Causality assessment in drug-induced liver injury using a structured expert opinion process: comparison to the Roussel-Uclaf causality assessment method

Case definition and phenotype standardization in drug-induced liver injury

Drug-induced liver injury (DILI) is the most frequent reason cited for the withdrawal of approved drugs from the market and accounts for up to 15% of the cases of acute liver failure. Investigators around the globe have begun to identify and study patients with DILI; several large registries and tissue banks are being established. In order to gain the maximum scientific benefit from these efforts, the definitions and terminology related to the clinical phenotypes of DILI must be harmonized. For this purpose, an international DILI Expert Working Group of clinicians and scientists reviewed current DILI terminology and diagnostic criteria so as to develop more uniform criteria that would define and characterize the spectrum of clinical syndromes that constitute DILI. Consensus was established with respect to the threshold criteria for definition of a case as being DILI, the pattern of liver injury, causality assessment, severity, and chronicity. Consensus was also reached on approaches to characterizing DILI in the setting of chronic liver diseases, including autoimmune hepatitis (AIH).

Comparability of probable and definite autoimmune hepatitis by international diagnostic scoring criteria

BACKGROUND & AIMS

The diagnostic scoring systems for autoimmune hepatitis categorize some patients as having probable disease; this designation can affect treatment strategies and recruitment to clinical studies. A retrospective study was performed to determine the bases for the classification of probable autoimmune hepatitis and its clinical importance.

METHODS

The study included 185 adult patients who had been assessed at presentation for findings common to both international diagnostic scoring systems.

RESULTS

Seventeen patients (9%) were graded as probable autoimmune hepatitis by the revised original scoring system, and 28 patients (15%) were similarly designated by the simplified scoring system. These patients were distinguished from those designated as definite autoimmune hepatitis by male sex, concurrent immune diseases, lower serum γ-globulin and immunoglobulin G levels, and lower titers of autoantibody. Patients with definite or probable designations by either scoring system responded similarly to conventional corticosteroid regimens during comparable intervals of treatment. Full, partial, or nonresponses and treatment dependence were evident in all diagnostic categories with similar frequencies. Twenty-seven patients designated as probable autoimmune hepatitis by one system were designated as definite autoimmune hepatitis by the other system.

CONCLUSIONS

The designation of probable autoimmune hepatitis by the international scoring systems is based on differences in clinical manifestations and does not reflect differences in the validity of the diagnosis or its treatment response. Large multicenter prospective studies are necessary to establish these observations.

Idiosyncratic drug-induced liver injury: a clinical update

Drug-induced liver injury (DILI) is a rare but potentially devastating adverse drug reaction. Its presentation can range from asymptomatic elevation in liver biochemistries to fulminant liver failure. Over the past decade, clinical and research interest in the field of idiosyncratic DILI has been intense, and several new findings have been reported. In this article, we provide an update on implicated agents, clinical features, outcomes, and the results of recently reported genetic studies.

Drug-induced liver injury: a summary of recent advances

INTRODUCTION

The knowledge base of drug-induced liver injury (DILI) continues to grow each year as additional drugs are identified as hepatotoxins. There is still a need to improve our ability to predict and diagnose DILI in the preclinical and post-approval settings.

AREAS COVERED

This article presents the new and updated DILI registries for 2010, including the latest information on the causes and outcomes of non-acetaminophen DILI cases in the US Acute Liver Failure Study Group database. As DILI is still largely a diagnosis of exclusion, it is appropriate that causality assessment instruments are again the subject of considerable discussion.

EXPERT OPINION

DILI research remains extremely active including studies aimed at being better able to identify causative agents, utilize potential biomarkers, predict who is at greatest risk of injury and manage outcomes. With respect to identifying DILI risk factors at the genetic level, the field is rapidly approaching the day where 'personalized medicine' (based on pharmacogenomics) will become a reality. A large single-center series from India reminds us that geography can influence the drugs responsible for liver injury; however, Hy's law remains universal. As our DILI knowledge continues to grow, it remains essential to keep abreast of the important changes reported each year.

Drug-induced cholestasis

Recent progress in understanding the molecular mechanisms of bile formation and cholestasis have led to new insights into the pathogenesis of drug-induced cholestasis. This review summarizes their variable clinical presentations, examines the role of transport proteins in hepatic drug clearance and toxicity, and addresses the increasing importance of genetic determinants, as well as practical aspects of diagnosis and management.

