CLINICAL HANDBOOK OF SCHIZOPHRENIA

498 VI. SPECIAL POPULATIONS AND PROBLEMSSuicide Assessment MeasuresMonitoring of suicide risk can be enhanced by thoughtful use of standardized measureswith acceptable reliability and validity for individuals with schizophrenia. Research supportsthe assessment of suicide ideation among psychotic patients; however, a paucity ofclinical measures exists assessing suicide risk specifically in schizophrenia. Rating scalesfor assessing suicide risk in schizophrenia include the Schizophrenia Suicide Risk Scale(SSRS; Taiminen et al., 2001) and the InterSePT Scale for Suicidal Thinking (ISST;Lindenmayer et al., 2003). The 25-item SSRS, developed as a semistructured tool for estimatingshort-term risk for suicide, includes 13 “History items” assessing demographicand clinical variables derived from a psychological autopsy study of suicide in schizophrenia,items assessing clinical severity, and items derived from the Calgary DepressionScale, given the high risk for suicide among depressed individuals with schizophrenia.The Interview items have acceptable interrater reliability among living respondents(kappa = .79, SD = 0.30) but poor reliability when completed using all-source data,including collateral records and interviews with informants of individuals who died bysuicide (kappa = .31, SD = 0.45). The History items also had unacceptably low internalconsistency for both the living (Cronbach’s alpha = .54) and the deceased groups(Cronbach’s alpha = .38). SSRS total scores, and History and Interview subscales significantlydifferentiated living respondents with schizophrenia from those who died by suicide.Acceptable sensitivity and specificity could not be demonstrated for any SSRS cutscore in predicting risk for suicide; however, scores above 36 out of a total possible 90points yielded poor sensitivity (32%) and only a marginal negative predictive value(59%), despite strong specificity (97%) and a strong positive predictive value (92%). Thescale’s authors concluded that “the SSRS seems not to be a practical screening instrumentfor suicide risk in schizophrenia, and it is probably impossible to construct a suicide riskscale with both high sensitivity and high specificity in this disorder” (Taiminen et al.,2001; p. 199).The ISST was developed for use as a primary outcome measure in the InternationalSuicide Prevention Trial (InterSePT; Meltzer et al., 2003). The ISST is a 12-item versionof the 19-item Scale for Suicide Ideation, developed by deleting items with low item–totalcorrelations or redundancy, or judged to be difficult to interpret based on the findings ofa factor analysis, and adding an item assessing delusions or hallucinations of self-harm.An initial investigation of the interrater reliability of the ISST with 22 patients yielded astrong intraclass correlation coefficient (ICC = .90) and a mean weighted kappa of .77(SD = 1.0). A subsequent validation study with 980 study patients yielded strong internalconsistency for the ISST items for the principal investigator (range: alpha = .86–.89) andfor a blinded rater (range: alpha = .88–.90), with a total scale alpha of .88. A factor analysisyielded a three-factor model, representing “Current Suicidal Thinking,” “VolitionalSuicidal Thinking,” and “Cause of Suicidal Thinking,” together explaining 55.2% of thetotal variance in ISST scores. Criterion validity was demonstrated by significant associationsbetween ISST scores and measures of suicide ideation and depression; convergentvalidity, by associations with measures of symptom severity and substance misuse; anddiscriminant validity, by differentiating between study patients with higher versus lowerlevels of suicidality. Research is needed to assess the predictive validity of the ISST andother measures of suicide risk in schizophrenia with respect to future suicidal ideationand behavior, and as a treatment outcome measure.Clinicians wishing to use standardized psychological assessment instruments shouldhave appropriate training and clinical experience in the selection, administration, scoring,and interpretation of such measures. Unsophisticated or otherwise ineffective use of