Immunological phenotype in asthma and its impact on long-term renal outcomes

Asthma is associated with both airway and systemic inflammation as well as non-respiratory adverse outcomes. However, data regarding its impact on long-term renal outcomes is lacking. We classified all asthma patients who were followed at Queen Mary Hospital in 2017 into eosinophilic or non-eosinophilic phenotypes based on their highest blood eosinophil counts (BEC) during stable state in the year (≥ 300 or < 300 cells/mm³ respectively) and prospectively evaluated their clinical outcomes in the subsequent 5 years. The relationship between patient phenotypes and the long-term renal outcomes were assessed. Five hundred and four asthma patients with baseline Stage 1 to 3 chronic kidney disease were included [296 (58.7%) and 208 (41.3%) in eosinophilic and non-eosinophilic groups respectively]. Among patients with baseline renal function at CKD stage 1 to 3, one hundred and four patients (20.6%) had renal progression in this cohort (56 patients (26.9%) vs. 48 patients (16.2%) in the non-eosinophilic and eosinophilic groups respectively). Patients with non-eosinophilic asthma showed increased risks of renal progression over 5 years of follow-up [adjusted odds ratio (aOR) 2.615, 95% CI 1.151-5.942 p = 0.022] and more rapid eGFR decline (-4.29 ± 3.48 mL/min/1.73m²/year vs. -3.48 ± 3.07 mL/min/1.73m²/year, p = 0.007) than those with eosinophilic phenotype. Patients who developed renal progression had higher risk of death [adjusted hazard ratio (aHR) 1.614 (95% CI 1.041-2.502); p = 0.032]. Progressive renal function deterioration is prevalent amongst asthma patients, and those with non-eosinophilic phenotype are at risk of renal progression.