Sampling and participants
cardiovascular and cerebrovascular accidents
ACTIVE TUBERCULOSIS
Based on Equations 1, 2, we took deff = 5, α = 95%, During 2018–2019, a multistage stratified cluster sampling procedure was utilized to collect a representative sample from Gansu (Survey points in Gansu Province including Jiuquan, Gannan, Longnan, and Qingyang.All participants were Chinese residents older than 40. Those physically unable to complete the spirometry examination were excluded (active tuberculosis, pregnancy, cardiovascular and cerebrovascular accidents in the past month, heart rate >120 beats/min or blood pressure >180/120 mmHg, related surgeries in the past 3 months, etc.) (Flowchart of screening participants.