Jonathan consults his doctor regularly and each time he comes to the clinic he expects to go next door for a blood test or X-ray. Like many people he believes that a positive test means he has a specific condition and a negative test implies that all is well. So he has come to conclusion that a doctor who doesn’t order a test is not doing his job.

No test is that good. A ‘positive’ test often requires more investigations or a repeat test to rule out the rabbit being pursued down the proverbial hole. A test is only a useful tool in the hands of the doctor who factored the risk of a specific diagnosis. Therefore a teenager with a severe sore throat, fever and fatigue is likely to have Glandular fever and a positive test is likely to have a high positive predictive value.

On the other hand being tired all the time is more likely to be related to some non-physical cause such as stress, lack of sleep or worry than it is to an under active thyroid gland or anaemia. And yet test ordering is a common outcome in consultations. For example ‘hypothyroidism’ or an under active thyroid gland is thought to be present in 3.8% of the population. The majority of those with the condition are older females. In a study where doctors were given feedback about their test ordering Thyroid function tests were the commonest test ordered with up to 21 per 1000 patients having the test. When doctors were offered feedback about test ordering the number of patients in the practices receiving the feedback reduced but not significantly. Australian experts advise that:

Signs and symptoms of hypothyroidism may vary depending on patient characteristics and the severity of dysfunction. Classic symptoms include fatigue, weight gain, cold intolerance, arthralgia, constipation, menorrhagia, irregular menstrual cycles, and dry skin and hair. Physical signs include coarse skin and hair, bradycardia and goitre but these may be absent in mild hypothyroidism.

NPS https://www.nps.org.au/news/thyroid-disease-challenges-in-primary-care

However they conclude that:

Requests for thyroid tests are increasing, although in many cases clinical need is not evident.

NPS https://www.nps.org.au/news/thyroid-disease-challenges-in-primary-care

I offer some more thoughts on video.

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