Under-reporting and Poor Adherence to Monitoring Guidelines for Severe Cases of Isoniazid Hepatotoxicity.

BACKGROUND & AIMS: Isoniazid is a leading cause of liver injury but it is not clear how many cases are reported or how many clinicians and patients adhere to American Thoracic Society (ATS) guidelines. We collected data on cases of isoniazid hepatotoxicity and assessed adherence to ATS guidelines and reports to the Centers for Disease Control's (CDC) isoniazid severe adverse events program. METHODS: We analyzed Drug-Induced Liver Injury Network (DILIN) cases considered definite, highly likely, or probable for isoniazid injury from 2004 through 2013. We assessed the delays in isoniazid discontinuance according to ATS criteria and hepatotoxicity severity by Severity Index Score. We checked reporting to the CDC by matching cases based on age, latency, indication, reporting period, and comorbidities. RESULTS: Isoniazid was the second most commonly reported agent in the DILIN, with 69 cases; 60 of these met inclusion criteria. The median age of cases was 49 years (range, 4-68 y), 70% were female, 97% had latent tuberculosis, and 62% were hospitalized. Patients took a median of 9 days to stop taking isoniazid (range, 0-99 days). Thirty-three cases (55%) continued taking isoniazid for more than 7 days after the ATS criteria for stopping were met. Twenty-four cases (40%) continued isoniazid for more than 14 days after meeting criteria for stopping. A delay in stopping was associated with more severe injury (P < .05). Of 13 patients who died or underwent liver transplantation, 9 (70%) continued taking isoniazid for more than 7 days after meeting criteria for stopping. Only 1 of 25 cases of isoniazid hepatotoxicity eligible for reporting to the CDC was reported. CONCLUSIONS: Poor adherence to ATS guidelines is common in cases of hepatotoxicity and is associated with more severe outcomes including hospitalization, death, and liver transplantation. Isoniazid continues to be a leading cause of DILI in the United States, and its hepatotoxicity is under-reported significantly.

Acute Liver Failure Due to Acetaminophen Poisoning in Patients With Prior Weight Loss Surgery: A Case Series.

GOALS: To identify an association between prior weight loss surgery (WLS) and acetaminophen-induced acute liver failure (ALF). BACKGROUND: WLS, which has increased in proportion to the global rise of obesity, alters the absorption and metabolism of many drugs including acetaminophen (APAP) and may predispose to toxicity. No study has identified an association between prior WLS and APAP-ALF. STUDY: We retrospectively reviewed a cohort of patients who presented to our center with ALF. We identified 101 patients who presented to our center with ALF between January 2009 and December 2011. All patients were prospectively enrolled into a database using consensus criteria. A history of WLS was obtained through a retrospective chart review. RESULTS: Fifty-four patients (53.5%) had APAP-ALF and 47 (46.5%) had ALF caused by other etiologies. A prior history of WLS was present in 9 of the 54 patients with APAP-ALF versus 0 of the 47 with non-APAP-ALF (P=0.003). Patients with APAP-ALF and prior WLS did not have higher rates of factors commonly associated with APAP overdose, including depression, alcohol abuse, intent to cause self-harm, or use of APAP-narcotic combination drugs. CONCLUSIONS: A history of WLS may predispose to hepatotoxicity and ALF caused by acetaminophen.

Reliability of causality assessment for drug, herbal and dietary supplement hepatotoxicity in the Drug-Induced Liver Injury Network (DILIN).

BACKGROUND & AIMS: Because of the lack of objective tests to diagnose drug-induced liver injury (DILI), causality assessment is a matter of debate. Expert opinion is often used in research and industry, but its test-retest reliability is unknown. To determine the test-retest reliability of the expert opinion process used by the Drug-Induced Liver Injury Network (DILIN). METHODS: Three DILIN hepatologists adjudicate suspected hepatotoxicity cases to one of five categories representing levels of likelihood of DILI. Adjudication is based on retrospective assessment of gathered case data that include prospective follow-up information. One hundred randomly selected DILIN cases were re-assessed using the same processes for initial assessment but by three different reviewers in 92% of cases. RESULTS: The median time between assessments was 938 days (range 140-2352). Thirty-one cases involved >1 agent. Weighted kappa statistics for overall case and individual agent category agreement were 0.60 (95% CI: 0.50-0.71) and 0.60 (0.52-0.68) respectively. Overall case adjudications were within one category of each other 93% of the time, while 5% differed by two categories and 2% differed by three categories. Fourteen per cent crossed the 50% threshold of likelihood owing to competing diagnoses or atypical timing between drug exposure and injury. CONCLUSIONS: The DILIN expert opinion causality assessment method has moderate interobserver reliability but very good agreement within one category. A small but important proportion of cases could not be reliably diagnosed as ≥50% likely to be DILI.

