Computer rejection rates based on application of original quality control criteria used in the NHANES III study and application of the 2005 ATS/ERS end-of-test (EOT) criteria#

Acceptable blows nOther quality control criteriaRejected n (%)
Age ≥19 years+Age <19 years§
2ƒ  Repeatable FVC  399 (8.7)  171 (5.3)
3  Repeatable FVC  427 (9.3)  183 (5.7)
ATS/ERS EOT criteria [1]
≥2  ≥6 s exhalation##  668 (14.6)  580 (18.1)
2  EOT plateau ≤25 mL over 1 s  655 (13.6)  420 (13.1)
≥2  Plateau ≤25 mL and >6 s exhalation  758 (16.6)  656 (20.4)
≥2  Expiratory time required to achieve a plateau (i.e. ≤25 mL in 1 s) <6 s¶¶  2458 (53.8)  2383 (74.3)
  • Data are presented as n (%). NHANES: National Health and Nutrition Examination Survey; ATS: American Thoracic Society; ERS: European Respiratory Society; FVC: forced vital capacity. #: in addition to the 348 subjects excluded from the original NHANES reference dataset due to <2 acceptable blows, a further 222 had to be excluded on re-analysis, either because the original flow–volume curves could no longer be retrieved or because best FVC varied by >300 mL from the next best. : for the purpose of this analysis, the number of acceptable blows ignores the ATS/ERS statement regarding the need for EOT criteria to be met before blows can be considered “acceptable” unless specified by “other criteria”. For example, of the 4568 subjects aged >19 years who were assessed, 4169 (91.3%) subjects achieved at least two repeatable FVC (irrespective of EOT criteria) whereas only 3411 (85.4%) of these subjects also achieved a plateau and an expiratory time of at least 6 s. +: n=4568. §: n=3209. ƒ: test must have two acceptable blows before any criteria for a repeatable test can be calculated. ##: 6 s exhalation was determined using total expiratory time or the time that the subject continued exhalation regardless of whether a plateau was achieved. ¶¶: time required to reach a plateau with ≤25 mL volume change was ≥6 s, i.e. in 54% and 74% of subjects aged ≥19 years and <19 years, respectively, the actual expiratory time required to reach a plateau (defined as a volume change <25 mL in 1 s) was <6 s.