Minimal clinically important difference in idiopathic pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive fibrosing lung disease with an estimated median survival of 2-5 years and a significant impact on quality of life (QoL). Current approved medications, pirfenidone and nintedanib, have shown a reduction in annual decline of forced vital capacity but no impact on QoL. The minimal clinically important difference (MCID) is a threshold value for a change in a parameter that is considered meaningful by the patient rather than solely relying on statistically significant change in the parameter. This review provides a brief overview of the MCID methodology along with detailed discussion of reported MCID values for commonly used physiological measures and patient-reported outcome measures in IPF. While there is no gold standard methodology for determining MCID, there are certain limitations in the MCID literature in IPF, mainly the choice of death, hospitalisation and pulmonary function tests as sole anchors, and pervasive use of distribution-based methods which do not take into account the patient's input. There is a critical need to identify accurate thresholds of outcome measures that reflect patient's QoL over time in order to more precisely design and evaluate future clinical trials and to develop algorithms for patient-oriented management of IPF in outpatient clinics.
Educational Aims: To understand the concept of MCID and the methods used to determine these values.To understand the indications and limitations of MCID values in IPF.
Competing Interests: Conflict of interest: M. Kang reports grants from National Heart, Lung, and Blood Institute (Division T32 grant: 5T32HL116271-07; PI Dr. David Guidot), during the conduct of the study. Conflict of interest: L. Marts reports grants from aTyr Pharma, outside the submitted work. Conflict of interest: J.A. Kempker reports grants from Agency for Healthcare Quality and Research (K08HS025240) and personal fees from Grifols, Inc, outside the submitted work. Conflict of interest: S. Veeraraghavan reports personal fees from Boehringer Ingelheim (Advisory board), and research support grants from Fibrogen, Bellerophon, Biogen, Nitto Denko, Pliant, Galapagos and Galecto, outside the submitted work.
(Copyright ©ERS 2021.)