Hepatic histological findings in suspected drug-induced liver injury: systematic evaluation and clinical associations.

UNLABELLED: Drug-induced liver injury (DILI) is considered to be a diagnosis of exclusion. Liver biopsy may contribute to diagnostic accuracy, but the histological features of DILI and their relationship to biochemical parameters and outcomes are not well defined. We have classified the pathological pattern of liver injury and systematically evaluated histological changes in liver biopsies obtained from 249 patients with suspected DILI enrolled in the prospective, observational study conducted by the Drug Induced Liver Injury Network. Histological features were analyzed for their frequency within different clinical phenotypes of liver injury and to identify associations between clinical and laboratory findings and histological features. The most common histological patterns were acute (21%) and chronic hepatitis (14%), acute (9%) and chronic cholestasis (10%), and cholestatic hepatitis (29%). Liver histology from 128 patients presenting with hepatocellular injury had more severe inflammation, necrosis, and apoptosis and more frequently demonstrated lobular disarray, rosette formation, and hemorrhage than those with cholestasis. Conversely, histology of the 73 patients with cholestatic injury more often demonstrated bile plugs and duct paucity. Severe or fatal hepatic injury in 46 patients was associated with higher degrees of necrosis, fibrosis stage, microvesicular steatosis, and ductular reaction among other findings, whereas eosinophils and granulomas were found more often in those with milder injury. CONCLUSION: We describe an approach for evaluating liver histology in DILI and demonstrate numerous associations between pathological findings and clinical presentations that may serve as a foundation for future studies correlating DILI pathology with its causality and outcome.

Limited contribution of common genetic variants to risk for liver injury due to a variety of drugs.

BACKGROUND AND AIMS: Drug-induced liver injury (DILI) is a serious adverse drug event that is suspected to have a heritable component. We carried out a genome-wide association study of 783 individuals of European ancestry who experienced DILI due to more than 200 implicated drugs. METHODS: DILI patients from the US-based Drug-Induced Liver Injury Network (n=401) and three international registries (n=382) were genotyped with the Illumina 1Mduo BeadChip and compared with population controls (n=3001). Potential associations were tested in 307 independent Drug-Induced Liver Injury Network cases. RESULTS: After accounting for known major histocompatibility complex risk alleles for flucloxacillin-DILI and amoxicillin/clavulanate-DILI, there were no genome-wide significant associations, including in the major histocompatibility complex region. Stratification of DILI cases according to clinical phenotypes (injury type, latency, age of onset) also did not show significant associations. An analysis of hepatocellular DILI (n=285) restricted to 193 single-nucleotide polymorphisms previously associated with autoimmune disease showed a trend association for rs7574865, in the vicinity of signal transducer and activator of transcription 4 (STAT4) (P=4.5×10(-4)). This association was replicated in an independent cohort of 168 hepatocellular DILI cases (P=0.011 and 1.5×10(-5) for combined cohorts). No significant associations were found with stratification by other clinical or demographic variables. CONCLUSION: Although not significant at the genome-wide level, the association between hepatocellular DILI and STAT4 is consistent with the emerging role of the immune system in DILI. However, the lack of genome-wide association study findings supports the idea that strong genetic determinants of DILI may be largely drug-specific or may reflect rare genetic variations, which were not assessed in our study.

Drug-induced liver disease.

Drug-induced liver injury (DILI), also known as hepatotoxicity, refers to liver injury caused by drugs or other chemical agents, and represents a special type of adverse drug reaction. It has been estimated that more than 600 drugs and chemicals have been associated with significant liver injury. Many previous reviews have focused on DILI pathogenesis or have outlined the clinical features of liver injury linked to different drugs. This article briefly touches on several areas that are potentially vexing for both the novice and cognoscenti, with the goal of guiding the consultant through one of the most challenging areas of hepatology.

Adaptive ability, behavior and quality of life pre and posttraumatic brain injury in childhood.