Drug-induced autoimmune-like hepatitis

The clinical phenotype of classical autoimmune hepatitis can be mimicked by idiosyncratic drug-induced liver injury, and differentiation can be difficult. The goals of this review are to enumerate the major agents of drug-induced autoimmune-like hepatitis, describe the clinical findings and risk factors associated with it, detail the clinical tools by which to assess causality, discuss putative pathogenic mechanisms, and describe treatment and outcome. The frequency of drug-induced autoimmune-like hepatitis among patients with classical features of autoimmune hepatitis is 9%. Minocycline and nitrofurantoin are implicated in 90% of cases. Female predominance, acute onset, and absence of cirrhosis at presentation are important clinical manifestations. Genetic factors affecting phase I and phase II transformations of the drug, polymorphisms that protect against cellular oxidative stress, and human leukocyte antigens that modulate the immune response may be important pathogenic components. Clinical judgment is the mainstay of diagnosis as structured diagnostic methods for drug-induced liver injury are imperfect. The covalent binding of a reactive drug metabolite to a hepatocyte surface protein (commonly a phase I or phase II enzyme), formation of a neoantigen, activation of CD8 T lymphocytes with nonselective antigen receptors, and deficient immune regulatory mechanisms are the main bases for a transient loss of self-tolerance. Discontinuation of the offending drug is the essential treatment. Spontaneous improvement usually ensues within 1 month. Corticosteroid therapy is warranted for symptomatic severe disease, and it is almost invariably effective. Relapse after corticosteroid withdrawal probably does not occur, and its absence distinguishes drug-induced disease from classical autoimmune hepatitis.

Therapeutic acetaminophen is not associated with liver injury in children: a systematic review

BACKGROUND

Concern exists about the potential for liver injury with therapeutic dosing of acetaminophen in children.

OBJECTIVE

We systematically reviewed the medical literature to determine the rate at which liver injury has been reported for children prescribed therapeutic doses of acetaminophen (≤75 mg/kg per day orally or intravenously or ≤100 mg/kg per day rectally).

METHODS

We searched Medline, Embase, and the Cochrane Central Register of Controlled Trials to locate all studies in which acetaminophen was administered to a defined pediatric population for ≥24 hours and for all case reports of liver injury after therapeutic acetaminophen dosing. Trained reviewers extracted data from each report. Major and minor hepatic adverse events (AEs) were defined prospectively. Causality was assessed by using the Naranjo algorithm.

RESULTS

A total of 62 studies that enrolled 32,414 children were included. No child (0% [95% confidence interval: 0.000-0.009]) was reported to have exhibited signs or symptoms of liver disease, to have received an antidote or transplantation, or to have died. Major or minor hepatic AEs were reported for 10 children (0.031% [95% confidence interval: 0.015-0.057]). The highest transaminase value reported was 600 IU/L. Naranjo scores (2-3) suggested "possible" causation. Twenty-two case reports were identified. In 9 cases, the Naranjo score suggested "probable" causation (5-6).

CONCLUSIONS

Hepatoxicity after therapeutic dosing of acetaminophen in children is rarely reported in defined-population studies. Case reports suggest that this phenomenon may occur, but few reports contain sufficient data to support a probable causal relationship.

Causality assessment of herb-induced liver injury using multidisciplinary approach and Roussel Uclaf Causality Assessment Method (RUCAM)

OBJECTIVE

To evaluate an algorithmic approach involving a multidisciplinary team for causality assessment of suspected herb-induced liver injury (HILI) cases and to compare the causality score using this multidisciplinary approach and Roussel Uclaf Causality Assessment Method (RUCAM).

METHODS

A team consisting of hepatologist, clinical toxicologist, analytical toxicologist, and Chinese medicine (CM) pharmacist was formed to do causality assessment based on a protocol for suspected HILI cases. The likelihood of the diagnosis of individual case was first assessed systematically by a hepatologist and clinical toxicologist independently after collecting information about four aspects: (1) clinical course, (2) exclusion of alternative causes, (3) quality of the prescription and herbal product by examining the CM prescriptions and analysis of biological and herb samples, (4) scientific support on comprehensive literature review on English and Chinese medical database, and subsequently concluded in a consensus meeting held by the multidisciplinary team. The final causality score of each patient was compared with the likelihood of causality as assessed by RUCAM.

RESULTS

Between 2005 and 2007, 48 consecutive patients with suspected HILI were enrolled and 21 patients were excluded due to the establishment of an alternative cause of liver impairment or the lack of any information on the herbs taken. Twenty-seven patients were recruited, among them 15 consumed Chinese herbal medicines, 10 used proprietary Chinese medicinal products, and 2 used both. The concordance between the causality assessment of the hepatologist and clinical toxicologist was moderate (weighted κ = 0.48, 95%CI 0.30-0.66). The causality assessment process concluded that the likelihood of HILI was "highly probable" in 5 cases and "probable" in 12, whereas there were 5 "highly probable" and 16 "probable" cases as assessed by RUCAM. The causality assessment by the multidisciplinary approach and RUCAM also showed moderate agreement (weighted κ= 0.51, 95%CI 0.22-0.81).

