The risk of not knowing – A predictive validity study of the “Don't know” scores on a violence screen in acute psychiatry

Access to information about risk factors of violence for patients admitted to acute psychiatric wards may be sparse. This prospective study from three acute wards explored associations between items scored “Don't know” and violence during hospital stays (N ​= ​1435) and the first three months after discharge (N ​= ​461) when using a violence risk screening tool (Violence risk screening - 10; V-RISK-10). When V-RISK-10 was scored at admission and “Don't know” was weighted 0 or 1, the area under the curve of the receiver operating characteristics (AUC) was 0.79 and 0.82 for inpatient violence and 0.79 and 0.80 for post-discharge violence. “Don't know” scored at admission was significantly associated with inpatient violence for eight risk items and with violence after discharge for seven items. Numbers of “Don't know” scores decreased substantially at discharge. A substantial proportion of those scores seemed to change into “Maybe/moderate” or “Yes”. There were some differences in single items in the associations of “Don't know” with violence and the distribution of scores. Findings indicate that items scored “Don't know” at the time of admission may be associated with violence during hospital stay and after discharge. More research is needed to elaborate these findings.