Part 4: Evaluating the evidence

Download Part 4: Chapters 10 & 11

Chapter 10: Judging which tests and treatments really work

We are constantly bombarded with health information, and this can make health decisions seem overwhelming. But if you develop a basic understanding of the different types of evidence available to help guide your decisions, the task can seem less daunting. Evidence-based guidelines can provide a useful overview. Systematic reviews of all the randomised controlled trials are the most reliable sources of information, followed by single randomised controlled trials. Other types of studies, such as non-randomised trials and case control studies, are not as reliable. The least reliable forms of evidence are opinions, case reports and anecdotes.

Chapter 11: What makes you sick?

Living near power lines causes cancer. So does eating burnt steak. These are just some of the many claims made about the causes of disease. While randomised controlled trials are the ‘gold standard’ for evaluating the effect of interventions, they cannot be used in all cases. Obviously it would be unethical to randomly allocate people to set up house close to power lines to test the causes of cancer. Observational studies, which follow groups of people rather than testing the effects of an intervention, can provide useful information about causes of disease and risk factors for illnesses. But they also have some limitations.