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Securing a diagnosis in patients presenting with suspected paracetamol (acetaminophen) poisoning: A retrospective cohort study.

BACKGROUND
Paracetamol (acetaminophen) is the most commonly ingested drug in self-poisoning. The correlation between an ingested self-reported dose of paracetamol and plasma paracetamol concentration is moderate. The usefulness of this correlation to rule out paracetamol ingestion has to be investigated. The objective of this study is to evaluate the performance of medical history in diagnosis of paracetamol ingestion in patients admitted to the Emergency Department (ED) for deliberate self-poisoning.


MATERIALS AND METHODS
This retrospective cohort study was carried out in two EDs at an urban university hospital in Toulouse, France, from January 1 to June 30, 2018. All patients older than 15 years of age attending the ED for suspected deliberate self-poisonings who underwent blood testing were included. Medical history was considered positive for paracetamol intoxication if patients directly reported the use of paracetamol for deliberate self-poisoning during their ED admission or if paramedics reported the presence of paracetamol packages at the patient's home. We defined paracetamol ingestion as any concentration of paracetamol > 5 mg/L measured on presentation.


RESULTS
We included 709 patients. 151 (21%) patients had a positive plasma paracetamol concentration. 165 (23%) patients revealed a positive medical history in terms of paracetamol ingestion. 29 (4%) patients had a false-negative medical history, and 45 (6%) patients had a false-positive history. The sensitivity of the medical history (95% confidence interval) was 79% (72 - 87), and its specificity was 92% (89 - 94).


CONCLUSION
Diagnosis of self-poisoning involving paracetamol cannot be made using patient's medical history alone. Screening for paracetamol intoxication is proposed.