Abstract
Background
The purpose of using preventative inhaled treatments in cystic fibrosis is to improve health outcomes. Therefore, understanding the relationship between adherence to treatment and health outcome is crucial. Temporal variability, as well as absolute magnitude of adherence affects health outcomes, and there is likely to be a threshold effect in the relationship between adherence and outcomes. We therefore propose a pragmatic algorithm-based clustering method of objective nebulizer adherence data to better understand this relationship, and potentially, to guide clinical decisions.
Methods to cluster adherence data
This clustering method consists of three related steps. The first step is to split adherence data for the previous 12 months into four 3-monthly sections. The second step is to calculate mean adherence for each section and to score the section based on mean adherence. The third step is to aggregate the individual scores to determine the final cluster (“cluster 1” = very low adherence; “cluster 2” = low adherence; “cluster 3” = moderate adherence; “cluster 4” = high adherence), and taking into account adherence trend as represented by sequential individual scores. The individual scores should be displayed along with the final cluster for clinicians to fully understand the adherence data.
Three illustrative cases
We present three cases to illustrate the use of the proposed clustering method.
Conclusion
This pragmatic clustering method can deal with adherence data of variable duration (ie, can be used even if 12 months’ worth of data are unavailable) and can cluster adherence data in real time. Empirical support for some of the clustering parameters is not yet available, but the suggested classifications provide a structure to investigate parameters in future prospective datasets in which there are accurate measurements of nebulizer adherence and health outcomes.
Disclosure
This report is independent research arising from a Doctoral Research Fellowship (Zhe Hui Hoo, DRF-2014-07-092), supported by the National Institute for Health Research. The views expressed in this publication are those of the authors and not necessarily those of the National Health Service, the National Institute for Health Research, or the Department of Health.
Rachael Curley received support from Zambon and Philips Respironics for a parallel research study monitoring inhaled adherence. Martin J Wildman received funding from Zambon and support from Philips Respironics for the same study. This has not had any direct influence on this submitted paper. Martin J Wildman has worked with Pari to carry out studies using the chipped E-flow (e-track). Michael J Campbell reports no conflicts of interest in this work.