Thursday, March 20, 2014

Why do doctors order so many tests ?

One of the things doctors do most commonly is order tests. The uncharitable explanation for why they do so many tests is for financial reasons. It’s an open secret that the diagnostic laboratories and scan centers often give doctors a kickback (commission ) on each test, which means that it makes financial sense for them to do lots of tests . However, there are lots of ethical doctors who do not get kickbacks , and yet they order lots of tests. Why is this so ?

One of the reasons is a very common psychological fallacy most of us are fooled by. We often believe that the more the data we have , the more accurate will be our diagnosis . Doctor confuse more information with more accuracy.

Actually, this seems to make a logical sense . After all, isn’t it common sense that more information should give lead to more accuracy ? This is why when doctors encounter patients with a complex problem, they order more tests to get more information. They hope that the test results will give them more insight into the right diagnosis.

However, psychologists have shown that more information does not always improve accuracy . In reality, more data has the pernicious side effect of increasing the confidence levels of the doctor in his diagnosis. This is not a problem which is unique to doctors - it actually applies to experts in all fields , including financial advisors. Because lots of doctors are not aware of this common cognitive bias , they over-order tests when they are stumped, in order to try to improve the accuracy of their diagnosis, without realizing that they are not doing much good !

Another reason why doctors order tests is because this is what patients demand and expect ! Most patients are no longer satisfied by a  clinical examination ( even though this is far more valuable than any number of tests ! ) Today’s patients seem to have more confidence in scans and computer printouts. They need technology in order to be satisfied that the doctor has done a good job - and sometimes it is just to keep the patient satisfied that the doctor orders tests. Patients will often question a doctor’s efficiency if he does not do tests – and some feel the doctor was not thorough or careful if he did not order tests !

This is ironic , because only a very confident and competent doctor will actually refuse to order tests. A dirty little secret is that many of these tests can actually be harmful , because they lead to a lot of unnecessary overtreatment . More is not always better !  However , patients are not sophisticated to question the doctor. The key question they need to learn to ask when the doctor orders a test is simple – How will this change my treatment ?

Because they do not do so, the explosion of new technology means that the number of tests a doctor can order has grown exponentially ! Also, when doctor attend conferences, they want to learn “what’s hot and what’s new”. They are seduced by attractively produced presentations, which tom-tom the accuracy and efficiency of the newest tests – and no one bothers to highlight their limitations, because these key note speakers are usually sponsored by the company which is selling the tests.

Let’s look critically at the newest test which is being marketed for IVF patients today. This is called the endometrial receptivity assay, or the ERA. This uses genetic markers as an endometrial function test , to test if the endometrium will allow an embryo to implant. This is a very new,  sophisticated test, which is very expensive and is offered by only one company so far. Since failed embryo implantation is such a distressing problems, IVF specialists are very happy to order this tests for patients who have failed IVF cycles. However, because doctors understand precious little about genetics, they end up fooling  themselves - and their patients. Thanks to a lot of slick marketing, with tons of genetic gobbledygook which doctors don’t understand, it’s surprisingly easy to take doctors for a ride !

Because doctors want to be “one-up” on other doctors, they are happy to order the “latest tests” – which are often much more expensive, because they are new. This newness  also means they are much more unreliable, because we don’t have enough clinical experience with them !

Ironically, patients don’t seem to mind paying for all these unnecessary tests. In fact, most of them are quite happy when the test results come back as normal, because they naively believe that these means they are fine!  They don’t seem to consider the money spent on the test as a waste ! Actually, the purpose of tests when used judiciously is to confirm or rule out a clinical diagnosis, based on the doctor’s clinical examination. It cannot be a hunting expedition, where the doctor uses a “spray and pray” approach to try to find an abnormality , which may be of no clinical importance !

However, doctors, like most people , generally believe that the more information they have the better their decisions will be . This is why they often pursue information that is inconsequential to their final decisions . However, the reality is that more knowledge can reduce the accuracy of prediction of uncertain outcomes , and simultaneously increase the doctor’s confidence in their  incorrect  predictions.  As the Nobel laureate Daniel Kahneman pointed out, "Overconfident professionals sincerely believe they have expertise, act as experts and look like experts. You will have to struggle to remind yourself that they may be in the grip of an illusion." Doctors need to learn from his wise words - “Be honest with yourselves! Admit what you don’t know!”

A common cognitive bias doctors suffer from is the “illusion of validity” . How do patients distinguish the justified confidence of experts from the sincere overconfidence of professionals who do not know they are out of their depth? Overconfidence arises because people are often blind to their own blindness.
The bottom line which doctors need to ask themselves before ordering a test is – how will this change the patient’s treatment options ? Let’s not lose sight of this in our enthusiasm for ordering  tests ! ( And if the doctor does not ask this question, the patient needs to learn to do so !)

Confused about why your IVF doctor is ordering so many tests ? Please send me your medical details by filling in the form at so that I can guide you better !

1 comment:

  1. I would like to use the cartoon with caption "Off Hand, I'd say you're suffering from an arrow through your head, but just to play it safe, I'm ordering a bunch of tests." in a medical journal article with 700 hard copies printed. Could you tell who the cartoon belongs to? I need to contact them for copyright authorization.
    Thank you.


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