Figure 1.

Schematic representation of the potential clinical courses of idiopathic pulmonary fibrosis. As disease progresses there is a subclinical period in which only radiographic findings of disease may be present, followed by a symptomatic period consisting of both pre- and post-diagnosis clinical phases. The rate of decline and progression to death may be rapid (A), slow (C and D) or mixed (B), with periods of relative stability interposed with periods of acute decline (#). Reproduced from [11] with permission.