Serum Prednisolone Levels as a Marker of Oral Corticosteroid Adherence in Severe Asthma

J. Michael Ramsahai; Emily King; Robert Niven; Gael Tavernier; Peter A. B. Wark; Jodie L. Simpson


BMC Pulm Med. 2020;20(228) 

In This Article


Asthma is estimated to affect approximately 300 million people worldwide, with an ever increasing incidence.[1] Within this staggering figure, 5–10% of this population is estimated to have severe asthma, requiring Global Initiative for Asthma (GINA) Step 4 or 5 therapy.[2] A disproportionate amount of the costs due to asthma is accrued by this particular population due to healthcare utilization, medication costs, disability, and lost productivity.[3] In addition, many of the novel biologic agents that are reserved for patients with severe asthma are relatively expensive compared to traditional therapies. As a result, it is important to distinguish truly severe asthma that is refractory to treatment from that which is difficult to control, secondary to poor inhaler technique, inadequate self-management skills, poor adherence, comorbidities, or smoking.[2]

Ensuring adherence to existing therapy is essential to ensure that costly novel therapies are applied to a truly severe asthma population. The GINA guidelines,[4] along with many other international guidelines have established the importance of ensuring adherence to therapy to facilitate this distinction, and ensure that any escalation of therapy is appropriate. Fraction of exhaled nitric oxide (FeNO) suppression testing has been studied to assess adherence to inhaled corticosteroids,[5] however, the assessment of adherence to oral corticosteroid therapy is currently limited to self-reported or indirect outcomes. Commonly used methods include patient interview, medication diaries, pill counts, prescription fill audits, device counters, and electronic device monitors.[6] While useful, many of these options are fraught with potential sources of error. These include them being subjective, open to recall bias, as well as there being an inability to differentiate if medication is taken, absorbed, or administered appropriately. The aim of this study was to examine serum prednisolone levels as a marker of oral corticosteroid adherence in patients with severe asthma and the combination of serum prednisolone levels and sputum eosinophil counts to identify corticosteroid resistant severe asthma.