					Reproducibility (% adequate)

Author, publication year	Country	Setting	Study population	Number of patients	FEV₁, %	FVC, %
Primary care practice
Schermer et al,^I 2009 (current paper)	The Netherlands	Routine care	Adults and children ≥12 years from 15 primary care practices	1091	43	40
Tuomisto et al, 200827	Finland	Routine care	Patients from primary care health centres	489	78 to 80^a^,^b
Walters et al, 200828	Australia	Research	Adults from eight primary care practices	618	44 to 76^a^,^c
Eaton et al,^II 19999	New-Zealand	Research	Adults and children from 30 primary care practices	1012	3 to 14^a^,^c
Schermer et al,^I 200322	The Netherlands	Research	Patients with COPD recruited from 61 primary care practices	399	82^d	–
Zanconato et al,^III 200529	Italy	Research	Children from 10 primary care paediatric practices	109	94^a

Pulmonary function laboratory
Enright et al,^IV 200430	US	Routine care	Adult patients from one outpatient pulmonary function laboratory	18 000	>95	>90
Enright et al,^V 200015	US	Routine care	Public schools students aged 9–18 years from middle-income communities	4000	93	97
Bellia et al,^VI 200019	Italy	Research	Patients ≥65 years attending one of the 24 involved pulmonary or geriatric institutions	1622	>94	>87
Stoller et al,^II 199731	US	Research	Patients with severe α1 antitrypsin deficiency, from 37 hospitals	1090	>95	>91
Enright et al,^VII 199116	US	Research	Cigarette smokers 35 to 60 years of age included in a clinical trial	5887	>99	–

Studies conducted in pulmonary function laboratories are included as points of reference. Studies have used different definitions for reproducibility, which limits direct comparison of results.32
Definitions used in the respective studies are:
↵I Two highest FEV₁ values <5% and <200 ml;
↵II Largest FEV₁ values and largest FVC values ≤200 ml;
↵III Two highest FEV₁ values and FVC values ≤5%;
↵IV Difference between highest and second-highest FEV₁ <150 mL;
↵V FVC and FEV₁ values at least 95% of the largest values;
↵VI Difference between highest and second-highest value <200ml for FEV₁ and FVC;
↵VII Difference between highest and second-highest FVC <200ml.
↵a Reproducibility results not reported for FEV₁ and FVC separately.
↵b For pre- and postbronchodilator tests respectively.
↵c For usual and trained practices respectively.
↵d Reproducibility calculated without prior selection of acceptable blows according to 1994 American Thoracic Society spirometry guidelines.6
COPD = chronic obstructive pulmonary disease.