CONTEXT: Traumatic brain injury (TBI) is a common, acquired childhood disability, which has been shown to have a significant impact on children's cognitive and educational function. While behavioral problems are also noted, there is ongoing debate about the contribution of preinjury factors in this domain. Few studies have attempted to measure the impact of these preinjury functions on postinjury behavior. OBJECTIVE: To compare pre and postinjury adaptive ability, behavior, executive function and quality of life (QOL) and to identify factors that contribute to outcomes in these domains including injury severity, socio-demographic and preinjury characteristics. DESIGN: Consecutive recruitments to a prospective, longitudinal study, utilizing a between factor design, with injury severity as the independent variable. PARTICIPANTS AND METHODS: Children admitted to hospital with a diagnosis of TBI aged between 6 and 14 years (n = 205) were divided according to injury severity (mild, moderate and severe). Adaptive behavior (Vineland Adaptive Behavior Scales), child behavior (Child Behavior Checklist), everyday executive functions (Behavior Rating Inventory of Executive Function) and QOL (Child Health Questionnaire) assessed at 6 months post-TBI. RESULTS AND CONCLUSIONS: Severity by time interactions were identified across a range of outcome domains demonstrating that more severe injury is associated with a decrease in functional ability at 6 months post-TBI. This effect was most pronounced for everyday executive skills, social function and internalizing aspects of child behavior. Preinjury function was a consistent predictor of postinjury status. Injury severity contributed little to the prediction of functional outcomes once preinjury functioning was accounted for in the model. Age at injury and family cohesion were relevant to specific outcome domains only. Socio-economic status did not contribute significantly to outcome at 6 months. Preinjury functioning as reported by parents in the acute phase may be a useful predictive tool for identifying children who may be at risk of functioning difficulties 6 months post-TBI.

Early attention impairment and recovery profiles after childhood traumatic brain injury.

OBJECTIVES: To examine recovery of attention from 3 to 6 months postinjury; to identify effects of injury severity and time since injury on performance; to explore whether complex attention skills (eg, shifting, divided attention, attentional control) are more vulnerable to traumatic brain injury (TBI), and slower to recover than simple attention skills (eg, attentional capacity, selective attention, sustained attention). DESIGN: Prospective longitudinal investigation. PARTICIPANTS: A total of 205 school-aged children with TBI were divided into groups according to injury severity (mild = 63%, moderate = 27%, severe = 10%). SETTING: Emergency departments of 3 metropolitan children's hospitals across Australia. MAIN MEASURES: Standardized clinical measures of both simple and complex attention were administered at 3 months and 6 months postinjury. RESULTS: Attention skills were vulnerable to the impact of TBI. More severe injury affected attention skills most negatively. Significant recovery was observed over time. There were few interaction effects, with severity groups exhibiting similar levels of recovery over the 6 months post-TBI. No differences in recovery trajectories were detected for simple and complex attention. CONCLUSIONS: These findings have important clinical and educational implications, suggesting that children with TBI, and particularly those with more serious injuries, are most vulnerable to attention deficits in the acute stages postinjury. It is important that schools and families are aware of these limitations and structure expectations accordingly. For example, gradual return to school should be considered, and in the early stages of recovery, children should be provided with sufficient rest time, with reduced expectations for tasks such as homework.

Acute hepatitis E infection accounts for some cases of suspected drug-induced liver injury.

BACKGROUND & AIMS: The diagnosis of drug-induced liver injury relies on exclusion of other causes, including viral hepatitis A, B, and C. Hepatitis E virus (HEV) infection has been proposed as another cause of suspected drug-induced liver disease. We assessed the frequency of HEV infection among patients with drug-induced liver injury in the United States. METHODS: The Drug-Induced Liver Injury Network (DILIN) is a prospective study of patients with suspected drug-induced liver injury; clinical information and biological samples are collected to investigate pathogenesis and disease progression. We analyzed serum samples, collected from patients enrolled in DILIN, for immunoglobulin (Ig) G and IgM against HEV; selected samples were tested for HEV RNA. RESULTS: Among 318 patients with suspected drug-induced liver injury, 50 (16%) tested positive for anti-HEV IgG and 9 (3%) for anti-HEV IgM. The samples that contained anti-HEV IgM (collected 2 to 24 weeks after onset of symptoms) included 4 that tested positive for HEV RNA genotype 3. Samples from the 6-month follow-up visit were available from 4 patients; they were negative for anti-HEV IgM, but levels of anti-HEV IgG increased with time. Patients who had anti-HEV IgM were mostly older men (89%; mean age, 67 years), and 2 were human immunodeficiency virus positive. Clinical reassessment of the 9 patients with anti-HEV IgM indicated that acute hepatitis E was the most likely diagnosis for 7 and might be the primary diagnosis for 2. CONCLUSIONS: HEV infection contributes to a small but important proportion of cases of acute liver injury that are suspected to be drug induced. Serologic testing for HEV infection should be performed, particularly if clinical features are compatible with acute viral hepatitis.

