Serum Inhaled Corticosteroid Detection for Monitoring Adherence in Severe Asthma

BACKGROUND: Daily inhaled corticosteroids (ICSs) are fundamental to asthma management, but adherence is low. OBJECTIVES: To investigate (1) whether LC-MS/MS could be used to detect ICSs in serum and (2) whether serum levels related to markers of disease severity. METHODS: We collected blood samples over an 8-hour period from patients with severe asthma prescribed at least 1000 mu g daily of beclomethasone dipropionate equivalent. Following baseline sampling, patients were observed taking their usual morning dose. Subsequent blood samples were obtained 1, 2, 4, and 8 hours postinhalation and analyzed by LC-MS/MS. Correlations between serum ICS levels and severity markers were investigated. RESULTS: A total of 60 patients were recruited (41 females; 39 prescribed maintenance prednisolone; mean age, 49 +/- 12 years; FENT1, 63 +/- 20 %predicted). Eight hours postinhalation, all patients using budesonide (n = 10) and beclomethasone dipropionate (15), and all but 1 using fluticasone propionate (28), had detectable serum drug levels. Fluticasone furorate was detected in 2 patients (of 4), ciclesonide in none (of 7). Low adherence by repeat prescription records (<80%) was identified in 43%. Blood ICS levels correlated negatively with exacerbation rate, and (for fluticasone propionate only) positively with FEV1 %predicted. CONCLUSIONS: Commonly used ICSs can be reliably detected in the blood at least 8 hours after dosing, and could therefore be used as a measure of adherence in severe asthma. Higher exacerbation rates and poorer lung function (for fluticasone propionate) were associated with lower blood levels. (C) 2021 American Academy of Allergy, Asthma & Immunology