Earlier is not necessarily better

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Key points

  • Earlier diagnosis does not necessarily lead to better outcomes; sometimes it makes matters worse
  • Screening programmes should only be introduced on the basis of sound evidence about their effects
  • Not introducing a screening programme can be the best choice
  • People invited for screening need balanced information
  • The benefits of screening are often oversold
  • The harms of screening are often downplayed or ignored
  • Good communication about the benefits, harms, and risks of screening is essential

Introduction

In the previous sections we have shown how treatments that are inadequately tested can cause serious harm. Here we turn our attention to screening apparently well people for early signs of illness. Screening sounds so sensible – how better to ward off serious consequences of disease and stay healthy? While screening is helpful for several conditions, screening can harm as well as help.

From person to patient

Screening will inevitably turn some people who test ‘positive’ into patients – a transformation not to be undertaken lightly.

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In this section we draw on various disease examples to show why earlier diagnosis can be but is not always better; why many types of screening are of no, or uncertain, benefit; and how the benefits of screening have often been oversold and the harms downplayed or ignored. Screening healthy people should never be undertaken lightly:  there are always important downsides that should make us cautious. Screening is a medical intervention. Not only that, the offer of screening is in itself an intervention. Even someone who chooses to decline screening will be left with a nagging doubt about whether they have made the ‘right’ decision – that is human nature. Not being offered screening in the first place is very different.

At best, screening should only be offered to the healthy people it seeks to reassure or treat if there is sound evidence that: (a) it will do more good than harm at an affordable cost; and (b) it will be delivered as part of a good quality and well-run programme.[1]

Screening is much more than a ‘one-off’ test. People invited for screening need sufficient unbiased, relevant information so that they can decide whether to accept the offer or not – that is, they need to know what they are letting themselves in for.[2]

One way of thinking about screening is like this:

Screening = a test plus an effective management strategy

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