Reply to Do 1 in 5 cancer patients develop post-traumatic stress disorder?

Abstract

We sincerely appreciate the effort that Turner and Hancock have made to point out that the incidence of post-traumatic stress disorder (PTSD) would have been lower if the total study sample, rather than just those who had undergone the Structured Clinical Interview for DSM-IV Axis I Disorders (SCID), had been used as a denominator.1 Because the percentage depends on the denominator, we sought to make it as clear as possible that the rate of PTSD at the 6-month follow-up was condition-specific by outlining from the start that this percentage was based on patients with elevated psychological distress who had completed the SCID. We used the basis of undergoing the SCID at both the 6-month follow-up and the 4-year follow-up to standardize the calculation of the percentages. All patients underwent the SCID for PTSD at the 4-year follow-up; however, at the 6-month follow-up, only those with elevated distress did. It would not be accurate to base the incidence of PTSD on a denominator including participants who had not undergone the SCID. First, this would be misleading in that it would inflate the number of patients who seemingly had undergone the SCID. Second, we could not reasonably aggregate patients who had undergone the SCID with those who had not done so into a single group for the following reason: we explicitly stated as a limitation of the study that we did not conduct the SCID for all patients at the 6-month follow-up, so we could not determine whether nonprobable cases had PTSD in the short term. This also means that we certainly could not assume that patients in the nonprobable PTSD group did not have PTSD; therefore, we could not reasonably group these patients together with those who had undergone the SCID. This was why we chose to separate and differentiate patients with nonprobable PTSD into a group of their own. We made every effort to separate this out in the Methods, Results, and Discussion sections to facilitate a fairer comparison across the 2 different groups and time periods. This was decided because it best reflects routine clinic practice, where it would be unusual to perform the SCID for every single patient with cancer; therefore, we made the decision to conduct the SCID only for patients with elevated distress. This consideration led us to state the percentages as is (a condition-specific percentage). In the interests of transparency, we also took every care to ensure throughout the Results and Discussion sections that that the denominator for the percentage listed was clearly stated to be based on the number of patients who had elevated distress and had completed the SCID. Unfortunately, it is true that in the media, this has been widely abbreviated to “1 in 5 patients with cancer have PTSD”: it is not always clear that this percentage is for the 6-month follow-up and that it includes subsyndromal PTSD cases. In summary, we believe that the published percentage is supported by our data, although it is subject to interpretation. We also urge future researchers to consider this other interpretation when they are examining this study. Funding was provided by a Young Investigator's Grant (GGPM-2017-131) from the National University of Malaysia. The authors made no disclosures. Caryn Mei Hsien Chan, PhD National University of Malaysia Kuala Lumpur, Malaysia Chong Guan Ng, PhD University Malaya Medical Centre Kuala Lumpur, Malaysia Aishah Taib, MD University Malaya Medical Centre Kuala Lumpur, Malaysia Lei Hum Wee, PhD Faculty of Health Sciences National University of Malaysia Kuala Lumpur, Malaysia Edward Krupat, PhD Center for Evaluation Harvard Medical School Boston, Massachusetts Fremonta Meyer, MD Dana-Farber Cancer Institute Boston, Massachusetts