Re-examining baseline lung function recovery following IV-treated pulmonary exacerbations.

CF registry pulmonary exacerbation (PEx) analyses have employed "before and after" spirometry recovery, where the best percent predicted forced expiratory volume in 1 s (ppFEV) prior to PEx ("baseline") is compared to the best ppFEV <3 months post-PEx. This methodology lacks comparators and ascribes recovery failure to PEx. Herein, we describe 2014 CF Foundation Patient Registry PEx analyses including a comparator: recovery around nonPEx events, birthdays. 49.6% of 7357 individuals with PEx achieved baseline ppFEV recovery while 36.6% of 14,141 achieved baseline recovery after birthdays; individuals with both PEx and birthdays were more likely to recover baseline after PEx than after birthdays (47% versus 34%); mean ppFEV declines were 0.3 (SD=9.3) and 3.1 (9.3), respectively. Post-event measure number had more effect on baseline recovery than did real ppFEV loss in simulations, suggesting that PEx recovery analyses lacking comparators are prone to artifact and poorly describe PEx contributions to disease progression.