WBR0452

Author	[[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Yazan Daaboul, M.D.)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Pharmacology
Sub Category	SubCategory::Gastrointestinal
Prompt	[[Prompt::A 24-year-old man presents to the physician’s office with watery diarrhea of several weeks duration. Following appropriate work-up, the patient undergoes intestinal biopsy that reveals transmural inflammatory infiltration with granulomatous skip lesions. The patient is then diagnosed with Crohn’s disease. The physician prescribes infliximab and informs the patient of the benefits and risks of infliximab therapy. Which of the following tests must be performed before the initiation of infliximab?]]
Answer A	AnswerA::CD4 count
Answer A Explanation	AnswerAExp::CD4 count is used to follow-up patients with HIV. HIV testing is not required prior to the initiation of anti-TNF therapy.
Answer B	AnswerB::HBsAg
Answer B Explanation	AnswerBExp::HBsAg is diagnostic of hepatitis B virus (HBV). HBV screening is not recommended prior to the initiation of anti-TNF therapy.
Answer C	AnswerC::HCV RNA
Answer C Explanation	AnswerCExp::HCV RNA is diagnostic of hepatitis C virus (HCV). HCV screening is not recommended prior to the initiation of anti-TNF therapy.
Answer D	AnswerD::Monospot test
Answer D Explanation	[[AnswerDExp::Monospot test is a diagnostic test for active Epstein-Barr virus (EBV) infection. Monospot test, however, is not specific and can be positive in other infections and hematological malignancies. EBV screening is not recommended prior to the initiation of anti-TNF therapy.]]
Answer E	AnswerE::PPD test
Answer E Explanation	AnswerEExp::PPD test test is diagnostic of latent tuberculosis. Screening for tuberculosis is recommended prior to the initiation of anti-TNF therapy.
Right Answer	RightAnswer::E
Explanation	[[Explanation::Infliximab is a anti-tumor necrosis factor (TNF) monoclonal antibody. Infliximab and other TNF inhibitors are effective for the treatment of Crohn’s disease. A potential adverse event of anti-TNF therapy is the reactivation of latent tuberculosis. Accordingly, PPD test prior to the initiation of anti-TNF therapy is often recommended. TNF, expressed by macrophages and T cells, is integral for the development of granulomas and can limit the reactivation of tuberculosis in immunocompetent patients. Patients who receive anti-TNF therapy will lose the ability to form granulomas and are at an increased risk of tuberculous reactivation. PPD test is helpful in diagnosing latent tuberculosis among individuals who have no signs of active infection. PPD positivity, however, can also suggest a history of Bacillus Calmette-Guerin (BCG) vaccine within the past 10 years. Educational Objective: PPD test test is diagnostic of latent tuberculosis. Screening for tuberculosis is recommended prior to the initiation of anti-TNF therapy. References: First Aid 2015 page 446.]]
Approved	Approved::Yes
Keyword	WBRKeyword::Tuberculosis, WBRKeyword::PPD, WBRKeyword::Infiximab, WBRKeyword::Crohn disease, WBRKeyword::Granuloma, WBRKeyword::Crohn's disease, WBRKeyword::TNF, WBRKeyword::TNF-alpha
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