Idiopathic pulmonary fibrosis (IPF) is a relentlessly progressive disease that usually leads to death within 5 yr of diagnosis (1-4). Because a response to current therapeutic agents is unusual, treatment is unlikely to alter outcome in most patients (5). Nonetheless, prognosis will have an effect on the decision of whether or not to treat. Some individuals with this disease will survive for many years, a fact that highlights the variability of the natural history of this disease (4, 6). Determining factors that predict the outcome has become increasingly important because lung transplantation is now an accepted therapy for selected candidates (7). In addition, patients typically seek advice about how long they might live so that they and their families may plan for the future and establish appropriate supportive care for advanced disease (8). For these reasons, clinicians have attempted to develop indicators that will reliably predict longevity in patients with IPF.

Early studies (1, 9-12) identified a number of factors (Table 1) that seem to affect survival, but these studies must be interpreted in light of their limitations. These include: retrospective design, lack of histologic confirmation of usual interstitial pneumonia (UIP), lack of high-resolution computed tomography (HRCT) scans to assess inflammation and fibrosis in a semiquantitative manner, relatively small numbers of subjects, and inadequate duration of follow-up. Recent efforts to clarify the histopathology of idiopathic interstitial pneumonias (13) and the advent of more advanced imaging and lung biopsy techniques allows for a more rigorous approach to the diagnosis of IPF. A consensus statement recently released by the American Thoracic Society and European Respiratory Society details the present understanding of the pathogenesis of IPF and offers rational recommendations for confirming the diagnosis and for therapy (7). This report highlights the challenges in making a confident diagnosis of IPF. Contemporaneous reports emphasize the differences in survival between IPF and the other idiopathic interstitial pneumonias such as nonspecific interstitial pneumonia (NSIP)(3, 13-15). Incorrect inclusion of patients with the latter disease into outcome studies for the former disease will certainly confound the results by overestimating the survival in IPF. With the emergence of the new classification for idiopathic interstitial pneumonias, it is necessary to consider only studies that use the currently accepted diagnostic criteria in determining the factors affecting survival for patients with IPF. The purpose of this short review is to summarize the results of such studies and to suggest additional quantitative methods for determining extent of disease and its impact on outcome.