Development of the Lung Function Questionnaire (LFQ) to identify airflow obstruction.
OBJECTIVE
To describe the item-selection and item-reduction for the Lung Function Questionnaire (LFQ), being developed to help clinicians identify patients appropriate for diagnostic evaluation for chronic obstructive pulmonary disease (COPD) using spirometry.


METHODS
Item selection and reduction were based on information from 387 > or =40-year-old respondents to the third National Health and Nutrition Examination Survey who had self-reported chronic bronchitis. Item reduction involved stepwise logistic regression. The accuracy of the final subset of items for identifying individuals with airflow obstruction (forced expiratory volume in one second/forced vital capacity <0.70) versus those without it was assessed with receiver operating characteristic analysis. Content and face validity were assessed using focus groups of primary care physicians (n = 16) and interviews with COPD patients (n = 16).


RESULTS
The model with all five items (age; smoking history; the presence of wheeze, dyspnea, and phlegm) compared with models with combinations of fewer items had the highest classification accuracy (area under the curve [AUC] = 0.720) with sensitivity and specificity of 73.2% and 58.2%, respectively. The presence of three or more factors yielded the highest AUC, a result suggesting that three or more affirmative answers is the most appropriate criterion indicating presence of airflow obstruction.


CONCLUSIONS
The five-item LFQ retained sufficient accuracy, sensitivity, and specificity in identifying individuals with COPD for further validation testing.
Yawn
Barbara P
BP
Olmsted Medical Center, Department of Research, Rochester, MN, USA. yawnx002@umn.edu
Mapel
Douglas W
DW
Mannino
David M
DM
Martinez
Fernando J
FJ
Donohue
James F
JF
Hanania
Nicola A
NA
Kosinski
Mark
M
Rendas-Baum
Regina
R
Mintz
Matthew
M
Samuels
Steven
S
Dalal
Anand A
AA
D000328:Adult; D003937:Diagnosis, Differential; D005260:Female; D017144:Focus Groups; D006801:Humans; D007407:Interviews as Topic; D008168:Lung / Q000503:physiopathology; D008297:Male; D008403:Mass Screening / Q000295:instrumentation*; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis* / Q000503:physiopathology; D013147:Spirometry; D011795:Surveys and Questionnaires / Q000592:standards*