title: A manic-depressive symptom self-report in optical scanable format.
abstract: BACKGROUND
  The Internal State Scale (ISS) is a self-report instrument that allows the simultaneous assessment of both manic and depressive symptoms in individuals with manic-depressive disorder. Prior work indicates that subscales are highly correlated with clinician ratings of mania and depression and provide a discriminant function that identifies individuals in manic/hypomanic, mixed, depressed, and euthymic mood states. A drawback to the ISS is that its items were developed in the visual analogue scale (VAS) format which is labor-intensive to score, particularly with repeat (e.g. daily) administration. A Likert-based format would allow quick and easy optical scanning for which scoring could be automated.
  
  
  METHODS
  To compare discriminating properties in Likert versus VAS format we re-analyzed previously collected data and collected new data: (a) VAS-based ISS scores from 86 subjects from a prior four-site study were re-analyzed by collapsing scores into 20 and then 10 Likert-based bins to assess loss of precision from collapsing scores, and (b) 24 additional subjects were administered the ISS in VAS and Likert formats to assess loss of precision due to instrument completion factors.
  
  
  RESULTS
  Discriminant ability, including kappas and receiver operator characteristic curves, were unchanged across the two formats. Within-subjects reliability was uniformally high across formats.
  
  
  CONCLUSIONS
  Likert-based scoring of the ISS can be used without loss of precision, thus making automated scoring of the ISS feasible. This format will be particularly useful for studies that require processing of large numbers of ISSs, such as those that collect frequent ratings over long periods of time and/or those that utilize large samples.
authors.affiliation: Division of General Medicine and the Leonard Davis Institute of Health Economics, University of Pennsylvania, Philadelphia, USA.
authors.forename: Henry A
authors.initials: HA
authors.lastname: Glick
authors.forename: Linda
authors.initials: L
authors.lastname: McBride
authors.forename: Mark S
authors.initials: MS
authors.lastname: Bauer
mesh_terms: D001714:Bipolar Disorder / Q000145:classification / Q000175:diagnosis* / Q000453:epidemiology; D003937:Diagnosis, Differential; D001330:Electronic Data Processing; D005260:Female; D006801:Humans; D008297:Male; D010147:Pain Measurement; D011237:Predictive Value of Tests; D011569:Psychiatric Status Rating Scales; D011594:Psychometrics; D012372:ROC Curve; D015203:Reproducibility of Results; D012647:Self-Assessment; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index