The Manchester Self Harm Rule had good sensitivity but poor specificity for predicting repeat self harm or suicide
- emergency services (hospital)
- emergency services (psychiatric)
- self injurious behaviour
- suicide (attempted)
Q In patients who present to the emergency department (ED) with self harm, can a simple clinical rule predict repetitions of self harm or suicide in the next 6 months?
prospective cohort study with separate derivation and validation data sets.
5 EDs in Manchester and Salford, UK.
9086 episodes of self harm (intentional self poisoning or self injury) in patients 11–98 years of age (median 30 y, 56% women). Patients who did not wait for assessment or refused treatment were excluded.
Description of prediction guide:
patients were considered to be at moderate or high risk of repeat self harm or suicide if any 1 of the 4 components of the Manchester Self Harm Rule was present: history of self harm, previous psychiatric treatment, benzodiazepine use in this attempt, or current psychiatric treatment.
suicide or repeat visit to the ED for self harm within 6 months of the index ED visit.
In each data set, 78% of patients were classified as having moderate or high risk of repeat self harm or suicide. 17% of patients in the derivation set and 18% in the validation set had repeat ED visits for self harm or died by suicide within 6 months. The diagnostic accuracy of the Manchester Self Harm Rule in the derivation and validation sets is shown in the table. The rule identified all 22 patients who committed suicide within 6 months.
The Manchester Self Harm Rule had good sensitivity but poor specificity for predicting repetitions of self harm or suicide in patients who presented to the emergency department with self harm.
A modified version of this abstract appears in Evidence-Based Medicine.
Predicting suicide risk remains elusive with existing measures.1,2 Cooper et al derived a high sensitivity (94%) clinical prediction tool for assessing self harm risk after an ED visit for self harm. The tool predicted all known cases of subsequent suicide within 6 months. High sensitivity alone is not adequate because the low specificity (25%) of the tool would generate many false positive results, resulting in unnecessary assessment and treatment. Ease of use by non-mental health specialists and excellent case detection ability make this tool a feasible “incremental improvement”3 in suicide risk assessment.
High quality methods were used to derive and validate the prediction tool in a population based sample in the UK. However, 23% of self harm episodes were omitted from the analysis because patients left hospital without having assessment data collected. It is possible that such patients could be more likely to attempt suicide in the future than those who wait to be assessed. It is not known how many included patients had subsequent self harm episodes that were not recorded because of failure to return to an ED participating in the study.
Although the results require validation in other populations and settings, this tool may be clinically useful for screening for self harm risk in ED settings similar to those in the study. However, the potential benefits need to be weighed against the additional resources likely to be consumed by those patients who screen positive, but who, in truth, may not be at increased risk.
For correspondence: Dr J Cooper, Centre for Suicide Prevention, University of Manchester, Manchester, UK.
Sources of funding: Manchester Health Authority, South Manchester University Hospitals NHS Trust, Central Manchester and Manchester Children’s University Hospitals NHS Trust, Pennine Acute NHS Trust, and Mental Health Services of Salford NHS Trust.