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Patients ‘overestimated statin benefit when lacking numerical information’

Patients tended to overestimate the benefits of statin treatment when given patient leaflets that only included text-based rather than numerical information, according to a study at one GP practice.

Researchers interviewed 21 patients who were given a prescription for simvastatin and one of three enhanced patient information leaflets, each including extra information on the benefits of treatment.

One of the leaflets gave the extra information in a textual statement, while the other two gave the absolute benefits in numerical terms – one as a number needed to treat (NNT) and one as a natural frequency.

The researchers reported in BMJ Open that patients viewed the benefit information as ‘helpful and useful to know’ and that while the ‘numerical information provided better clarity’, most preferred the textual information for example because it was ‘easy to read’.

However, they also found that participants ‘frequently overestimated the benefits of their medicine and when presented with numerical information about simvastatin this provoked surprise and disappointment’.

Participants largely preferred the natural frequency format, rather than the NNT information which ‘appeared to cause a great deal of confusion’.

The researchers concluded: ‘This study suggests that currently in the absence of the provision of numerical information about benefits many patients overestimate the benefit of their statins.’

However they added that providing numerical information is ’problematic as many people do not understand or value this information’.

Use of patient information leaflets to convey treatment benefits 

Academics from York and Leeds universities, in collaboration with the MHRA,  hypothesised that as patient information leaflets are ‘the only regulated written information a patient receives with their medicines’, they could therefore be ‘part of the solution’ to providing patients with better information about the pros as well as cons of a treatment.

They gave patients leaflets designed to look like patient information leaflets available with UK medicines and using the hypothetical name ‘Rebastatin’ in place of simvastatin

The extra information on benefits was given as:

  • Text: Rebastatin can reduce the chance of you having a heart attack or stroke. It does this by lowering levels of cholesterol and triglycerides in your blood
  • NNT: If 17 people take Rebastatin over the next 5 years, one of them will be prevented from having a heart attack or stroke
  • Natural frequency: In 100 people like you who do not take this medicine, 28 will have a heart attack or stroke. But if they all take Rebastin over the next 5 years, 22 will have a heart attack or stroke.

BMJ Open 2016; available online 2 December



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