WBR0452
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| 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. |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Tuberculosis, WBRKeyword::PPD, WBRKeyword::Infiximab, WBRKeyword::Crohn disease, WBRKeyword::Granuloma, WBRKeyword::Crohn's disease, WBRKeyword::TNF, WBRKeyword::TNF-alpha |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |