Serum lactate dehydrogenase (LDH) activity was greater in the nonsurvivors of acetaminophen-induced acute liver failure than the survivors. Total LDH activity and alanine aminotransferase (ALT) were measured in serum from all nonsurvivors (n = 30) and survivors (n = 28) on study days 1 and 3. Model for end-stage liver disease (MELD) scores were also obtained when available (n = 20 for survivors and 29 for nonsurvivors). A, LDH activity on day 1. B, LDH activity on day 3. C, Receiver operating characteristic (ROC) curves for LDH, ALT, and MELD score on day 1. Area under the curve (AUC) values are displayed in the bottom right corner. D, ROC curves for LDH, ALT, and MELD score on day 3. AUC values are displayed in the bottom right corner. Differences in AUC values for MELD-LDH versus MELD and MELD-LDH versus LDH were statistically significant (p < .05) on day 3. Boxes show the 25th to 75th percentiles. Whiskers show the 10th and 90th percentile values. Lines show median values. Dots represent outliers.