Keratin variants predispose to acute liver failure and adverse outcome: race and ethnic associations.

BACKGROUND & AIMS: Keratins 8 and 18 (K8/K18) provide anti-apoptotic functions upon liver injury. The cytoprotective function of keratins explains the overrepresentation of K8/K18 variants in patients with cirrhosis. However, K8/K18 variant-associated susceptibility to acute liver injury, which is well-described in animal models, has not been studied in humans. METHODS: We analyzed the entire coding regions of KRT8 and KRT18 genes (15 total exons and their exon-intron boundaries) to determine the frequency of K8/K18 variants in 344 acute liver failure (ALF) patients (49% acetaminophen-related) and 2 control groups (African-American [n = 245] and previously analyzed white [n = 727] subjects). RESULTS: Forty-five ALF patients had significant amino-acid-altering K8/K18 variants, including 23 with K8 R341H and 11 with K8 G434S. K8 variants were significantly more common (total of 42 patients) than K18 variants (3 patients) (P < .001). We found increased frequency of variants in white ALF patients (9.1%) versus controls (3.7%) (P = .01). K8 R341H was more common in white (P = .01) and G434S was more common in African-American (P = .02) ALF patients versus controls. White patients with K8/K18 variants were less likely to survive ALF without transplantation (P = .02). K8 A333A and G434S variants associated exclusively with African Americans (23% combined frequency in African American but none in white controls; P < .0001), while overall, K18 variants were more common in non-white liver-disease subjects compared to whites (2.8% vs 0.6%, respectively; P = .008). CONCLUSIONS: KRT8 and KRT18 are important susceptibility genes for ALF development. Presence of K8/K18 variants predisposes to adverse ALF outcome, and some variants segregate with unique ethnic and race backgrounds.

Hepatotoxicity due to hydroxycut: a case series.

OBJECTIVES: Muscletech Hydroxycut (Iovate Health Sciences Research, Oakville, Ontario, Canada) was a popular weight-loss supplement that was recalled by the manufacturer in May 2009 on the basis of reports of hepatotoxicity associated with this supplement. We sought to characterize the clinical presentation of Hydroxycut-associated liver injury and to adjudicate these cases for causal association with Hydroxycut. METHODS: We assessed the causality and grading of severity of liver injury using methodology developed by the Drug-Induced Liver Injury Network (DILIN) study. RESULTS: Eight patients who developed liver injury after taking Hydroxycut treated at different medical centers were identified. All were hospitalized, and three of eight patients required liver transplantation. Nine other cases with adequate clinical information were obtained from the FDA MedWatch database, including one fatal case of acute liver failure. Usual symptoms were jaundice, fatigue, nausea, vomiting, and abdominal pain. Most patients exhibited a hepatocellular pattern of injury. Adjudication for causality revealed eight cases as definite, five highly likely, two probable, and two were considered to be possible. CONCLUSIONS: Hydroxycut has been clearly implicated as a cause for severe liver injury that may lead to acute liver failure and death. Weight-loss supplements represent a class of dietary supplements that should be regarded as capable of causing severe hepatic toxicity when the usual causes of identified liver injury cannot be otherwise elucidated.

Intravenous N-acetylcysteine improves transplant-free survival in early stage non-acetaminophen acute liver failure.

