Reliability of FEV1/FEV6 to diagnose airflow obstruction compared with FEV1/FVC: the PLATINO longitudinal study.
OBJECTIVE
A 6-second spirometry test is easier than full exhalations. We compared the reliability of the ratio of the Forced expiratory volume in 1 second/Forced expiratory volume in 6 seconds (FEV1/FEV6) to the ratio of the FEV1/Forced vital capacity (FEV1/FVC) for the detection of airway obstruction.


METHODS
The PLATINO population-based survey in individuals aged 40 years and over designed to estimate the prevalence of post-Bronchodilator airway obstruction repeated for the same study participants after 5-9 years in three Latin-American cities.


RESULTS
Using the FEV1/FVC<Lower limit of normal (LLN) index, COPD prevalence apparently changed from 9.8 to 13.2% in Montevideo, from 9.7 to 6.0% in São Paulo and from 8.5 to 6.6% in Santiago, despite only slight declines in smoking prevalence (from 30.8% to 24.3%). These changes were associated with differences in Forced expiratory time (FET) between the two surveys. In contrast, by using the FEV1/FEV6 to define airway obstruction, the changes in prevalence were smaller: 9.7 to 10.6% in Montevideo, 8.6 to 9.0% in São Paulo, and 7.5 to 7.9% in Santiago. Changes in the prevalence of COPD with criteria based on FEV1/FVC correlated strongly with changes in the FET of the tests (R(2) 0.92) unlike the prevalence based on a low FEV1/FEV6 (R(2) =0.40).


CONCLUSIONS
The FEV1/FEV6 is a more reliable index than FEV1/FVC because FVC varies with the duration of the forced exhalation. Reporting FET and FEV1/FEV6<LLN helps to understand differences in prevalence of COPD obtained from FEV1/FVC-derived indices.
National Institute of Respiratory Diseases (INER), Mexico City, Mexico. perezpad@gmail.com
Rogelio
R
Perez-Padilla
Fernando C
FC
Wehrmeister
Bartolome R
BR
Celli
Maria Victorina
MV
Lopez-Varela
Maria
M
Montes de Oca
Adriana
A
Muiño
Carlos
C
Talamo
Jose R
JR
Jardim
Gonzalo
G
Valdivia
Carmen
C
Lisboa
Ana Maria B
AM
Menezes
D002947:Cities / Q000706:statistics & numerical data; D005260:Female; D005500:Follow-Up Studies; D005541:Forced Expiratory Volume; D006801:Humans; D007843:Latin America / Q000453:epidemiology; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology*; D015203:Reproducibility of Results; D012129:Respiratory Function Tests / Q000379:methods*; D013147:Spirometry; D014797:Vital Capacity