Version 0.1 – June 2019
OxMIV is a web-based risk calculator for assessing risk of violent offending in individuals with a diagnosis of severe mental disorder (schizophrenia spectrum or bipolar disorder). This tool was developed by the Forensic Psychiatry and Psychology group at the University of Oxford and is available on the OxRisk.com website.
How was it developed?
OxMIV was derived and externally validated in Sweden, using data from a national cohort of 75158 individuals aged 15-65 years with a diagnosis of severe mental illness (schizophrenia spectrum or bipolar disorder) between 2001 and 2008. Potential predictive variables for inclusion in OxMIV were drawn from carefully reviewing the evidence on previous history of violence, sociodemographic, family, and clinical factors, and considering only those that were both reliable risk factors and relatively easy to score.
First, the OxMIV model was derived using the data from 58771 patients, and 16 mostly routinely collected criminal history, sociodemographic, family, and clinical factors were included in the final model. Then, the model was externally validated in a distinct group of 16387 patients to establish its performance in a new sample. The model generates a simple risk calculator (OxMIV) that generates one output – category (low, increased) and probability scores (%) based on 12 month violent offending.
The research behind OxMIV has been peer-reviewed and published in the Lancet Psychiatry journal (Open Access). OxMIV has also been externally validated in a different setting, a psychiatric ward of a German prison hospital and the validation paper is published in Frontiers in Psychiatry. Further validations in other countries are planned. For a full bibliography related to OxMIV, visit the OxRisk.com website.
When should OxMIV be used for?
OxMIV is designed to predict violent offending within 12 months in individuals with a diagnosis of severe mental illness (schizophrenia spectrum or bipolar disorder).
Who should use OxMIV?
Healthcare staff can use the OxMIV tool, as scoring to specific cases requires interpretation of some of the predictor variables. Individuals who use OxMIV are encouraged to read other background literature (including the published papers about OxMIV, all freely available on OxRisk.com) and any training videos developed locally within individual countries.
How should the outputs be interpreted?
The outputs from the OxMIV calculator include probability scores for violent offending within 12 months. This can be used as an adjunct to full clinical assessment. A probability of 5% for 12 months means that, on average, 5 in 100 individuals with the same predictors will commit violent crime over the next 12 months. This is a similar interpretation to the chance of rain in a weather app – so a 10% chance of rain at a certain time will mean that on 10 days with the same characteristics, it will rain on one occasion. The calculator also provides a risk category, based on pre-specified risk levels identified on the calculator (Low: <5%; Increased:≥5%). This cut-off was chosen based on epidemiological evidence of the average rate of a violent crime over 1 year period in individuals with schizophrenia-spectrum and bipolar disorders. The maximum score is 20%. The tool has a high negative predictive value (99.5%) – in other words, of 200 individuals identified as low risk by the tool, 199 did not offend violently within in 1 year. This suggests that the tool can be very helpful in screening out low risk people. Therefore, using this in combination with clinical judgement can assist in decisions such as resource allocation and safety planning.
How should each item be scored?
See item descriptions on the scoring sheet. The best and most recent source of information should be used if possible. Some variables can be scored as unknown, and OxMIV will display risk ranges to reflect this uncertainty.