The InterSePT scale for suicidal thinking reliability and validity.
BACKGROUND
The InterSePT Scale for Suicidal Thinking (ISST) is a 12-item instrument for the assessment of current suicidal ideation in patients with schizophrenia and schizoaffective disorders. We report the psychometric characteristics of this new scale based on two studies.


METHODS
In Study 1, 22 inpatients with schizophrenia and schizoaffective disorders, who had recently attempted suicide or engaged in suicidal ideation, were rated by three trained independent raters to examine interrater reliability. In Study 2, a total of 980 patients with schizophrenia or schizoaffective disorder with a history of suicidal ideation in the past 36 months were enrolled in a 2-year industry-sponsored suicide prevention study. At baseline, these patients were administered the ISST and the Clinical Global Impression Scale for Severity of Suicidality (CGI-SS) by the Principal Investigator (PI) and by a blinded rater (BR), who also administered the Positive and Negative Symptom Scale (PANSS), the Calgary Depression Scale (CDS), and the Scale of Functioning (SOF). Indices of internal reliability, construct and discriminant validity were examined.


RESULTS
The intraclass correlation coefficient (ICC) for the total ISST score for the 22 subjects in Study 1 was 0.90 and mean weighted item kappa coefficients ranged from 0.66 to 0.92. In Study 2, internal reliability (Cronbach alpha) was high, ranging from 0.86 to 0.89 for the individual items, and the overall Cronbach alpha coefficient for all items was 0.88. The ISST (PI) total score was highly correlated with the CGI-SS by the blind rater (r = 0.61, p < 0.0001). ISST total scores significantly differentiated the different levels of CGI-SS (F = 519.2; p < 0.0001). Results of construct and discriminant validity analyses are also presented.


CONCLUSIONS
The ISST is a reliable and valid instrument for the assessment of current suicidal thinking in patients with schizophrenia and schizoaffective disorder by both clinicians and researchers.
Lindenmayer
J P
JP
New York University School of Medicine, New York, NY, USA. lindenmayer@nki.rfmh.org
Czobor
Pal
P
Alphs
Larry
L
Nathan
Ann-Marie
AM
Anand
Ravi
R
Islam
Zahur
Z
Chou
James C Y
JC
D000293:Adolescent; D000328:Adult; D000339:Affect; D003863:Depression / Q000175:diagnosis; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011594:Psychometrics; D011618:Psychotic Disorders / Q000175:diagnosis / Q000523:psychology; D015203:Reproducibility of Results; D012559:Schizophrenia / Q000175:diagnosis; D012565:Schizophrenic Psychology; D012720:Severity of Illness Index; D013406:Suicide, Attempted / Q000517:prevention & control / Q000706:statistics & numerical data*; D011795:Surveys and Questionnaires; D013850:Thinking