Patient perceptions of the potential lethality associated with deliberate self-poisoning

Little is known about patient perceptions of the lethality of their overdose. Our aim was to compare patient perceptions with the risk assessment of clinical toxicologists.

A prospective observational study of overdose patients presenting to a tertiary hospital. Eligible patients were surveyed once they were medically fit for psychiatric evaluation. Descriptive data were collected, including the Pierce Suicide Intent Scale (SIS). In response to 'how dangerous did you think this overdose was when you took the tablets?' patients marked a 10 cm VAS, with 0 = would be harmless, 10 = certain to cause death. A panel of clinical toxicologists independently made a risk assessment on a 10 cm VAS, with 0 = non-toxic ingestion and 10 = uniform lethality even with full medical intervention.

Of 202 patients enrolled, 118 (58.4%, 95% CI 51-65) were female; median age 33 years (interquartile range [IQR] 24-42). One hundred and three (51%, 95% CI 44-58) stated it was their intention to kill themselves and 44 (21.8%, 95% CI 16-28) wrote a suicide note. They most commonly used their own prescription medications (141, 69.8%, 95% CI 63-76). The median patient visual analog scale (VAS) was 5.8 (IQR 2.3-8.3) and median toxicology VAS was 1.4 (IQR 0.6-2.8); this difference was statistically significant (P < 0.0001). The correlation between the patient visual analog scale (VAS) and Pierce SIS (median 8.5/25 [IQR 4-12]) was strong (r= 0.73, P < 0.0001).

Patient perceptions of the lethality of their overdose are correlated with their suicidal intent as measured on the Pierce SIS, with a significant mismatch between patient perceptions and the toxicological risk assessment.