WBR0494
| Author | [[PageAuthor::Rim Halaby, M.D. [1], Alison Leibowitz [2] (Reviewed by Alison Leibowitz)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Immunology |
| Sub Category | SubCategory::Endocrine |
| Prompt | [[Prompt::A 27-year-old newly graduated nurse applying for a job at a hospital has to submit a copy of her vaccination history and undergo a PPD test, to screen for tuberculosis. She receives an intradermal injection of PPD and is asked to return 48 hours later, so that site of injection can be reevaluated. Which of the following mechanisms is involved if the female returns with an induration at the site of the PPD injection?]] |
| Answer A | AnswerA::Hypersensitivity type I |
| Answer A Explanation | [[AnswerAExp::Type I hypersensitivity disorders include anaphylaxis, atopy, and allergy. A PPD skin test is not a type I hypersensitivity immune reaction.]] |
| Answer B | AnswerB::Hypersensitivity type II |
| Answer B Explanation | AnswerBExp::Type II hypersensitivity disorders include conditions where an antibody is directed against a specific antigen. A PPD skin test involves a delayed T cell mediated response that is consistent with type IV hypersensitivity. |
| Answer C | AnswerC::Hypersensitivity type III |
| Answer C Explanation | AnswerCExp::Hypersensitivity type III disorders include conditions where an antigen-antibody complex forms and activates the complement system. A PPD skin test is not a type III hypersensitivity immune reaction. |
| Answer D | AnswerD::Hypersensitivity type IV |
| Answer D Explanation | [[AnswerDExp::Hypersensitivity type IV disorders include conditions characterized by delayed T-cell mediated immune reactions, such as contact dermatitis and tuberculosis testing.]] |
| Answer E | AnswerE::Not a hypersensitivity disorder |
| Answer E Explanation | AnswerEExp::PPD skin test is a type IV hypersensitivity disorder. |
| Right Answer | RightAnswer::D |
| Explanation | [[Explanation::PPD test, also known as the Mantoux test, tuberculin sensitivity test, and Pirquet test, is a screening tool for tuberculosis. The individual's medical risk factors determine the increment (5 mm, 10 mm, or 15 mm) of induration at which the result is considered positive. A PPD test, a type IV hypersensitivity immune reaction, is characterized by delayed T-cell mediated immune reactions. Educational Objective: Hypersensitivity type IV disorders include conditions characterized by delayed T-cell mediated immune reactions, such as contact dermatitis and PPD testing. |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Hypersensitivity, WBRKeyword::PPD test, WBRKeyword::immune system, WBRKeyword::testing, WBRKeyword::TB, WBRKeyword::tuberculosis, WBRKeyword::screening |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |