Variation in lung function as a marker of adherence to oral and inhaled medication in cystic fibrosis

Abstract

The aim of this study was to characterise adherence in an adult population with cystic fibrosis (CF) and to investigate if variation in lung function was a predictor of adherence to treatment.The adherence of patients aged ≥16 years from an adult CF centre was measured by medication possession ratio (MPR) and self-report. Patients were assigned to one of three adherence categories (<50%, 50 to <80%, ≥80%) by their composite score (MPR). Ordinal regression was used to identify predictors of adherence, including coefficient variation measures for forced expiratory volume in 1 s (FEV), weight and C-reactive protein concentration, measured from 6 months and 12 months before baseline.MPR data for 106 of 249 patients (mean age 29.8±9.2 years) was retrieved, indicating a mean adherence of 63%. The coefficient of variation for FEV was inversely related to adherence and was a univariate predictor of adherence (6 months: OR 0.92, 95% CI 0.87-0.98, p=0.005; 12 months: OR 0.94, 95% CI 0.93-0.99, p=0.03) and remained significant in the final models. The coefficient of variation of weight and C-reactive protein were not predictive of adherence.The coefficient of variation of FEV was identified as an objective predictor of adherence. Further evaluation of this potential marker of adherence is now required.

<p>Adherence to long-term therapies in cystic fibrosis: a French cross-sectional study linking prescribing, dispensing, and hospitalization data</p>

“…Adherence also varied between pharmaceutical forms: patients were less adherent to inhaled therapies than oral medications, which is in agreement with previous findings 11,26. One aspect that could explain this is the more complex management and time-consuming use of inhaled medications, such as inhalation technique, nebulization time, or cleaning devices 24,27.…”

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“…There are concerns regarding the resource requirements to implement comprehensive encounter‐based data collection, but a previous modelling exercise using worst case scenario estimates did suggest that 75 minutes of data entry session per week would be adequate for a medium‐sized CF centre to implement this, which is equivalent to a cost of approximately £4 per patient per year . Some adult CF centres in the United Kingdom, such as Leeds and Sheffield, have already implemented encounter‐based FEV 1 data collection via the use of integrated electronic care records, and the CFHealthHub platform (ISRCTN55504164) now in use in 80% of the UK adult CF centres also offers a facility for encounter‐based FEV 1 data capture.…”

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“…This is hard to quantify, but in our registry weight fluctuations of 2-3 kg are very common. White et al [15] report a coefficient of variation of~11% for FEV 1 .…”