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The clinical evaluation for diagnosing obstructive airways disease in high-risk patients
R G Badgett1, D J Tanaka, D K Hunt
1Department of Internal Medicine, University of Texas Health Science Center at San Antonio 78284-7879.
Objective:
We measured the ability of the medical history, physical examination, and peak flowmeter in diagnosing any degree of obstructive airways disease (OAD).
Design:
Prospective comparison of historical and physical findings with independently measured spirometry.
Setting:
University outpatient clinic.
Patients:
Ninety-two adult consecutive outpatient volunteers with a self-reported history of smoking, asthma, chronic bronchitis, or emphysema.
Measurements:
All subjects completed a pulmonary history questionnaire and received peak flow (PF) and spirometric testing. The subjects were independently examined for 12 pulmonary physical signs by four internists blinded to all other results. Multivariable analysis was used to create a diagnostic model to predict OAD as diagnosed by spirometry (FEV1 < 80 percent of predicted not secondary to restrictive disease, or FEV1/FVC less than 0.7).
Results:
The best model diagnosed OAD when any of three variables were present--a history of smoking more than 30 pack-years, diminished breath sounds, or peak flow less than 350 L/min. This model had a sensitivity of 98 percent and specificity of 46 percent. In addition, the model detected all subjects with probable restrictive lung disease. Thirty-one percent of subjects had none of these variables and were at very low (3 percent) risk of OAD. Fifty percent of subjects with one or more abnormal variables had OAD.
Conclusions:
The history, physical examination, and peak flowmeter can be used to screen high-risk patients for OAD. Using this diagnostic model, 31 percent of subjects could be classified at very low risk of OAD while half of those referred for spirometry would have abnormal results.