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Symptom or disease? The four circle rule.

Four Circles for innovators in Lean Medicine

Four Circles for innovators in Lean Medicine

Most people with symptoms don’t seek medical advice. Those who choose to make an appointment with a doctor are more likely to have a disease and those who are referred to a hospital specialist are even more likely to have pathology. Lean medicine takes account of Bayes’ theorem that demonstrates this simple truth mathematically.

I like to think of it as ‘the four circles rule’.
This schematic tells us that many people with pathology do not seek medical advice and some don’t even have symptoms. It also tells us that doctors have to find those with pathology from among the many who do seek their advice. Often patients present with a host of problems, so that the four circles become 8, 12, 16 or even 20 different circles, one set for each condition.

My team have applied this principle to study people with bowel symptoms. It is a fact that most people with bowel symptoms do not have pathology, or at least not cancer. Epidemiologists have identified groups of symptoms which when they occur together are most likely to signify pathology. This isn’t always reliable and there are lots of false positives, leading to anxiety among the worried well. On the other hand it is also true that people with pathology may or may not seek medical advice. The latter is especially true of men who find discussing their bowels embarrassing. Sometimes so much so that they don’t mention the diarrhoea or rectal bleeding to anyone, least of all their doctor. The consequences are that in some cases they delay seeking help for potentially life limiting disease until it is too late for curative treatment.

We also know that colorectal cancer is diagnosed in most cases only after the patient has developed symptoms and sought medical advice. Only a minority of cases are diagnosed from among those with no symptoms who have been screened for the disease. Whatever the case the sooner a diagnosis is made the better the chances of successful treatment. Because the symptoms can be so embarrassing and to some extent because some men procrastinate with seeking advice colorectal cancer has a worse prognosis in men.

It’s in situations like these that innovations which are low cost, personalised and offer creative solutions to healthcare problems come into their own. The focus could be to provide opportunities for as many people as possible to get convenient, reliable, personalised information in privacy without necessarily going to a doctor. What’s more such an innovation needs to make life easier for the practitioner and the patient.


  1. […] cases the chance of being diagnosed with cancer, despite the ‘data’ is, thankfully, relatively small. That means that of all those who present with symptoms for the first time, it is the communication […]

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