The saying “rubbish in, rubbish out” emphasizes the importance of accurate measurement in research. Simply put, if our measures aren’t right our results are not valid. Most studies of perinatal PTSD use self-report questionnaires because we need to screen a lot of women in order to identify the small proportion of women who need help. However, if our questionnaires are not accurate it undermines the results of our research.
At the risk of stating the obvious, how we measure PTSD is therefore critical. Clinical interviews are proposed to be the ‘gold standard’ of measurement and some questionnaires have been validated against interviews to determine how sensitivity and specific they are in terms of identifying women with PTSD. However, there are a number of perennial issues we need to consider. These issues include whether to use general PTSD measures or birth-specific measures. Studies suggest that postnatal women might over-report symptoms of hyperarousal and under-report symptoms of avoidance, so birth-specific measures may be more appropriate. Another issue is whether to take a diagnostic approach to PTSD as a ‘disorder’ or a continuum approach focusing on PTSD symptoms. It is clear that some women who do not fulfill diagnostic criteria for PTSD still want and need help. However, there is currently no agreement over what constitutes significant subclinical symptoms. Similarly, different questionnaires focus on a variety of symptoms or diagnostic criteria so we need to be clear about which approach we are taking before we choose our measures. A recent issue is that diagnostic criteria for PTSD changed with the publication of DSM-V but, as yet, questionnaires have not been updated to account for these changes.
The consequence of all of these issues is that it might be difficult at the current time to recommend a measure of PTSD for use with perinatal women and this probably needs to be decided according to the aims of the research. In the meantime, a compromise could be to use multiple measures and, wherever possible, to use clinical interviews. However, it is clear that we desperately need research evaluating different measures and adapting measures to conform to DSM-V diagnostic criteria.