Dr Liza Macdonald FRCR MA

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Discussion about Medical Risks

  Getting The Best out of Your Doctor




Discussion about Medical Risks


Many aspects of medical care carry risks. One of the duties of your doctor is to provide a clear explanation and help you understand and weigh up the risks for yourself. Helping you understand any risks and discussing what is important to you are essential.

The concept of risk however can be complex and difficult to describe. In order to be useful for you information needs to be relevant both in a personal and a medical sense.

The idea of risk contains two distinct parts: first, some kind of unwanted outcome (e.g. risk of side-effects with medication or risks of infection with an operation) and secondly some uncertainty about the likelihood of that unwanted outcome. In thinking about any risks of treatment likely to affect yourself you may need to consider things in several stages.

1. What are the unwanted outcomes? Are there lots or just a few? Are they just at the level of an irritation or something more threatening?

2. How permanent are any of these unwanted outcomes? Will they improve with time or not?

3. When will the unwanted outcome occur? Will it start straight away or come on gradually in stages over time. If they do come on slowly will this give your doctor time to take an alternative approach such as reducing the dose or changing the medication?

4. How likely is it to happen at all? Does it result from a single or multiple exposures with accumulating risk? For example does it increase with each course of chemotherapy?

5. How much does this unwanted outcome matter to you as an individual? If you work in the public eye for example losing your hair may be more important than for someone who works from home. (but not worth losing your life for!)

Many of your responses to these questions may be highly individual. Often the main calculation is whether to accept significant risk now for possible future benefit (e.g. side effects of proposed treatment with a view to increased survival or quality of life).

Thinking about Probability

Describing a risk requires a qualitative description (how it would feel, exactly what could happen, how long it would last) but the probability of that risk can be described in several ways. A risk may be described simply as "rare" or "common" or alternatively may be expressed as a percentage of possibility. Some people prefer general descriptions while others find statistics more helpful. Numbers can however be misleading too. A 10% mortality rate may sound quite different from a 90% survival rate although the information is essentially the same.

Most people find it easier to understand a risk described as a "one in ten chance" or a "one in a thousand chance" rather than more difficult percentages.

Common Errors in Risk Interpretation

Doctors have observed that people often perceive themselves as relatively invulnerable and therefore less likely than others to experience an adverse effect. Some may give excessive weight to risks they have heard of in the media or from friends. Some people may be over-confident of the extent and accuracy of their own medical knowledge. They think they already know what risks are entailed and often downplay them.

In addition it appears that "new" risks such as SARS or the Zika virus seem to be given more weight than longer standing threats (hepatitis or malaria). The true perception of risk, as a result, can be distorted.

Reconciling the Average and the Individual

Perhaps the greatest challenge in discussing risk is to convey effectively an understanding of how the "average" result may impact on the individual. The average, derived from an analysis of a patient population, (i.e. a whole lot of people with the same illness), may for example suggest a 5% chance of a complication, a relatively low risk. For any individual patient however if that complication occurs it is an all or nothing phenomenon i.e. 100% for them.

Readily Accessible Ways to look at Risk

Many people find graphic displays more readily understandable than complicated numbers. Looking at a graph or a block diagram can have more impact than words alone. Alternatively most people have some idea about common risks in everyday life and have developed some experience of how to evaluate them. Comparing possible medical risks to these wider risks may be helpful and make medical risks more understandable to the rest of us. Some common risks in the United Kingdom were recently quoted in the Sunday Times (Jonathon Leake 27.04.03)

Causes of death in the United Kingdom 2001 i.e. Risks

Cancer deaths per year in the United Kingdom190,000.
Heart disease deaths per year132,000.
Deaths from influenza4000.
Road traffic accident deaths3400.
Murders per year1050.
Deaths from Aids and HIV155.

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