Combining Assessments May Lead to Better Suicide Predictors

A study in BMC Psychiatry suggests that using both the Suicide Intent Scale (SIS) and the Karolinska Interpersonal Violence Scale (KIVS) combined may be better for predicting completed suicide than using them separately. According to the study, “The nonsignificant correlation between the scales indicates that they measure different components of suicide risk.”

Suicide risk assessment is notoriously difficult. One of the strongest risk factors for completed suicide is an earlier suicide attempt. The researchers noted that among hospitalized male suicide attempters with bipolar/unipolar disorder and schizophrenia, almost 25% committed suicide within the year following the suicide attempt. Suicide attempters who had used a violent method showed a very high risk. Suicide risk assessment scales by themselves have a positive predictive value of under 15%. “Complicating the assessment strategy even further is the fact that most studies focus on single risk factors, leaving clinicians and expert panels to estimate how risk factors interact to influence outcomes,” the study authors wrote.

The authors’ previous research noted that the KIVS predicted suicide in suicide attempters. Could that assessment vehicle, in combination with the SIS, better predict future suicidal behavior and attempts?

Patients being treated after a suicide attempt at the Karolinska University Hospital were asked to take part in a study on biological and psychological risk factors for suicidal behavior. Between 1993 and 1998, 81 suicide attempters (35 men and 46 women, mean age 37 years, SD = 12, range 18—69 years) were included in the study from emergency departments and inpatient wards. Inclusion criteria were: a suicide attempt within one month of the evaluation, a minimum age limit of 18 years, and ability to communicate both verbally and in writing in Swedish. Exclusion criteria were: schizophrenia spectrum psychosis, dementia, mental retardation, and intravenous drug abuse.

Seven of 14 patients who had died before April 2013 had committed suicide. The positive predictive value for the Suicide Intent Scale alone was 16.7 %, with a specificity of 52% and an area under the curve of 0.74. A combined assessment with the KIVS gave higher specificity (63%) and a positive predictive value of 18.8% with an AUC of 0.83. Combined use of SIS and KIVS expressed interpersonal violence as an adult subscale gave a sensitivity of 83.3% and a specificity of 80.3%, as well as a positive predictive value of 26% with an AUC of 0.85. The correlation between KIVS and SIS scores was not significant.

“Using both scales, the number of false-positives was reduced by nine patients compared to using SIS alone (26 vs. 35 false-positives) and by 17 patients compared to using KIVS alone (26 vs. 43 false-positives), leading to a specificity of 63%,” the researchers said. “In other words, 11—21% of suicide attempters in this cohort, classified as false-positive high suicide risk patients, could be reclassified as patients with a lower suicide risk after combining both scales in the suicide risk assessment…Theoretically, an optimal prediction model for suicide needs to have high sensitivity to detect all patients at risk for suicide and, if possible, also high specificity to reduce the number of false-positives.”

The researchers noted a unique factor in assessing suicide risk: because suicide is a rare outcome, it is nearly impossible to predict with a degree of accuracy that is clinically meaningful. The findings showed that suicide attempters had a higher risk of violent behavior than suicide ideators, making violent behavior one of the key differences between attempters and ideators. “More well-designed follow-up studies focusing on the usefulness of structured suicide risk assessment scales in high-risk clinical groups are needed,” the researchers concluded.