WBR0452

Author	[[PageAuthor::Rim Halaby, M.D. [1]]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Pharmacology
Sub Category	SubCategory::Gastrointestinal
Prompt	[[Prompt::A 24 year old male patient presents to the physician’s office with watery diarrhea of several days 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 wishes to prescribe infliximab. Which of the following tests must be performed before the initiation of infliximab therapy?]]
Answer A	AnswerA::CD4 count
Answer A Explanation	AnswerAExp::CD4 count is important for HIV patients. It is however not pertinent before 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 needed before 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 needed before initiation of anti-TNF therapy.
Answer D	AnswerD::Monospot test
Answer D Explanation	[[AnswerDExp::Monospot test is a helpful test for Epstein-Barr virus (EBV). However, monospot test is not specific and can be positive in other infections and in hematologic malignancies as well. EBV screening is not needed before initiation of anti-TNF therapy.]]
Answer E	AnswerE::Mendel-Mantoux test (PPD test)
Answer E Explanation	[[AnswerEExp::PPD test or Mendel-Mantoux test is helpful in the diagnosis of latent tuberculosis in a healthy individual. However, PPD test can also be positive in individuals who have received the Bacillus Calmette-Guerin (BCG) vaccine. Screening for tuberculosis is necessary before initiation of anti-TNF therapy.]]
Right Answer	RightAnswer::E
Explanation	[[Explanation::Infliximab is a anti-tumor necrosis factor (TNF) monoclonal antibody that inhibits its activity. Infliximab and other TNF inhibitors are effective for treatment of Crohn’s disease. A potential adverse event of anti-TNF use is the reactivation of latent tuberculosis. Hence, PPD test before the initiation of anti-TNF therapy is necessary. TNF, expressed by macrophages and T cells, is integral for the development of granulomas that can limit the reactivation of tuberculosis in immunocompetent patients. Patients who are on anti-TNF therapy will lose the ability to form granulomas, leading to tuberculous reactivation. PPD test or Mendel-Mantoux test is a helpful test in diagnosing latent tuberculosis in individuals who have no signs of active infection. PPD positivity, however, can also be seen in patients who have received Bacillus Calmette-Guerin (BCG) vaccine. Educational Objective: PPD test or Mendel-Mantoux test is helpful in the diagnosis of latent tuberculosis in individuals who have no signs of active infection. Screening for tuberculosis is necessary before initiation of anti-TNF therapy. References: First Aid 2015 page 446]]
Approved	Approved::Yes
Keyword	WBRKeyword::Tuberculosis, WBRKeyword::PPD, WBRKeyword::Mendel-mantoux, WBRKeyword::Infiximab, WBRKeyword::Crohn disease, WBRKeyword::Granuloma, WBRKeyword::Crohn's disease, WBRKeyword::TNF, WBRKeyword::TNF-alpha
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