Question of the Week # 246

246 )  A 32 year old Mexican woman is evaluated in your office because she is concerned about her potential exposure to Tuberculosis. Her father has come to visit her from Mexico and he was diagnosed with cavitary tuberculosis of left lung three week ago. He is currently receiving multi-drug anti-tuberculosis therapy. The patient says she has been taking care of her father at home since the diagnosis was made. A Tuberculin skin test is administered and is negative after 72 hours. Patient denies any fever, cough, chest pain or weight loss. Which of the following is most appropriate management ?

A) Re-assurance

B) Repeat PPD in 3 months

C) Start Isoniazid

D) Chest X-ray

E) Repeat PPD in one year

12 Responses

  1. B) Repeat PPD in 3 months is my vote

  2. bbbbbbbbbbb

  3. b

  4. B….Repeat skin test three months after last exposure to infectious case.

  5. bbb

  6. B) Repeat PPD in 3 months

  7. bbbbbbbbbbbbb

  8. we should repeat ppd in 3 mon; meanwhile start isoniazid;if the rpt ppd is negative stop Isoniazid,,if it is positive continue isoniazid till 9 mon.
    correct me if wrong !

  9. c

  10. Postexposure Tuberculin Skin Testing

    Among persons who have been sensitized by M. tuberculosis infection, the intradermal tuberculin from the skin test can result in a delayed-type (cellular) hypersensitivity reaction. Depending on the source of recommendations, the estimated interval between infection and detectable skin test reactivity (referred to as the window period) is 2–12 weeks (6,95). However, reinterpretation of data collected previously indicates that 8 weeks is the outer limit of this window period (46,102–106). Consequently, NTCA and CDC recommend that the window period be decreased to 8–10 weeks after exposure ends. A negative test result obtained <8 weeks after exposure is considered unreliable for excluding infection, and a follow-up test at the end of the window period is therefore recommended.

    Low-priority contacts have had limited exposure to the index patient and a low probability of recent infection; a positive result from a second skin test among these contacts would more likely represent boosting of sensitivity. A single skin test, probably at the end of the window period, is preferred for these contacts. However, diagnostic evaluation of any contact who has TB symptoms should be immediate, regardless of skin test results.

    Nonspecific or remote delayed-type hypersensitivity (DTH) response to tuberculin (PPD in the skin test) occasionally wanes or disappears over time. Subsequent TSTs can restore responsiveness; this is called boosting or the booster phenomenon (95,107). For contacts who receive two skin tests, the booster phenomenon can be misinterpreted as evidence of recent infection. This misinterpretation is more likely to occur for foreign-born contacts than it is for those born in the United States (17,108).

    Skin test conversion refers to a change from a negative to a positive result. To increase the relative certainty that the person has been infected with M. tuberculosis in the interval between tests, the standard U.S. definition for conversion includes a maximum time (2 years) between skin tests and a minimum increase (10 mm) in reaction size (6,34). With the 5 mm cut-off size used for interpreting any single skin test result obtained in contact investigations, the standard definition for conversion typically is irrelevant. For these guidelines, contacts who have a positive result after a previous negative result are said to have had a change in tuberculin status from negative to positive.
    answer B:) repeat the PPD after window period 2-12 weeks.

  11. Start patient on INH therapy for 6 to 9months is the answer.

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