BACKGROUND & AIMS: N-acetylcysteine (NAC), an antidote for acetaminophen poisoning, might benefit patients with non-acetaminophen-related acute liver failure. METHODS: In a prospective, double-blind trial, acute liver failure patients without clinical or historical evidence of acetaminophen overdose were stratified by site and coma grade and assigned randomly to groups that were given NAC or placebo (dextrose) infusion for 72 hours. The primary outcome was overall survival at 3 weeks. Secondary outcomes included transplant-free survival and rate of transplantation. RESULTS: A total of 173 patients received NAC (n = 81) or placebo (n = 92). Overall survival at 3 weeks was 70% for patients given NAC and 66% for patients given placebo (1-sided P = .283). Transplant-free survival was significantly better for NAC patients (40%) than for those given placebo (27%; 1-sided P = .043). The benefits of transplant-free survival were confined to the 114 patients with coma grades I-II who received NAC (52% compared with 30% for placebo; 1-sided P = .010); transplant-free survival for the 59 patients with coma grades III-IV was 9% in those given NAC and 22% in those given placebo (1-sided P = .912). The transplantation rate was lower in the NAC group but was not significantly different between groups (32% vs 45%; P = .093). Intravenous NAC generally was well tolerated; only nausea and vomiting occurred significantly more frequently in the NAC group (14% vs 4%; P = .031). CONCLUSIONS: Intravenous NAC improves transplant-free survival in patients with early stage non-acetaminophen-related acute liver failure. Patients with advanced coma grades do not benefit from NAC and typically require emergency liver transplantation.

Pharmacokinetics of acetaminophen-protein adducts in adults with acetaminophen overdose and acute liver failure.

Acetaminophen (APAP)-induced liver toxicity occurs with formation of APAP-protein adducts. These adducts are formed by hepatic metabolism of APAP to N-acetyl-p-benzoquinone imine, which covalently binds to hepatic proteins as 3-(cystein-S-yl)-APAP adducts. Adducts are released into blood during hepatocyte lysis. We previously showed that adducts could be quantified by high-performance liquid chromatography with electrochemical detection following proteolytic hydrolysis, and that the concentration of adducts in serum of overdose patients correlated with toxicity. The following study examined the pharmacokinetic profile and clinical associations of adducts in 53 adults with acute APAP overdose resulting in acute liver failure. A population pharmacokinetic analysis using nonlinear mixed effects (statistical regression type) models was conducted; individual empiric Bayesian estimates were determined for the elimination rate constant and elimination half-life. Correlations between clinical and laboratory data were examined relative to adduct concentrations using nonparametric statistical approaches. Peak concentrations of APAP-protein adducts correlated with peak aminotransferase concentrations (r = 0.779) in adults with APAP-related acute liver failure. Adducts did not correlate with bilirubin, creatinine, and APAP concentration at admission, international normalized ratio for prothrombin time, or reported APAP dose. After N-acetylcysteine therapy, adducts exhibited first-order disappearance. The mean elimination rate constant and elimination half-life were 0.42 +/- 0.09 days(-1) and 1.72 +/- 0.34 days, respectively, and estimates from the population model were in strong agreement with these data. Adducts were detected in some patient samples 12 days post-ingestion. The persistence and specificity of APAP-protein adducts as correlates of toxicity support their use as specific biomarkers of APAP toxicity in patients with acute liver injury.

Drug-induced liver injury in clinical trials: as rare as hens' teeth.

Severe drug-induced liver injury is a relatively rare but important public health problem. Extrapolating the incidence of this problem from clinical treatment trials is confounded by a number of issues, including the relatively small size of clinical trials, exclusion criteria for study participation, and active surveillance for liver injury. Advances in understanding the pathogenesis of drug-induced liver injury, as well as its prevention and treatment, will likely require the identification and careful characterization of severe cases in the post-marketing, "real-world" setting as part of a concerted, multi-center, well-orchestrated effort. The Drug-Induced Liver Injury Network (DILIN) represents one example of such an effort.

Excellent outcome following down-staging of hepatocellular carcinoma prior to liver transplantation: an intention-to-treat analysis.

