Development of a Computerized Adaptive Test Suicide Scale-The CAT-SS

Abstract

Objective: Current suicide risk screening and measurement are inefficient, have limited measurement precision, and focus entirely on suicide-related items. For this study, a psychometric harmonization between related suicide, depression, and anxiety symptom domains that provides a more balanced and complete spectrum of suicidal symptomatology was developed. The objective of this article is to describe the results of the early stages of computerized adaptive testing development for a suicide scale and pave the way for the final stage of validation.

Methods: Data from psychiatric outpatients at the University of Pittsburgh and a community health clinic were collected from January 2010 through June 2012. 789 participants were enrolled in the calibration phase; 70% were female, and 30% were male. The rate of major depressive disorder as diagnosed by DSM-5 was 47%. The item bank contained 1,008 items related to depression, anxiety, and mania, including 11 suicide items. Data were analyzed using a bifactor model to identify a core dimension between suicidal ideation, depression, anxiety, and mania items. A computerized adaptive test was developed via simulation from the actual complete item responses in 308 subjects.

Results: 111 items were identified that provided an extension of suicidality assessment to include statistically related responses from depression and anxiety domains that are syndromally associated with suicidality. All items had high loadings on the primary suicide dimension (average = 0.67; range, 0.49-0.88). Analyses revealed that a mean of 10 items (5-20) had a correlation of 0.96 with the 111-item scale, with a precision of 5 points on a 100-point scale metric. Preliminary validation data based on 290 clinician interviews revealed a 52-fold increase in the likelihood of current suicidal ideation across the range of the Computerized Adaptive Test Suicide Scale (CAT-SS).

Conclusions: The CAT-SS is able to accurately measure the latent suicide dimension with a mean of 10 items in approximately 2 minutes. Further validation against an independent clinician-administered assessment of suicide risk (ideation and attempts) and prediction of suicidal behavior is underway.

Figure 1.. Finite Mixture Distribution for Estimated Scores on the 11-item Suicide Scale^a

^aA mixture of 2 normal distributions with different means (normal and elevated), pooled standard deviation, and different mixing proportions. The high suicidal ideation component distribution has an elevated mean containing 45% of the sample. The smooth curves are the 2 estimated normal distributions, and the vertical lines represent the histogram (observed frequency distribution) of the estimated scores.

Figure 2.. Finite Mixture Distribution for Final CAT-SS Scores^a

^aA mixture of 3 normal distributions with different means (none, mild, and elevated), pooled standard deviation, and different mixing proportions. The high suicidal propensity component distribution has an elevated mean containing 14% of the sample, 56% are in the intermediate group (ie, mild ideation or depression and anxiety precursors), and 30% had no evidence of suicidal thoughts or propensity. The smooth curves are the 3 estimated normal distributions, and the vertical lines represent the histogram (observed frequency distribution) of the estimated scores. Abbreviation: CAT-SS = Computerized Adaptive Test Suicide Scale.