INTERVIEWER EFFECTS ON EPIDEMIOLOGIC DIAGNOSES OF POSTTRAUMATIC-STRESS-DISORDER

In an epidemiologic study of 641 interviewed subjects in the Australia n Vietnam Veterans Health Study, three diagnoses of Vietnam combat-rel ated posttraumatic stress disorder (PTSD) were obtained: lifetime prev alence using a variant of the Diagnostic Interview Schedule and lifeti me and current (I-month) PTSD prevalence using the Standardized Clinic al interview for the Diagnostic and Statistical Manual of Mental Disor ders, Third Revision, Prevalence estimates using the Standardized Clin ical Interview varied according to interviewer characteristics (female vs. male, clinician vs. nonclinician) but not for the Diagnostic Inte rview Schedule, The authors use a simple variant of logistic regressio n to distill estimates of two informative parameters characterizing in terviewers' judgments: severity threshold(related to the individual in terviewer's criterion of ''caseness'') and reliability (related to deg ree of classification error of the individual interviewers). Examinati on of these estimates shows that female clinicians adopted lower sever ity thresholds for diagnosis of PTSD than other interviewers and hence had higher prevalence estimates while being relatively reliable in th eir judgments. Examination also shows that nonclinician interviewers c an perform at least as reliably as clinicians. The Diagnostic intervie w Schedule measure of PTSD was not moderated by these interviewer aspe cts. This use of threshold and reliability parameters is offered for r outine use in epidemiologic field studies to examine potential intervi ewer effects.