LAUSR

(progression over 6 mo to 2 y) (2) have occasionally been misunderstood to require. However, it may be challenging to ascertain progression over 12 months. Travel distance, logistics, or even a pandemic may conspire to delay and/or prevent routine measures of disease activity. Conversely, there is often no reason to wait, with disease progression clearly occurring over a shorter period of time (e.g., 3–9 mo). In this situation, clinically relevant changes should be identified as early as possible. We propose that criteria for progression should be dissociated from the timelines during which they occur. In essence, in the absence of another explanation for the measured changes, progression is progression, whether it occurs at 3 months or 3 years. For example, an absolute decline in FVC of more than 5% predicted (a threshold chosen to exceed measurement variability) indicates disease progression, whatever the timelines. Although strict criteria are required to define eligibility criteria in clinical trials, in an individual patient, it is the responsibility of the bedside clinician to make the best management decision. This decision may differ if disease progression is recognized to have occurred over 3, 6, 9, 12, 24, or 36 months. Disease progression, at whatever rate, should lead to a reevaluation of current management, often including the institution of antifibrotic therapy. Rapid progression, as opposed to insidious progression, may reduce the threshold for management change. So that the criteria may not be inadvertently misinterpreted by clinicians and regulatory bodies, we wish to stress that it is not required that progression occurs over a full 1-year period. We further suggest that, whereas thresholds of physiologic and radiologic disease progression are well-defined by guidelines, the timelines over which progression takes place and their implications should be left to the discretion of the clinicians, taking into account patient preferences and benefit:risk ratio of the management strategy, and to those who design the clinical studies.