Predicting acute acetaminophen hepatotoxicity with acetaminophen- aminotransferase multiplication product and the Psi parameter

Context. Prediction of potential hepatotoxicity is important for individualizing therapy with N-acetylcysteine (NAC) in patients with acute acetaminophen overdose. Acetaminophen-aminotransferase multiplication product (APAP × AT) and the Psi Parameter (Psi) have been reported to be the predictors of acetaminophen hepatotoxicity. Objective. To determine the validity of APAP × AT and Psi in predicting hepatotoxicity secondary to acute acetaminophen overdose. Materials and methods. We retrospectively reviewed acute acetaminophen overdose cases who were treated with NAC at Siriraj Hospital, Thailand during January 2004-June 2012. The patients' ages were 12 years or more. Initial acetaminophen concentration (mg/L) and aminotransferase (IU/L) were multiplied to obtain APAP × AT. Psi were derived from initial acetaminophen concentrations (mg/L) and lag time (hours) to NAC therapy. The cut-off values for APAP × AT and Psi were 1500 mgâ̂™IU/L and 5 mMâ̂™h, respectively. Hepatotoxicity (defined as aspartate or alanine aminotransferase (ALT) greater than 1000 IU/L) was the outcome of interest. Results. A total of 255 patients were included, 32 of whom developed hepatotoxicity. APAP × AT had sensitivity, specificity, and negative likelihood ratio of 90.6%, 62.8%, and 0.2, respectively. The sensitivity of Psi, specificity, and negative likelihood ratio were 96.9%, 91.5%, and 0.0, respectively. The areas under the curve of the receiver operating characteristic (ROC) curve for APAP × AT and Psi were 0.82 and 0.96, respectively, with a statistically significant difference between the two methods (p = 0.002). APAP × AT showed higher specificity (92.5%) in patients who presented 8-24 h after the overdose. Discussion and conclusion. Psi and APAP × AT are valid clinical tools in predicting hepatotoxicity secondary to acute acetaminophen overdose in adults. APAP × AT is useful in predicting a low likelihood of hepatotoxicity after standard NAC therapy among late-presenting patients.