Appropriate identification of subjects who are candidates for spirometry through case-finding questionnaires may help solve the problem of chronic obstructive pulmonary disease misdiagnosis. The performance of case-finding questionnaires depends at least partially on the characteristics of the population used for their development. The use of an accurate threshold for the forced expiratory volume in 1 second / forced vital capacity ratio to define persistent airway obstruction is also vital in ascertaining chronic obstructive pulmonary disease.
