Reported ingested dose of paracetamol as a predictor of risk following paracetamol overdose.

Abstract

To evaluate reported ingested dose of paracetamol as a risk assessment tool in acute paracetamol overdose. Data was retrospectively obtained from a clinical toxicology database linked to one Australian and two United Kingdom hospitals. Plasma paracetamol concentrations (PPCs) of adult patients presenting with acute single ingestion, non-staggered paracetamol deliberate self-poisoning between 2006 and 2012 were recorded and plotted on a treatment nomogram to determine accuracy of reported dose ingested as an indicator for antidotal treatment. PPC plotted on a treatment nomogram with a line intersecting a 4-h concentration of 100mg/L [667μmol/L] was considered an indication for antidotal treatment in the UK; the corresponding Australasian population utilised a line intersecting 150mg/L [1000μmol/L]. Of 1246 patients, 65.7% were female and 88% were from the UK. Fifty-two percent of patients reporting ingestion of ≥8g paracetamol had a PPC above the 100mg/L treatment line; PPV 52% [95% confidence interval (CI) 49%, 55%], sensitivity 81% [95%CI 78%, 85%]. Forty-four of patients reporting percent ingestion of ≥10g had a PPC above the 150mg/L treatment line; PPV 44% [95% CI 41%, 49%], sensitivity 85% [95% CI 78%, 89%], 72% of patients reporting ingestion of ≥16g had a PPC above the 100mg/L treatment line; PPV 72% [95% CI 67%, 77%], sensitivity 50% [95% CI 45%, 54%]. Overall, there was moderate correlation (R = 0.58) between reported paracetamol dose ingested and extrapolated 4-h PPC. There is a positive correlation between reported ingested dose of paracetamol and subsequent chance of a PPC being above a defined treatment line; however, ingested dose of paracetamol alone is a poor risk assessment tool in accurately determining need for treatment with an antidote.