Efficient screening for COPD using three steps: a cross-sectional study in Mexico City.
BACKGROUND
Underdiagnosis of chronic obstructive pulmonary disease (COPD) in primary care can be improved by a more efficient screening strategy.


OBJECTIVE
To evaluate a three-step method of screening for COPD consisting of an initial short questionnaire followed by measurement of forced expiratory volume in 1s/forced expiratory volume in 6s (FEV1/FEV6) using an inexpensive pocket spirometer in those with high risk, and diagnostic quality spirometry in those with a low FEV1/FEV6.


METHODS
We analysed two related Mexico City cross-sectional samples. The 2003 Mexico City PLATINO survey (n=542) was used to develop a short questionnaire to determine the risk of COPD and a 2010 survey (n=737) additionally used a pocket spirometer. The discriminatory power of the two instruments was assessed with receiver operator characteristic (ROC) curves using three COPD definitions.


RESULTS
The developed COPD scale included two variables from a simple questionnaire and, in ROC analysis, an area under the curve (AUC) between 0.64 and 0.77 was found to detect COPD. The pocket spirometer had an AUC between 0.85 and 0.88 to detect COPD. Using the COPD scale as a first screening step excluded 35-48% of the total population from further testing at the cost of not detecting 8-18% of those with COPD. Using the pocket spirometer and sending those with a FEV1/FEV6<0.80 for diagnostic quality spirometry is very efficient, and substantially improved the positive predictive value at the cost of not detecting one-third of COPD cases.


CONCLUSIONS
A three-step screening strategy for COPD substantially reduces the need for spirometry testing when only a COPD scale is used for screening.
Department of Epidemiology, National Institute of Respiratory Diseases, Mexico City, Mexico.
Francisco
F
Franco-Marina
Department of Epidemiology, National Institute of Respiratory Diseases, Mexico City, Mexico.
Rosario
R
Fernandez-Plata
Department of Epidemiology, National Institute of Respiratory Diseases, Mexico City, Mexico.
Luis
L
Torre-Bouscoulet
Department of Epidemiology, National Institute of Respiratory Diseases, Mexico City, Mexico.
Cecilia
C
García-Sancho
Department of Epidemiology, National Institute of Respiratory Diseases, Mexico City, Mexico.
Elisa
E
Sanchez-Gallen
Department of Epidemiology, National Institute of Respiratory Diseases, Mexico City, Mexico.
David
D
Martinez
Department of Epidemiology, National Institute of Respiratory Diseases, Mexico City, Mexico.
Rogelio
R
Perez-Padilla
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D008800:Mexico / Q000453:epidemiology; D008875:Middle Aged; D011320:Primary Health Care / Q000379:methods; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013147:Spirometry / Q000295:instrumentation / Q000379:methods; D011795:Surveys and Questionnaires