title: Reliability of the reported ingested dose of acetaminophen for predicting the risk of toxicity in acetaminophen overdose patients.
abstract: OBJECTIVE
  The present study examines the relationship between the dose of acetaminophen reported to have been ingested by patients and the occurrence of serum acetaminophen levels above the 'possible toxicity' line in patients presenting at the hospital after acetaminophen overdose. The prognostic value of patient-reported dosage cut-offs of 8, 10 and 12 g was determined.
  
  
  METHODS
  This retrospective cohort study included patients admitted to the emergency department or hospital within 24 hours of acetaminophen ingestion. Serum acetaminophen concentrations were considered to be the gold standard, and specificity, sensitivity and positive/negative predictive values were calculated from the reported ingested dose, to predict toxicity using the Rumack-Matthew nomogram (i.e. the 'possible toxicity' treatment line) and standard equations.
  
  
  RESULTS
  Of 305 patients identified, 291 met the study inclusion criteria, and 121 (41.6%) had serum acetaminophen concentrations above the 'possible toxicity' treatment line. The range of patient-reported acetaminophen ingested was 1-75 g, with 185 patients (63.6%) reporting ≥8 g. One hundred eighteen patients (97.5%) who reported ingesting ≥8 g had serum acetaminophen concentrations above the '150-line', compared with only three patients (2.5%) who reported ingesting <8 g (p < 0.001). The positive predictive value of a patient-reported dose ≥8 g for predicting serum acetaminophen concentrations above the 'possible toxicity' treatment line was 63.78%, with a negative predictive value of 97.17%. The sensitivity of patient-reported doses ≥8 g was high (97.52%) but with low specificity (60.59%). The sensitivity of patient-reported doses ≥10 g also was high (89.26%) with low specificity (65.29%), whereas the sensitivity of ≥12 g dose was low (61.16%) with high specificity (86.47%).
  
  
  CONCLUSIONS
  Patient-reported doses of acetaminophen are good risk indicators for acetaminophen overdose patients in Malaysia. Patient-reported ingestion of ≥8 g (as a cut-off dose) had a higher sensitivity than ≥10 g or ≥12 g. The results of this study have important implications for toxicity risk evaluations in areas with poor serum acetaminophen assay availability.
authors.affiliation: WHO Collaborating Centre for Drug Information, National Poison Centre, Universiti Sains Malaysia, Penang, Malaysia. saedzyoud@yahoo.com
authors.forename: Sa'ed H
authors.initials: SH
authors.lastname: Zyoud
authors.forename: Rahmat
authors.initials: R
authors.lastname: Awang
authors.forename: Syed Azhar Syed
authors.initials: SA
authors.lastname: Sulaiman
mesh_terms: D000082:Acetaminophen / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000506:poisoning*; D018712:Analgesics, Non-Narcotic / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000506:poisoning*; D015331:Cohort Studies; D004305:Dose-Response Relationship, Drug; D062787:Drug Overdose; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008296:Malaysia; D008297:Male; D049451:Nomograms; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D018712:Analgesics, Non-Narcotic; D000082:Acetaminophen