Acute Hepatitis E Infection Accounts for Some Cases of Suspected Drug-Induced Liver Injury

TL;DR: HEV infection contributes to a small but important proportion of cases of acute liver injury that are suspected to be drug induced, andSerologic testing for HEV infection should be performed, particularly if clinical features are compatible with acute viral hepatitis.

About: This article is published in Gastroenterology.The article was published on 2011-11-01 and is currently open access. It has received 295 citations till now. The article focuses on the topics: Hepatitis E & Viral hepatitis.

Summary

Introduction

• Drug-induced liver injury is the leading cause of acute liver failure and the primary reason for regulatory action leading to failed drug approval, market withdrawal, usage restrictions and warnings to practicing physicians in the United States.
• The diagnosis is primarily one of exclusion and is made only after elimination of common causes of liver disease, such as alcoholic hepatitis, metabolic and genetic liver diseases, bile duct obstruction, and hepatitis A, B, and C virus infection (HAV, HBV, and HCV).
• 3 Several recent findings have served to alter this opinion.
• The aims of the current study were to assess whether acute hepatitis E accounts for some cases of suspected drug-induced liver injury in the United States and whether testing for HEV infection is warranted in the routine evaluation of patients with acute liver disease of unknown cause.

Patient identification and causality analysis

• The Drug Induced Liver Injury Network consists of multiple (previously 5, and currently 8) U.S. clinical sites and a data coordinating center that have enrolled patients with suspected drug-induced liver injury into a prospective study since 2004.
• The rationale, design and conduct of the DILIN, as well as a summary of the first 300 enrolled cases have been described.
• 16, 17 All enrolled cases were subjected to formal causality assessment independently by three investigators, and a final causality score was obtained by consensus.
• 18 At the same time, a Roussel Uclaf Causality Assessment score 19 was determined and cases were graded for severity using a five-point scale developed by the DILIN.

Serologic and Virologic Testing

• Serum samples were obtained at the time of enrollment, which might be as long as 6 months after the onset of liver injury, and were stored at -80 degrees Celsius in a central repository.
• For the current study, serum samples from the first 318 patients enrolled were tested for IgM and IgG anti-HEV using enzyme immunoassays of established sensitivity and specificity.
• 20, 21 Samples with IgM anti-HEV and those with strongly positive reactions for IgG anti-HEV were further tested for HEV RNA using nested reverse transcription polymerase chain reaction (RT-PCR) 22 and the PCR products were separated by electrophoresis on ethidium bromide-stained agarose gels, extracted from the gel and directly sequenced to provide the consensus sequence.
• A BLAST search of GenBank nucleotide sequences was performed to determine HEV genotype.
• Details of the ELISA assays for anti-HEV and the PCR for HEV RNA are provided in Supplementary Material.

Histological Analysis

• When available, liver biopsies (n=3) were reviewed by a hepatic pathologist (D.E.K.) who was unaware of the medications implicated and results of HEV testing.
• Histological features of inflammation, fibrosis, steatosis, cholestasis, vascular injury and other findings were systematically recorded, along with a description of the overall pattern of injury.

Repeat Causality Analysis

• Cases positive for HEV IgM were subjected to repeat causality analysis by three independent reviewers after the results of HEV serological and RT-PCR testing were available.
• 18 Cases were also judged using the same scale as to the likelihood that the liver injury was due to acute hepatitis E based upon the clinical, biochemical and histological findings.

Data analysis

• Pairwise comparisons were performed between the cases with no serological evidence of HEV infection versus patients with evidence of active or recent HEV infection (defined by presence of HEV IgM) and those with distant and resolved HEV infection (defined by presence of IgG without IgM anti-HEV).
• The Wilcoxon test was used for continuous variables, Fisher's exact test for binary outcomes, and the Pearson chi-squared test for other categorical variables.

IRB approval

• All details of the DILIN Prospective study were reviewed and approved by the institutional review boards of each clinical site and the data coordinating center.
• In addition, the protocol for anti-HEV testing was specifically approved by the institutional review board of the National Institute of Allergy and Infectious Diseases of the intramural program of the National Institutes of Health.

Serological Testing

• Initial and peak serum bilirubin, alanine aminotransferase (ALT) and alkaline phosphatase levels were similar in the three groups of patients.
• Furthermore, the three groups did not different in distribution of pattern of serum enzyme elevations, severity scores or causality scores.

