To the Editor:

In response to Dr. Umberger’s comments [1] on the Impact of Event Scale-Revised (IES-R) [2] and the abbreviated 6-item IES (IES-6) [3], we offer guidance about assessing post-traumatic stress disorder (PTSD) symptoms as part of the existing National Institutes of Health-funded core outcome measurement set (COMS) for clinical research in acute respiratory failure (ARF) survivors [4].

An originator of the IES-R is no longer distributing the IES-R because PTSD diagnostic criteria have been revised in the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM–5) [1]. Compared to DSM-IV, the DSM-5 separated the avoidance and numbing criteria and increased the number of associated symptoms from 17 to 20 [5]. However, this revision does not fundamentally change the phenotype of PTSD, and the IES-R/IES-6 continues to have utility in screening for PTSD symptoms [3, 5].

With respect to the above mentioned COMS, existing research has been highly heterogeneous in assessing PTSD, thus limiting advances in the field [4]. A 77-member international modified Delphi expert panel evaluated commonly used PTSD measures based on many criteria, including available psychometric evidence in ARF survivors, with a clear consensus recommendation to use the IES-R [4]. Diagnostic criteria for psychiatric disorders change frequently, without fundamental changes to the phenotype. Hence, without rigorous new research on PTSD screening in ARF survivors and another international consensus process, we do not endorse a unilateral change to the PTSD symptom measure recommended within the existing COMS (more information on the COMS is available at www.improveLTO.com).

In our communication with an originator of the IES-R regarding the above issues, his responses were “I consider it [IES-R] out of copyright …” and “There are enough [IES-R] copies floating around that you can more or less do whatever you want.” (Daniel S. Weiss, September 4, 2019) As evidence supporting the latter comment, we provide exemplar websites and publications that share the IES-R instrument (Table 1).

Table 1 Information on the Impact of Events Scale-Revised (IES-R) and IES-6 items and scoring
Full size table

We hope that this information may provide helpful clarification in screening for PTSD symptoms in ARF survivors, a task that is essential for improving survivorship outcomes.