The following is a summary of “An observational study to determine the relationship between cough frequency and markers of inflammation in severe asthma” published in the December 2022 issue of Respiratory by Holmes et al.
The link between an objectively determined cough and type 2 (T2) biomarkers and other indices of asthma control and severity indices is poorly known. The purpose of this investigation was to compare and contrast different methods of measuring cough with clinical indicators of asthma. Methods Patients with severe asthma and mild-to-moderate asthma performed spirometry, T2 biomarkers (exhaled nitric oxide fraction (FENO) and peripheral blood eosinophil count), and cough-related measuring techniques (including ambulatory cough monitoring).
Patients were classified according to T2 status based on T2-low (FENO <20 ppb and peripheral blood eosinophils <150 cells·µL-1), T2-intermediate (FENO ≥20 ppb or peripheral blood eosinophils ≥150 cells·µL−1) or T2-high (FENO ≥20 ppb and peripheral blood eosinophils ≥150 cells·µL-1). Outcomes A total of 61 participants were measured for the study severe asthma and 19 for mild-to-moderate asthma). Both the total number of coughs in 24 hours (geometric means 170.3±2.7 versus 60.8±4.1; P=0.002) and the number of coughs per hour (geometric means±SD 7.1±2.7 versus 2.5±4.1 coughs -1; P=0.002) were greater in patients with severe asthma compared to those with mild-to-moderate asthma.
Total 24- hour cough frequency was considerably reduced in T2-low individuals with severe asthma compared to T2-intermediate and T2-high patients. Cough frequency measurements were not elevated in patients with low T2 biomarkers, suggesting that underlying T2 eosinophilic inflammation is the mechanism for cough in asthma. Therefore, achieving adequate suppression of T2 inflammation with current therapies may be the logical first step in treating cough in asthma.