A significant proportion of patients with difficult-to-control asthma are nonadherent to inhaled and oral corticosteroid therapy, research published in the American Journal of Respiratory and Critical Care Medicine has found.
Investigators from the Queen’s University of Belfast and Belfast City Hospital assessed 182 patients who had been referred to the difficult asthma clinic in the city because of persistent symptoms despite treatment at GINA step 4/5.
The researchers compared GP refill records for the previous 6 months for inhaled combination therapy and short-acting beta-agonists, with the initial prescriptions, and calculated this as a percentage. Blood plasma prednisolone and cortisol assay levels were used to see if they had potential in identifying nonadherence to oral prednisolone.
None of the patients in the study had nonadherence initially suspected as a major clinical cause of poor control of their asthma. All of them denied nonadherence when they were interviewed at the first clinical assessment at the difficult asthma clinic.
The authors found that 63 patients (35%) filled fewer than half of their prescriptions for inhaled combination therapy (ICT) – but 21% filled more than 100% of them; 45% of subjects filled between 51% and 100% of prescribed medication. Women were significantly more likely than men to be nonadherent with ICT but there were no age differences between the groups.
Patients who had filled fewer than half of their ICT prescriptions were more likely than others to have had three or more hospital admissions in the previous 12 months.
Researchers were able to follow up 51 of the 63 patients who had filled fewer than half of their prescriptions. When they discussed nonadherence with these people, 45 (88%) admitted variability in taking ICT at a level that is consistent with the level of nonadherence shown by their prescription records. The remaining six patients denied nonadherence with ICT even though they had a low rate of prescription filling, and three had undetectable levels of cortisol or theophylline even though they said they were taking those therapies.
The authors recognise that patients may be reluctant to take steroid therapy, especially systemic steroids “with their greater and more readily attributable side-effects”. They speculate that if their patients at the difficult asthma clinic took regular preventative therapy as prescribed, their asthma would probably improve substantially.
Am J Respir Crit Care Med Vol 180. pp817-822, 2009
