Presence of the high-resolution computed tomography (HRCT) pattern of UIP
Pulmonary hypertension at rest (20-40%) : Loud P2 component of the second heart sound, a fixed split S2, a holosystolic tricuspid regurgitation murmur, pedal edema
Specific combinations of HRCT patterns and histopathology patterns in patients subjected to lung tissue sampling
Surgical lung biopsy (via open lung biopsy or video-assisted thoracoscopic surgery [VATS] [preferred]): Best sample for distinguishing usual interstitial pneumonia from other idiopathic interstitial pneumonias.
Fine bibasilar inspiratory crackles (Velcro crackles): Noted in most patients
C-reactive protein level and erythrocyte sedimentation rate: Elevated but nondiagnostic in idiopathic pulmonary fibrosis
Antinuclear antibodies or rheumatoid factor titers: Positive results in about 30% of patients with IPF, but the titers are generally not high. The presence of high titers may suggest a connective tissue disease
Exclusion of known causes of interstitial lung disease
Bronchoscopy: Absence of lymphocytosis in bronchoalveolar lavage fluid may be important for the diagnosis (increased neutrophils [70-90% of patients] and eosinophils [40-60% of all patients]). This procedure may be used to exclude alternative diagnoses.
Pulmonary function studies: Nonspecific findings of a restrictive ventilatory defect and reduced diffusion capacity for carbon monoxide (DLCO)
Complete blood cell count: polycythemia (rare)
Digital clubbing (25-50%) Pulmonary hypertension at rest (20-40%)
Transthoracic echocardiography: Detects pulmonary hypertension well but has variable performance in patients with idiopathic pulmonary hypertension and other chronic lung disease
High-resolution computed tomography (HRCT) scanning: Sensitive, specific, and essential for the diagnosis of idiopathic pulmonary fibrosis. Demonstrates patchy, peripheral, subpleural, and bibasilar reticular opacities.
Chest radiography: Abnormal findings but lacks diagnostic specificity. Demonstrate peripheral reticular opacities (netlike linear and curvilinear densities) predominantly at the lung bases, honeycombing (coarse reticular pattern), and lower lobe volume loss
Arterial blood gas analysis: chronic hypoxemia (common)
