Blood Eosinophil Count and Outcomes in Severe Uncontrolled Asthma: A Prospective Study.
Severe uncontrolled asthma (SUA) is associated with increased asthma exacerbations. Whether high blood eosinophil counts are related to this burden is uncertain.



To determine the relationship of blood eosinophil counts to asthma exacerbations, utilization, and cost in patients with SUA.



Patients with persistent asthma (age ≥ 12 years) were identified administratively with SUA in phase I by evidencing (1) 2 or more asthma exacerbations; (2) 6 or more medium- or high-dose dispensed canisters of inhaled corticosteroid (ICS) as monotherapy or with long-acting β2-agonist; and (3) 3 or more dispensed non-ICS controllers. Of the 541 patients with SUA invited to participate in the prospective phase II follow-up study, 261 (48.2%) had blood tests (index date) to determine eosinophil count and other atopic biomarkers. The relationship of blood eosinophil cutoff points to asthma exacerbations and direct costs 1 year after the index date were determined by multivariable regression.



A blood eosinophil cutoff point of greater than or equal to 400 cells/mm3compared with less than 400 cells/mm3, but not 150 cells/mm3or 300 cells/mm3, was a risk factor in the outcome year in adjusted analyses for 2 or more asthma exacerbations (risk ratio, 1.55; 95% CI, 1.02-2.35; P =.04) and any asthma emergency department visit or hospitalization (risk ratio, 2.29; 95% CI, 1.16-4.55; P =.02), but not for rate of asthma exacerbations or incremental total direct asthma costs per patient ($202; 95% CI, -286 to 691).



A high blood eosinophil count was an independent risk factor for 2 or more asthma exacerbations or any asthma emergency department visit or hospitalization, but not direct costs in patients with SUA, possibly constrained by limited power.
Kaiser Permanente Southern California Region, San Diego and Pasadena, Calif. Electronic address: robert.s.zeiger@kp.org.
Robert S
RS
Zeiger
Kaiser Permanente Southern California Region, San Diego and Pasadena, Calif.
Michael
M
Schatz
GlaxoSmithKline, Research Triangle Park, NC.
Anand A
AA
Dalal
Kaiser Permanente Southern California Region, San Diego and Pasadena, Calif.
Wansu
W
Chen
Kaiser Permanente Southern California Region, San Diego and Pasadena, Calif.
Ekaterina
E
Sadikova
GlaxoSmithKline, Research Triangle Park, NC.
Robert Y
RY
Suruki
Kaiser Permanente Southern California Region, San Diego and Pasadena, Calif.
Aniket A
AA
Kawatkar
Kaiser Permanente Southern California Region, San Diego and Pasadena, Calif.
Lei
L
Qian
D000328:Adult; D000368:Aged; D018927:Anti-Asthmatic Agents / Q000627:therapeutic use; D001249:Asthma / Q000175:diagnosis* / Q000188:drug therapy; D015415:Biomarkers; D001773:Blood Cells / Q000473:pathology*; D002452:Cell Count; D018450:Disease Progression; D004804:Eosinophils / Q000473:pathology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012008:Recurrence; D016896:Treatment Outcome
D018927:Anti-Asthmatic Agents; D015415:Biomarkers
Asthma control; Blood eosinophil count; Controller medication; Cost; Persistent asthma; Severe uncontrolled asthma; Utilization