No Strong Link Between Disease Severity, Therapy Adherence: Study

Patients with good lung function may think they don't need specific pulmonary medicines, researchers posit

Andrea Lobo, PhD avatar

by Andrea Lobo, PhD |

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A poorer adherence to pulmonary therapies does not seem to greatly influence disease severity in patients with cystic fibrosis (CF) who have a nearly normal lung function and good medication adherence rates overall, a study suggests.

For this subgroup of patients, CF severity seems to not be associated with low levels of pulmonary treatment adherence.

The study, Pulmonary medication adherence among children and adults with Cystic Fibrosis: Is there an association with disease severity?, was published in Pediatric Pulmonology.

CF management requires a combination of treatment regimens, usually with long-term use of pulmonary medication, including inhaled antibiotics and mucolytic agents. The adherence to pulmonary medication, meaning the degree to which a patient’s behavior corresponds to the recommendations of the healthcare provider, is pivotal to delay CF disease progression.

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According to the World Health Organization, optimal therapeutic effectiveness requires at least an 80% adherence rate, with a direct impact on disease progression and quality of life. For CF patients, low levels of medication adherence, ranging between 31-79% for pulmonary medications, are a significant problem.

CF severity, treatment adherence

To evaluate the association between medication adherence and disease severity, researchers in Greece performed a retrospective study in 95 CF patients — 52 children (under 18) and 43 adults (above 18), with ages defined at the beginning of the study. Inclusion criteria included a prescription of at least one of the following pulmonary medications: dornase-alpha, inhaled tobramycin, inhaled aztreonam, or inhaled colomycin, for four years.

Researchers analyzed patients’ data from one pediatric and one adult CF unit over four years (2015–2018), using several outcome measures: pulmonary function, body mass index (BMI), history of pulmonary exacerbations, and medication complexity.

This population of CF patients had moderate to high medication adherence, the data showed, with adults having a significantly higher adherence than children. The mean medication possession ratio (MPR) was 0.68 for children and 0.81 for adults, with higher numbers corresponding to higher adherence.

Interestingly, a correlation between a decrease in medication adherence and indicators of lung function was found. Namely, greater percent predicted forced expiratory volume in one second (ppFEV1) and percent predicted forced vital capacity (ppFVC) were associated with a lower medication adherence, indicating that patients with already good lung function tend to be less compliant with pulmonary medications.

The researchers suggested that, given that CF patients with worsening lung function have a higher symptom burden, they probably have a higher adherence to medication in an effort to control their disease. Patients with good lung function may think, on the other hand, they don’t need specific pulmonary medications and have a lower adherence.

The CF group analyzed in the study had “an overall approximately normal lung function, which may explain the absence of association between medication adherence and declined lung function,” the scientists wrote, noting that “research has shown that there is lack of sensitivity in measuring slight changes in healthier populations in lung function measures.”

Regarding other outcomes, no correlation was found between pulmonary medical adherence and BMI, other indicators of lung function, history of pulmonary exacerbations, and the complexity of medication.

Looking into each medication individually, researchers found that adults presented a significantly higher adherence to dornase-alpha and tobramycin compared to children. Both indicators of lung function — ppFEV1 and ppFVC — seemed to be associated with decreased adherence to dornase-alpha, while the number of days of intravenous treatment and hospitalization were related to increased dornase-alpha adherence.

Adhering to tobramycin is related to increased medication complexity (meaning a higher number of medications). Researchers also established an association between colomycin adherence and BMI.

“The analysis of each medication showed that adherence to Dornase-alpha, Tobramycin and Colomycin was significantly related to specific disease severity indicators,” the researchers wrote.

The research team concluded that the “deterioration of the disease is not related to poor adherence in a population of patients with an overall moderate to high levels of adherence. This, in clinical practice, means that achieving an overall high level of adherence probably prevents a decline in health outcomes related to poor adherence and improves the quality of life of patients.”