Table 6.

Summary of characteristics of various reference standards

Reference equation and date of publication	Type of Instrument and ability to meet ATS specifications	Time zero technique	Population characteristic	Method of screening
NHANES III-1999 Hankinson et al 1999	Dry rolling-seal spirometer with a digital shaft encoder, met ATS specifications	Back extrapolation	Nonsmoker Caucasians, African Americans, and Mexican Americans	History
Morris et al 1971	Stead-Wells, met ATS specifications	Kory technique	988 rural non-Hispanic white nonsmokers, largely of Mormon sect, in an area <150 ms. altitude, free of air pollution	History
Kory et al 1961	Collins 13.5 L metal bell, met ATS specifications	Kory technique	Hospital employees, patients, medical students, doctors in urban locale	History, physical examination, chest radiographs, and electrocardiogram
Crapo et al 1981	Collins 13.5 L metal bell, met ATS specifications	Back extrapolation	Urban, non-Hispanic white nonsmokers, largely of Mormon sect, at an altitude of 1,400 ms.	History, physicalexamination, andchest radiographs
Knudson et al 1976	Pneumotachygraph, met ATS specifications	Back extrapolation	746 nonsmoker, non-Mexican white population, without pregnant women, at 730 ms. altitude	History
Knudson et al 1983	Pneumotachygraph, met ATS specifications	Back extrapolation	697 nonsmoking non-Mexican white population	History