Mania in the Swedish Twin Registry: criterion validity and prevalence

Authors


  • Department of Genetics, CB#7264, 4109D Neuroscience Research Building, University of North Carolina, Chapel Hill, NC 27599-7264, US. Email: pfsulliv@med.unc.edu

    Federico Soldani, Associate in Psychiatry

    Department of Psychiatry, Harvard University, Boston, MA, US

    Nancy L. Pedersen, Professor

    Department of Medical Epidemiology and Biostatistics, Karolinska Institute, Stockholm, Sweden

Patrick F. Sullivan, Professor (Correspondence)

Abstract

Background:  In population surveys, the assessment of mania is commonly done by trained lay interviewers using structured diagnostic instruments: the validity of this approach has been questioned. We examined the criterion validity and prevalence of lifetime mania in a survey of Swedish twins conducted with interview methodology usually applied in psychiatric epidemiology.

Methods:  41 838 individuals in the Swedish Twin Registry were evaluated via a telephone interview that included the eight DSM-IV mania items, and these data were merged with inpatient hospitalization discharge diagnoses from two comprehensive national registries (the criterion). An algorithm with eight cut-points was used to diagnose lifetime mania, and compared by a receiver operator characteristic curve to the criterion. The algorithm requiring at least four positive items resembling a DSM-IV diagnosis.

Results:  History of hospitalization for a psychiatric condition that included a manic episode was present for 0.7% of all living twins, and predicted non-response to the survey (OR = 0.5; 95% CI = 0.4−0.6). The incidence rate for first hospitalization was 2.1/10 000 year−1. For ≥1 symptom (first cut-point), the prevalence, sensitivity and specificity were 3.6%, 39.0% and 96.6%; for ≥ 4 symptoms (DSM-IV-like cut-point) 2.6%, 36.5% and 97.6%; and for eight symptoms 0.3%, 18.0% and 99.8%. Positive predictive values were, respectively, 5.5%, 7.0% and 29.8%.

Conclusions:  The performance of the telephone screening for mania by lay interviewers in terms of positive predictive power was not satisfactory; despite a high specificity, the false positive rate was high. The low population prevalence of mania, non-response bias, criterion choice and inherent limitations of the interviewing method are among the explanations. Assessment of a lifetime manic episode based on lay interviewer screening may yield misleading data.

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