CONCLUSION

A multidisciplinary approach using defined algorithms is a scientific approach in causality assessment for HILI. Further study is needed to assess its accuracy and applicability.

Duloxetine hepatotoxicity: a case-series from the drug-induced liver injury network

BACKGROUND

Case reports suggest that duloxetine hepatotoxicity may arise, but risk factors, presenting features and clinical course are not well-described.

AIM

To describe the presenting features and outcomes of seven well-characterized patients with suspected duloxetine hepatotoxicity.

METHODS

Patients enrolled in the Drug-Induced Liver Injury Network Prospective Study underwent an extensive laboratory and clinical evaluation to exclude competing aetiologies of liver injury as well as a standardized assessment for causality and disease severity.

RESULTS

Between 1/2006 and 9/2009, six of the seven cases of DILI attributed to duloxetine were assessed as definite or very likely. Median patient age was 49 years, six (86%) were women and the median latency from drug initiation to DILI onset was 50 days. Six patients developed jaundice and the median peak alanine aminotransferase in the five patients with acute hepatocellular injury was 1633 IU/L. Ascites developed in one patient and acute renal dysfunction in two others (29%). All patients recovered without liver transplantation even though three had pre-existing chronic liver disease. Liver histology in four cases demonstrated varying patterns of liver injury.

CONCLUSIONS

Duloxetine hepatotoxicity developed within 2 months of drug intake and led to clinically significant liver injury. A spectrum of laboratory, histological and extra-hepatic features were noted at presentation.

Regulatory causality evaluation methods applied in kava hepatotoxicity: are they appropriate?

Since 1998 liver injury has been assumed in some patients after the use of kava (Piper methysticum G. Forster) as an anxyolytic herbal extract, but the regulatory causality evaluation of these cases was a matter of international and scientific debate. This review critically analyzes the regulatory issues of causality assessments of patients with primarily suspected kava hepatotoxicity and suggests recommendations for minimizing regulatory risks when assessing causality in these and other related cases. The various regulatory causality approaches were based on liver unspecific assessments such as ad hoc evaluations, the WHO scale using the definitions of the WHO Collaborating Centre for International Drug Monitoring, and the Naranjo scale. Due to their liver unspecificity, however, these causality approaches are not suitable for assessing cases of primarily assumed liver related adverse reactions by drugs and herbs including kava. Major problems emerged trough the combination of regulatory inappropriate causality assessment methods with the poor data quality as presented by the regulatory agency when reassessment was done and the resulting data were heavily criticized worldwide within the scientific community. Conversely, causality of cases with primarily assumed kava hepatotoxicity is best assessed by structured, quantitative and liver specific causality algorithms such as the scale of the CIOMS (Council for International Organizations of Medical Sciences) or the main-test as its update. Future strategies should therefore focus on the implementation of structured, quantitative and liver specific causality assessment methods as regulatory standards to improve regulatory causality assessments for liver injury by drugs and herbs including kava.

Standardization of nomenclature and causality assessment in drug-induced liver injury: summary of a clinical research workshop

Idiosyncratic drug-induced liver injury (DILI) is an important but relatively infrequent cause of potentially severe acute and chronic liver injury. The aim of this clinical research workshop was to review and attempt to standardize the current nomenclature and terminology used in DILI research. Because DILI is a diagnosis of exclusion, selected elements of the medical history, laboratory tests, and previous reports were proposed to improve causality assessment. Definitions and diagnostic criteria regarding the onset of DILI, evolution of liver injury, risk factors, and mandatory testing versus optional testing for competing causes were reviewed. In addition, the role of intentional and inadvertent rechallenge, liver histology, and host genetic polymorphisms in establishing the diagnosis and prognosis of DILI were reviewed. Consensus was established regarding the need to develop a web-of-knowledge database that provides concise, reliable, and updated information on cases of liver injury due to drugs and herbal and dietary supplements. In addition, the need to develop drug-specific computerized causality assessment methods that are derived from prospectively phenotyped cases was a high priority. Proposed scales for grading DILI severity and assessing the likelihood of an agent causing DILI and written criteria for improving the reliability, accuracy, and reproducibility of expert opinion were reviewed. Finally, the unique challenges of assessing causality in children, patients with underlying liver disease, and subjects taking herbal and dietary supplements were discussed.

CONCLUSION

Workshop participants concluded that multicenter referral networks enrolling patients with suspected DILI according to standardized methodologies are needed. These networks should also collect biological samples that may provide crucial insights into the mechanism(s) of DILI with the ultimate aim of preventing future cases of DILI.