Reliability of history of acetaminophen ingestion in intentional drug overdose patients.

The objective of this study was to determine the reliability of denial of acetaminophen ingestion in intentional drug overdose patients. All intentional drug overdose patients admitted to an emergency department who were able to provide a history were included. A detailed history was obtained on names, timing and number of medications ingested, and serum acetaminophen was assayed. Multidrug ingestion was defined as the reporting of ≥2 medications. Patients were considered 'reliable' if they reported acetaminophen ingestion and had detectable acetaminophen levels or the other way around. Validity parameters of acetaminophen history were assessed by sensitivity, specificity and positive and negative predictive values. A total of 154 patients were included. History was significantly more reliable in patients who denied ingestion of acetaminophen (n = 107) compared with patients who reported it (n = 47; 95.3% vs 65.9%, respectively; p < 0.0001, 95% CI of the difference 17.5%-41.2%). No suicidal patient who denied both acetaminophen and multidrug ingestions had a detectable acetaminophen level (negative predictive value 1, 95% CI 0.93-1.0). It is suggested that denial of both acetaminophen and multidrug ingestions by intentional drug overdose patients after a thorough history taking can be considered reliable for acetaminophen history. In facilities with limited resources, these patients may not require routine acetaminophen screening.