Demographic and Clinical Features of IgM anti-HEV Positive Cases

• Selective demographic and clinical features of the nine IgM anti-HEV positive cases are given in Table 2 , and detailed case summaries of each patient are provided as Supplementary Data.
• The clinical course was considered severe in three patients who manifested signs of hepatic failure such as elevations in INR > 1.5, ascites or hepatic encephalopathy.
• Information on exposures to farm animals or raw pork was not specifically sought but none offered such information or gave a history of travel to an endemic area.
• The patients were geographically diverse and presented at 4 of the 5 DILIN centers including Indiana (n=5), San Francisco (n=2), Connecticut (n=1) and North Carolina (n=1) between 2004 and 2006.

HEV RNA results

• Four patients with IgM anti-HEV were also reactive for HEV RNA, and all four harbored genotype 3.
• Sequencing analyses showed that the four were not closely related phylogenetically (data not shown) and therefore were not likely due to a single source or contamination, presenting in different geographic areas (Indiana, San Francisco and North Carolina).
• The four cases with viremia included both patients with HIV infection.
• Follow-up serum samples, drawn approximately 6 months after enrollment, were available from four IgM anti-HEV-positive subjects: all had an increase in IgG anti-HEV titer, but IgM anti-HEV had diminished in titer or had become negative, consistent with seroconversion after acute infection.
• All were also negative for HEV RNA (two were positive on the earlier specimen) (Table 3 ).

Causality Analysis/Re-analysis

• The initial causality assessment for the nine cases concluded that 4 were highly likely, 3 probably and 2 possibly due to drug-induced liver injury.
• 21 Thus, most cases were considered compatible with drug-induced liver injury on initial assessment in the absence of anti-HEV results.
• Even with the information on HEV serology, two cases (implicated medications being allopurinol and telithromycin) were still considered probably due to drug-induced liver injury rather than hepatitis E. Both patients presented late during the course of illness and initial clinical features and laboratory results were not available.
• The remaining seven cases were considered more likely to be acute hepatitis E than drug-induced liver injury, although four were still considered "possibly" due to the medication.
• Three cases were considered "definite" acute hepatitis E.

Liver histology of IgM anti-HEV positive cases

• Liver biopsy tissue was available from three patients.
• The bile ducts showed mild injury with reactive changes, but without cholestasis.
• Case 4 developed mild acute liver injury with jaundice after taking ezetimibe for one year and underwent liver biopsy during recovery when serum bilirubin (1.4 mg/dL) and ALT levels (60 U/L) were close to normal.
• The biopsy (not shown) showed mild steatosis, ballooning and bridging fibrosis with focal copper accumulation consistent with nonalcoholic steatohepatitis which he was thought to have before onset of the acute injury (based upon chronic ALT elevations and obesity).
• Case 7 developed jaundice and a hepatitis-like syndrome 1.5 years after starting an antiretroviral regimen including nevirapine and on liver biopsy had changes of lobular disarray, spotty hepatocyte necrosis without confluence, marked lobular but scant portal inflammation, mild intrahepatic cholestasis but no bile duct injury, steatosis or fibrosis.

Discussion

• The accurate diagnosis of drug-induced liver injury is critically important not only for patient care, but also for drug development, as even a single episode of severe liver damage associated with a drug during pre-marketing clinical testing may undermine its subsequent approval and marketing.
• These findings suggest that the recent acute HEV infection detected by IgM anti-HEV testing did not account for the acute liver injury in all cases and that co-incidental, subclinical hepatitis E may have preceded the acute liver injury caused by the implicated medication.
• In the remaining five patients the absence of viremia may have been due to the delay between the onset of symptoms and blood sampling for the study, as patients were typically referred by local physicians to the DILIN investigators days or even weeks after initial presentation.
• The presence of serological evidence of acute hepatitis E should also prompt a search for possible sources of infection, such as foreign travel, exposure to farm animals, consumption of undercooked pork or wild game, and close personal contact with chronically immunosuppressed persons.
• Finally, these findings underscore the need for sensitive and reliable, commercially available assays for HEV infection in the United States and reexamination of the possible benefit of an HEV vaccine.