Evidence-based medicine

The second step: Evaluating the information

When making informed decisions about medical treatments, the first step is to gather reliable information. The second step involves assessing the information and weighing the pros and cons. The following examples and questions may help you do this.

Let's say, two men called Peter and Carl have been told by their doctors that they have hypertension (high blood pressure). And they have both been given a prescription for hypertension medication.

  • Carl is 50 years old. He is 1.75 meters tall, weighs 80 kilograms (about 5 foot 9 and about 176 pounds), and is healthy. But his blood pressure is a bit too high, at 145 over 92 mmHg.
  • Peter is also 50 years old. He is the same height as Carl, but weighs 10 kilograms (around 22 pounds) more. His blood pressure is 160 over 100 mmHg. And he smokes.

Neither of them really likes the idea of having to take tablets every day from now on. They have to decide: Do I want to take medication for hypertension or not?

Question 1: What will happen if I just do nothing, and wait and see?

To answer this question, the information they have gathered about the expected course of the disease is important. This includes information on the consequences associated with a particular disease or diagnosis. Doctors call this the prognosis. To have an idea of what consequences a disease can have and how frequent they are, information taken from good-quality studies is needed.

Carl and Peter

Hypertension is a risk factor for cardiovascular diseases like strokes or heart attacks. The risk of having a heart attack can be estimated:

  • Carl has a 4% risk of having a heart attack within the next ten years if his blood pressure stays the same. In other words, 4 out of every 100 men like Carl will have a heart attack. Or, seen from a different angle: 96 out of every 100 men whose health is similar to Carl's will not have a heart attack, even if they do not have any treatment.
  • Peter has a 23% risk of having a heart attack within the next ten years because his blood pressure is much higher and he has other risk factors too. Out of every 100 men like Peter, 23 will have a heart attack and 77 will not, assuming they continue to smoke and don't make any other changes affecting their individual risks.

Knowing your own prognosis might then be enough to base a decision on: You may decide not to have treatment because the condition doesn't worry you much – or you may decide to have treatment because you want to feel safer and do something about it.

Question 2: What can I do about it?

Next it's important to get an overview of the different things you can do to try to change a poor prognosis. You'll have to find out what further diagnostic tests might be done and what the treatment options are.

You won't always have as many options as the two men in our example: When it comes to high blood pressure, there are quite a lot of options, ranging from lifestyle changes to many different medications.

Question 3: What are the advantages and disadvantages of the treatment options?

This question concerns a treatment's benefits and harms, and what will change if you do something rather than just waiting and seeing:

  • What effect can I expect the treatment to have?
  • When will the treatment start working?
  • How long will the effect last?
  • How many people benefit from this treatment?
  • What are the possible side effects?
  • How many people are harmed by this treatment?
  • What does the treatment involve in terms of expenses, time, hospital stays and having to do without other things?

Carl and Peter

The following comparison illustrates how the same treatment with drugs for high blood pressure would have a far greater benefit for Peter than it would for Carl.

  • The advantage of the treatment is that certain drugs can lower the risk of cardiovascular disease.
  • But the treatment also has disadvantages: You have to remember to take the drugs every day, you have to go to the doctor regularly, and you may have to pay money out-of-pocket at the pharmacy. Depending on the type of medication, there is a risk of side effects such as coughing, headaches or edema (fluid retention).

To weigh the advantages and disadvantages, you also need to have information on the frequency of certain events. The table below gives an example of this for treatment using a diuretic hypertension medication.

Because Carl's and Peter's risk of a heart attack are different, the possible benefits of treatment are quite different too: 1 out of every 100 men like Carl will be spared a heart attack over the next ten years if they take the medication, compared to 7 out of 100 men like Peter.

Table: Carl's risk of having a heart attack in the next ten years
  Without medication

With medication

Difference
Risk of having a heart attack

4 out of 100

3 out of 100

1 out of 100

Risk of stopping treatment due to side effects

7 out of 100

7 out of 100

Table: Peter's risk of having a heart attack in the next ten years
 

Without medication

With medication

Difference

Risk of having a heart attack

23 out of 100

16 out of 100

7 out of 100

Risk of stopping treatment due to adverse effects

7 out of 100

7 out of 100

Question 4: How do I weigh the pros and cons of the different treatments in my individual case?

Scientific research alone isn't able to provide an answer to this question. From this point on the answers will be different for different people: No two people will worry the same amount about the same risk. How you feel about the disadvantages and side effects of a treatment will depend on your individual judgment.

If you'd like to benefit from a treatment, you'll usually have to accept some side effects too. But side effects will typically affect only some – not all – people. If you start to experience very unpleasant side effects, you can usually make them go away again by stopping the treatment. Side effects that cause lasting damage are rare.

Carl and Peter

We won't say what the men in our example decide to do. One of the men might turn down treatment because he doesn't think the potential benefits of the medication are worth taking it over many years. Or he might want to try a different treatment and seek information about other options first. The other man might be so busy with work or family obligations that taking medication seems the best choice for now, and he may consider other treatments later.

Question 5: Do I feel informed enough to make a decision?

You might feel that the information you have collected and considered is still not enough to base a decision on. There may be something else important to you that you haven't yet been able to consider. Then it isn't too late to go back and specifically look for the information you need.

Or you could talk to your doctor again. You can also consult another doctor to help you feel more sure about things.

Self-help groups and information centers are another possibility.

It's also important not to feel pressured. Especially when it comes to chronic diseases, screening tests or preventive care, you can often take your time. Or you could make a tentative decision at first, and then reconsider it whenever you like.