Clinical Roundtable Monograph: Risk of Biologic Therapy–Associated Progressive Multifocal Leukoencephalopathy: Use of the JC Virus Antibody Assay in the Treatment of Moderate-to-Severe Crohn’s Disease

Gary R. Lichtenstein, MD, Stephen B. Hanauer, MD, and William J. Sandborn, MD

Abstract: For treatment of moderate-to-severe active Crohn’s disease, clinicians generally rely on immunosuppressants (including azathioprine and 6-mercaptopurine), corticosteroids, and antibodies against tumor necrosis factor α. However, a significant proportion of patients do not respond to these therapies, lose response over time, or are intolerant to these therapies. In such cases, one of the only remaining pharmacologic treatment options is natalizumab, an α4 integrin–targeted antibody. Unfortunately, 3 cases of progressive multifocal leukoencephalopathy (PML) were reported in natalizumab-treated patients in 2005, shortly after natalizumab’s approval by the US Food and Drug Administration (FDA). Natalizumab was subsequently withdrawn from the market but was then reintroduced in 2006 under close supervision by the FDA. Careful review of postmarketing data revealed 3 major risk factors for the development of natalizumab-associated PML, the most significant of which is prior exposure to the JC virus (JCV). To help identify patients who may be at higher risk for developing natalizumab-associated PML, a JCV antibody assay was developed that can detect anti-JCV antibodies in patients’ blood. Clinicians can now consider a patient’s anti-JCV antibody status together with the other major risk factors for natalizumab-associated PML—duration of natalizumab therapy and prior immunosuppressant use—to more accurately gauge the risks and benefits of natalizumab therapy in a particular patient.

Clinical Roundtable Monograph: Contemporary Diagnostic Strategies for the Detection of Helicobacter pylori Infection

Adam B. Elfant, MD, FACG, Colin W. Howden, MD, and Neil Stollman, MD, FACP, FACG, AGAF

Helicobacter pylori infection is highly prevalent, affecting approximately half of the world’s population. While the majority of infected individuals are asymptomatic, H. pylori infection is associated with certain diseases, including peptic ulcers (either duodenal or gastric), gastritis, and 2 malignancies—gastric cancer and gastric mucosa–associated lymphoid tissue lymphoma. Many of the epidemiologic associations between these diseases and H. pylori infection have been further validated by treatment studies, which show that effective eradication therapy correlates with a decreased risk of disease. A variety of testing strategies are used to detect H. pylori infection. Serologic techniques are widely available and inexpensive, but they are no longer preferred as they have low sensitivities and specificities, and they may show a positive result for a long period following effective therapy. The remaining testing methods are divided into 2 categories: invasive tests (which require endoscopy) and noninvasive tests. Noninvasive test methods such as the urea breath test and stool antigen test have gained popularity due to their high sensitivities and specificities. Further, both of these methods may be used to confirm the absence of infection following eradication therapy. Due to the increasing incidence of treatment failure (caused in part by antibiotic resistance), post-treatment testing is recommended to confirm H. pylori eradication.

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