How do you know your doctor has made the right diagnosis? According to new research, more than 20% of patients sent for a second opinion will indeed have had an incorrect first diagnosis. And if this study, in the Journal of Evaluation in Clinical Practice, sounds scary, then it only echoes a report in 2015 from the National Academy of Medicine in the US saying that most people will have at least one incorrect or late diagnosis.

The solution

In this latest study, researchers compared the diagnoses of 286 patients before and after their referral to the Mayo Clinic in Minnesota. They found that one in five patients ended up with a diagnosis very different from the one their primary care doctors (more or less equivalent to GPs in the UK) put on their referral form. Professor James M Naessens in the Division of Health Care Policy and Research at the Mayo Clinic says that not every condition needed a second opinion. “However, with the diagnosis of a serious condition, if the condition is not responding as expected, it may be valuable to get another perspective,” he says.

A UK study of 1,000 patients who died in 10 hospitals found that 5.2% of deaths might have been preventable, of which just less than a third had a wrong diagnosis. It’s the common conditions such as pneumonia, heart failure, acute kidney failure and cancer that are most often missed.

Diagnoses start with a doctor taking a history, examining a patient and coming up with a hypothesis. This hypothesis may be proved or changed by tests, more examinations and sometimes new symptoms emerging. And patients in the Mayo Clinic study often had vague diagnoses in the first place. An initial diagnosis of weight loss – not a disease in itself – turned out to be a lymphoma, while someone with anaemia, which can caused by a number of different diseases, ended up with a diagnosis of autoimmune hepatitis.

If you aren’t sure about a diagnosis your GP has given you, you can ask them to explain why they have ruled out a condition you’re particularly worried about. If you’re still not convinced, they should refer you to a colleague. If you want a second opinion after a hospital consultation, you can also ask the doctor to explain their thinking to you. Or you can tell your GP, who can ring the hospital and ask for more details. Your GP can refer you to another consultant, but if this goes through a central referral management system, it can take a while. Your GP will tell the consultant of your previous referral and include any test results. Doctors are generally fine about second opinions – they don’t want dissatisfied patients and don’t want to miss what could be the right diagnoses.