BACKGROUND: Adherence to pulmonary medication is pivotal in delaying the progression of lung disease in cystic fibrosis (CF). Further exploring the consequences of poor adherence and its impact on disease severity may be valuable to personalize CF treatment strategy.
AIM: To evaluate indicators of disease severity among children and adults with CF and investigate which of them are related to pulmonary medication adherence.
METHODS: This is a retrospective cohort study. Data of children and adults followed up in one pediatric and one adult CF Unit were evaluated over 4 years. Disease severity was assessed by measuring body mass index (BMI), lung function, history of pulmonary exacerbations, and medication complexity. Adherence was assessed by calculating a 12-month medication possession ratio (MPR) for each pulmonary medication and then averaged for a composite MPR (cMPR) for each patient. Regression analysis was performed to explore the association of adherence with disease severity.
RESULTS: Ninety-five patients were included in our study, 52 children and 43 adults. The overall cMPR was 0.74 (SD = 0.25); 0.68 (SD = 0.24) for children and 0.81 (SD = 0.24) for adults. Adults presented higher adherence, with overall mean cMPR 0.81 (SD = 0.24) compared to children with mean cMPR 0.68 (SD = 0.24) (p < 0.05, 95% CI = -0.27 to -0.03). Adherence was inversely related to FEV % predicted (β = -0.002, 95% CI = -0.004 to 0, p = 0.023) and FVC% predicted (β = -0.003, 95% CI = -0.005 to -0.001, p = 0.006) in regression analysis. Adherence was not found to be associated with BMI, history of exacerbations and medication complexity. The analysis of each medication showed that adherence to Dornase-alpha, Tobramycin and Colomycin was significantly related to specific disease severity indicators.
CONCLUSION: An overall moderate to high level of adherence was found among our study population. Adults presented higher adherence compared to children. FEV1% and FVC% predicted were related to a significant decrease in adherence. Among our group of CF patients with an overall moderate to high level of adherence, adherence to pulmonary medication was inversely related to disease severity.