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Accurate reporting of adherence to inhaled therapies in adults with cystic fibrosis: methods to calculate normative adherence

  • Researchers

    Zhe Hui Hoo, Rachael Curley, Michael J Campbell, Stephen J Walters, Daniel Hind, Martin J Wildman

  • Place of research

    University of Sheffield and Sheffield Adult Cystic Fibrosis Centre, Northern General Hospital, Sheffield, UK.

  • Publication

    Patient preference and adherence, May 2016

  • Subjects

  • Can the reporting of adherence to treatment be standardised?

  • Why is this important?

    There is a plethora of effective treatments that maintain lung health and prevent exacerbations in CF.
    Understanding how these treatments are used and adhered to would be important in supporting the care of people with CF. For example, if someone has declining lung function but is struggling to use twice daily nebulised Tobramycin, switching to thrice daily Aztreonam does not address the root cause of the problem and is hence unlikely to work.
    It is also important to be able to compare the medication adherence rates between different specialist CF centres. The centres with the best medication adherence should be recognised as centres of excellence for other centres to learn from. When making these types of comparisons, it is crucial to compare like-for-like. At present, medication adherence is generally measured as a fraction between how much medication is used and the agreed treatment. That means it is possible for people to have high adherence simply by striking an agreement to be on very little maintenance treatment. An extreme example would be someone has an adherence of 200% simply by using 2 nebulisers in a year if the “agreed treatment” is 1 nebuliser per year (which would be inadequate to maintain lung health). To understand how well a centre is able to support adherence, the effectiveness of the prescribed treatments must also be taken into account.
    There is now wide-spread technology to accurately capture nebuliser adherence data with intelligent machines such as the I-neb. Yet, the potential to harness those data to guide treatment management or to compare the quality of different specialist CF centres would be limited unless there are methods to analyse and report adherence in a way that reflects treatment effectiveness.

  • What did you do?

    We therefore proposed methods to standardise the reporting of nebuliser adherence among people with CF which will take into account treatment effectiveness.
    Treatment adherence is reported as a fraction because any number alone is insufficient to fully describe adherence. For example, a person using 350 nebulisers per year would have high adherence if he / she only needs 365 nebulisers per year, but low adherence if he / she needs 1095 nebulisers per year. A fraction consists of two numbers – one on the top (the ‘numerator’) and one on the bottom (the ‘denominator’). We described simple adjustments that can be made to the adherence data (the ‘numerator’) and to the target treatment (the denominator) to obtain an adherence fraction that reflects treatment effectiveness.

  • What did you find?

    The two main recommendations that we made are to impose 100% as a limit for daily adherence (so that excess treatments on certain days do not artificially inflate the adherence rates) and to set the treatment targets based on the clinical characteristics of a person with CF (so that adherence figure reflects treatment effectiveness). We also proposed some other more detailed adjustments that can improve the accuracy of reported adherence rate.
    We provided justifications and evidence to support our recommendations.

  • What does this mean and reasons for caution?

    There are many potential methods to adjust adherence data and target treatments. At present, it is uncertain which methods are most robust. It is therefore important to test these methods with a suitably large dataset to determine the optimal methods for doing the adjustments.

  • What's next?

    We are analysing the adherence dataset from adults with CF in Sheffield to understand the impact of our proposed adjustments on our centre-level adherence rate. Further work will include performing the same analysis on a much larger dataset, which can be obtained during a randomised control trial of systematic adherence intervention (ACtiF, further information - which will be conducted in 20 adult specialist CF centres across the UK. The ultimate aim is working towards understanding how much adherence is enough to sustain lung health among people with CF.