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Abstract
Background
Posttraumatic stress disorder (PTSD) symptoms are common in acute respiratory distress
syndrome (ARDS) survivors. Brief screening instruments are needed for clinical and
research purposes. We evaluated internal consistency, external construct, and criterion
validity of the Impact of Event Scale-6 (IES-6; 6 items) compared to the original
Impact of Event Scale—Revised (IES-R; 22 items) and to the Clinician Administered
PTSD Scale (CAPS) reference standard evaluation in ARDS survivors.
Methods
This study is a secondary analysis from two independent multi-site, prospective studies
of ARDS survivors. Measures of internal consistency, and external construct and criterion
validity were evaluated.
Results
A total of 1001 ARDS survivors (51% female, 76% white, mean (SD) age 49 (14) years)
were evaluated. The IES-6 demonstrated internal consistency over multiple time points
up to 5 years after ARDS (Cronbach’s alpha = 0.96; 95% confidence interval (CI) 0.94
to 0.97). The IES-6 demonstrated stronger correlations with related constructs (e.g.,
anxiety and depression; |r| = 0.32 to 0.52) and weaker correlations with unrelated
constructs (e.g., physical function and healthcare utilization measures (|r| = 0.02
to 0.27). Criterion validity evaluation with the CAPS diagnosis of PTSD in a subsample
of 60 participants yielded an area under receiver operating characteristic curve (95%
CI) of 0.93 (0.86, 1.00), with an IES-6 cutoff score of 1.75 yielding 0.88 sensitivity
and 0.85 specificity.
Conclusions
The IES-6 is reliable and valid for screening for PTSD in ARDS survivors and may be
useful in clinical and research settings.