Background: Associations between healthcare service utilisation (HSU) and airway inflammation in severe asthma or COPD patients remain unclear.

Aim: To relate quantitative cell counts in sputum to HSU (hospitalizations, physician visits, emergency department visits) patterns in asthma or COPD patients.

Methods: Clinical data, spirometry, and sputum cell counts (% of eosinophil, neutrophils) were collected between 2006-2022 and linked to health administrative databases. Negative binomial regression analyses estimated rate ratios (RR) and 95% confidence intervals (CI) of HSU while adjusting for other covariates.

Results: Of the 4821 patients included, 3714 (77%) had asthma only and 1107 (23%) had COPD only. Overall, those with higher eosinophil (>15%) and lower neutrophil counts (<65%) had significantly higher rates of asthma-specific and asthma-related HSU. In asthma patients, higher eosinophil cell counts were associated with higher asthma-specific ED visit rates (RR=1.84, 95%CI: 1.14-2.95). Compared to patients with both lower eosinophil and neutrophil counts, higher eosinophil and neutrophil cell counts had a 73% higher rate for asthma-specific physician visits (95%CI: 1.18-2.52). Eosinophil counts were not significantly associated with HSU in COPD patients. High neutrophil counts in COPD patients were significantly associated with all-cause hospitalizations (RR=1.57, 95%CI: 1.02-2.42).

Conclusions: This is the first demonstration of the association between objective cellular evidence of airway inflammation and HSU in patients with asthma. Eosinophils in the airway may not directly contribute to disease pathobiology in COPD. This requires further investigation.