans, a biopsy, a specialist opinion and weeks of waiting. Some findings do matter, so the value of a scan depends on agreeing with your doctor beforehand how any finding will be handled.

False alarms and false reassurance

A false positive leads to more tests to rule out a problem you never had. The FDA notes that an abnormal finding on a whole body CT may not be serious and a normal finding may be inaccurate, and that false leads can prompt further, unnecessary testing [5].

Uncertainty has a cost of its own. Waiting weeks for a follow-up scan to clear a finding can be hard, so it is worth deciding before a test whether you would want to hear about findings of uncertain importance.

A normal result has limits too. A test done once in a person without symptoms can miss a problem, so a normal result is no reason to ignore a new symptom later.

How to choose the right tests

Choosing Wisely UK, from the Academy of Medical Royal Colleges, suggests four questions for any test or treatment, known as BRAN [6].

Shared decision making accepts that there is usually more than one reasonable option, including no test or treatment at all [6]. A doctor who knows your history can tell you which tests have good evidence for someone like you.

• What are the benefits of this test for me?
• What are the risks, including a false alarm or a finding that needs follow-up?
• What are the alternatives, such as waiting or a simpler test?
• What happens if I do nothing for now?

When more testing is the right choice

More testing is right when there is a reason for it. New symptoms, a strong family history, a result that needs confirming and a screening test due at your age are all good reasons, and a doctor will not hold back a test you need.

Screening with good evidence is worth having on time. The UK National Screening Committee recommends screening for a small number of adult conditions, including bowel, breast, cervical and lung cancer [7].

If you have chest pain, sudden breathlessness, severe bleeding or signs of a stroke, do not wait for a test. Call 999 in the UK or the local emergency number.

How The Wellness can help

A GP appointment at The Wellness gives you time with a GMC registered doctor to agree what you want to know and which tests would answer it. If you have been offered a test or a scan elsewhere, bring the details and the doctor will tell you what the evidence says for someone like you.

When testing is the right choice, regulated services are delivered through registered partner clinics and accredited laboratories, and a doctor explains every result. For a longer conversation about healthspan and which advanced tests are worth it, the longevity consultation is free and held by video.