Which prognostic indicator should we use for clinical practice in the initial evaluation and follow-up of IIP: Should we depend on PFT, HRCT or ... what?

Idiopathic interstitial pneumonias are a group of diffuse, inflammatory and fibrotic disorders of the lung parenchyma that cause restrictive physiology and impair gas exchange. Usual interstitial pneumonia and non-specific interstitial pneumonia comprise the majority of idiopathic interstitial pneumonia cases. Previous studies have identified the histopathologic pattern as the most important baseline factor in determining prognosis. The non-invasive diagnosis of these diseases is sometimes uncertain but histological evaluation is an imperfect gold-standard. In some cases, the biopsy specimen may not be representative of the entire lung. In other cases, there may be differences in interpretation of the histological findings. HRCT has also assumed a greater role in the diagnosis and management of patients with idiopathic interstitial pneumonia. Factors affecting prognosis are discussed controversially. Histological criteria, clinical features, or lung function parameters are not clear prognostic indicators. Increased interstitial abnormalities in the HRCT, parameters indicating restrictive lung function, desaturation at 6MWT and abnormal gas exchange are possible determinants of survival. The prognostic value of pulmonary function trends over time may prove more useful. Longitudinal behavior is a more accurate determinant of outcome than evaluation at a single point in time. It is important to remember that no predictor of survival can ever reliably predict an individual patient's prognosis. Physicians should realize this limitation, and use predictor tools as general prognostic guides, not crystal balls. However, due to the great variability in the natural history of the disease, close monitoring of the patients may be necessary to evaluate the individual course of each patient.