UNLABELLED: We previously reported encouraging results of down-staging of hepatocellular carcinoma (HCC) to meet conventional T2 criteria (one lesion 2-5 cm or two to three lesions <3 cm) for orthotopic liver transplantation (OLT) in 30 patients as a test of concept. In this ongoing prospective study, we analyzed longer-term outcome data on HCC down-staging in a larger cohort of 61 patients with tumor stage exceeding T2 criteria who were enrolled between June 2002 and January 2007. Eligibility criteria for down-staging included: (1) one lesion >5 cm and up to 8 cm; (2) two to three lesions with at least one lesion >3 cm and not exceeding 5 cm, with total tumor diameter up to 8 cm; or (3) four to five lesions with none >3 cm, with total tumor diameter up to 8 cm. A minimum observation period of 3 months after down-staging was required before OLT. Tumor down-staging was successful in 43 patients (70.5%). Thirty-five patients (57.4%) had received OLT, including two who had undergone live-donor liver transplantation. Treatment failure was observed in 18 patients (29.5%), primarily due to tumor progression. In the explant of 35 patients who underwent OLT, 13 had complete tumor necrosis, 17 met T2 criteria, and five exceeded T2 criteria. The Kaplan-Meier intention-to-treat survival at 1 and 4 years after down-staging were 87.5% and 69.3%, respectively. The 1-year and 4-year posttransplantation survival rates were 96.2% and 92.1%, respectively. No patient had HCC recurrence after a median posttransplantation follow-up of 25 months. The only factor predicting treatment failure was pretreatment alpha-fetoprotein >1,000 ng/mL. CONCLUSION: Successful down-staging of HCC can be achieved in the majority of carefully selected patients and is associated with excellent posttransplantation outcome.

Detection of acetaminophen protein adducts in children with acute liver failure of indeterminate cause.

OBJECTIVE: Acetaminophen cysteine protein adducts are a widely recognized correlate of acetaminophen-mediated hepatic injury in laboratory animals. The objective of this study was to use a new assay for the detection of acetaminophen cysteine protein adducts in children with acute liver failure to determine the role of acetaminophen toxicity in acute liver failure of unknown cause. METHODS: Serum samples from children with acute liver failure were measured for acetaminophen cysteine protein adducts using high-performance liquid chromatography with electrochemical detection. For comparison, samples from children with well-characterized acetaminophen toxicity and children with known other causes of acute liver failure also were measured for acetaminophen cysteine protein adducts. The analytical laboratory was blinded to patient diagnoses. RESULTS: Acetaminophen cysteine protein adduct was detected in 90% of samples from children with acute liver failure that was attributed to acetaminophen toxicity, 12.5% of samples from children with acute liver failure of indeterminate cause, and 9.6% of samples from children with acute liver failure that was attributed to other causes. Adduct-positive patients from the indeterminate cause subgroup had higher levels of serum aspartate aminotransferase and alanine aminotransferase and lower levels of bilirubin. Adduct-positive patients also had lower rates of transplantation and higher rates of spontaneous remission. CONCLUSIONS: A small but significant percentage of children with acute liver failure of indeterminate cause tested positive for acetaminophen cysteine protein adducts, strongly suggesting acetaminophen toxicity as the cause of acute liver failure. An assay for the detection of acetaminophen cysteine protein adducts can aid the diagnosis of acetaminophen-related liver injury in children.

Measurement of serum acetaminophen-protein adducts in patients with acute liver failure.

BACKGROUND & AIMS: Acetaminophen toxicity is the most common cause of acute liver failure (ALF) in the United States and Great Britain, but may be underrecognized in certain settings. Acetaminophen-protein adducts are specific biomarkers of drug-related toxicity in animal models and can be measured in tissue or blood samples. Measurement of serum adducts might improve diagnostic accuracy in acute liver failure (ALF) patients. METHODS: We measured serum acetaminophen-protein adducts using high-pressure liquid chromatography with electrochemical detection in coded sera of 66 patients with ALF collected prospectively at 24 US tertiary referral centers. Samples were included from 20 patients with well-characterized acetaminophen-related acute liver failure, 10 patients with ALF owing to other well-defined causes, 36 patients with ALF of indeterminate etiology, and 15 additional patients without ALF but with known acetaminophen overdose and minimal or no biochemical liver injury. RESULTS: Acetaminophen-protein adducts were detected in serum in 100% of known acetaminophen ALF patients and in none of the ALF patients with other defined causes, yielding a sensitivity and specificity of 100%. In daily serial samples, serum adducts decreased in parallel with aminotransferase levels. Seven of 36 (19%) indeterminate cases demonstrated adducts in serum suggesting that acetaminophen toxicity caused or contributed to ALF in these patients. Low adduct levels were present in 2 of 15 patients with acetaminophen overdose without significant liver injury. CONCLUSIONS: Measurement of serum acetaminophen-protein adducts reliably identified acetaminophen toxicity, and may be a useful diagnostic test for cases lacking historical data or other clinical information.