Study subjects
For GWAS, the subjects were obtained from three hospitals; Asan Medical
center (AMC), Seoul National University Gangnam Center of Seoul National
University Hospital (SNUH) and Kang-Won National University Hospital
(KNUH). Of 1,386 asthma patients, 1,293 patients were from AMC between
January 2005 and December 2018. The inclusion criteria were (1) aged
>18 years, (2) symptoms such as dyspnea, wheezing, or cough
for more than 3 months, and (3) airway hyperresponsiveness as indicated
by a 20% reduction in forced expiratory volume in 1 second (FEV1) with
a methacholine dose of 16 mg/mL (PC 20) through a provocation test or
airway reversibility as indicated by an increase in FEV1 of
> 12% (and at least 200 mL) following the inhalation of a
short- acting β-agonist. Patients with severe lung damage,
bronchiectasis, or a history of lung resection were excluded. From the
SNUH, 93 asthmatic patients were included, who provided a “yes”
response to any of the following questions: “Have you ever been
diagnosed with asthma?” or “Have you ever taken asthma medication at
least once?”. Of 5,205 controls, 5,161 and 44 controls were from SNUH
and KNUH, respectively, and they were not diagnosed with asthma and
chronic obstructive pulmonary disease (COPD). The study was approved by
the Institutional Review Board (2019-1676) of all participating
institutions.