Does A Normal FEV1/FVC Ratio In Patients With Normal FEV1 And FVC Rule Out Obstructive Lung Disease?

In individuals with both normal FEV1 and FVC, a normal ratio can discourage a health care provider from pursuing further diagnostic work up and therefore they are at risk for misdiagnosis. Our objective was to examine whether a normal FEV1/FVC in individuals with both normal FEV1 and FVC is sufficient to rule out obstructive lung disease. We compared retrospectively the sensitivity and specificity of FEV1/FVC below the lower limit of normal, FEV1/FVC below 0.7, and air trapping and/or hyperinflation by plethysmography to diagnose radiographic obstructive lung disease. We included 455 patients, 80 (17.6%) of whom had radiographic findings of obstructive lung disease. The sensitivities of all 3 diagnostic criteria to diagnose radiographic obstructive lung disease were below 19%. Positive (PPVs) were 12.1-16.3% for each criterion, while negative predictive values (NPVs) were 80.4-82.3%.In patients with both normal FEV1 and FVC, a normal FEV1/FVC is associated with approximately 20% probability of radiographic findings of obstructive lung disease.