yunuz
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A laboratory worker has been diagnosed as having TB.He has been ill for 4 months with symptoms that include a productive couch, intermittant fever, night seats, weight loss.Numerous acid-fast bacilli are seen in a sputum examination, and more than 50 colonies grow out in culture.
In this situation, those contacts who have (+) skin test but no other signs should:
a- Receive prohylaxis w/INH
b-Receive a full course of etnambutol
c-Be checked periodically by Xray.
d-Be immuninized with BCG
e-Be checked periodically by sputum culture
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| new_n_lost
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e-Be checked periodically by sputum culture
Previous Immunization to BCG results also in a positive skin test. But the definitive diagnosis lies with Sputum culture.
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| silver
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e-Be checked periodically by sputum culture
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| drgho
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A.
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| yunuz
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The correct Answer is (A).
Exposure to to the TB bacillus does not assure disease, but a (+) skin test makes the diagnosis more likely.Chemoprolhylaxis with INH would be the Rx of choice for contacts of actively infected persons.Ethambutol is very effecive against most mycobacteria but would be used in the Rx in the therapy against TB, not in prophylaxis.The skin test is the most sensitive index of infection, and for individuals who have already shown a + response, X rays would not add much information.Immunisation with live attenuated vaccine BCG would be pointless, as the contacts have already experienced an infection with M.tuberculosis.Individuals RECIVING INH should be periodically be checked by sputum culture and X ray to assure that the therapy is effective.
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| new_n_lost
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Can u tell me where is this question from i.e source of the question cos i did a similar question in UW and the answer given was repeat sputum culture. 
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| silver
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as far as i know the skin test done in TB has a margin of false positive, therefore, when a person who has no clinical signs of the illness shows up with a +skin test, he/she should be followed up with serial sputum culture test to diagnose and confirm.
a +skin test is not a confirmatory test. it makes more sense to follow up the contacts with sputum culture when they're not showing any signs than to directly put them on prophylactic treatment.
yeah, i'd like to know where this is from too. let us know!!
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| drgho
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I think in this case, the confirmation of diagnosis is not the priority. The skin test + people with active TB contact can already have latent infection. So they should get prophylaxis with INH. The study already showed that in such people the incidence of active TB can be reduced by about 60% by giving INH prophylaxis and no evidence of emergence of INH resistance because of the prophylactic therapy. So, i think prophylaxis is a must do. Yep, followup for diagnosis may be needed. But I think the question really wants to ask what one should do for the possible latent infection rather than how to diagnose an active TB. That is what I think but other explanations may be possible. Actually both prophylaxis and some form of followup is needed.
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| bactitech
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My skin test converted with an 18 mm induration in 1999. It was due to a lab exposure. I won't go into the details - suffice it to say I was NOT the one who screwed up. There were three of us that had our PPD convert to positive. All three of us went on INH. It was considered a cluster exposure.
Let me say that a positive PPD is very painful. In addition to the wheal at the site, my forearm in general swelled up. There are different indurations that are considered positive or negative depending on whether the patient is HIV positive/negative/immunocompromised, etc. It took over a month for my arm to go back to normal. I knew in less than a day that my goose was cooked and it was going to turn positive from the way my arm was reacting. I never EVER want to go through that again. I kept all my papers and documentation. Make sure you do this if it ever happens to you because you do NOT want to go through this twice.
At that point, I insisted on seeing an infectious disease doc of my choice (as the lab would pay for it). I got a chest X-ray, which was negative. She put me on INH for six months, along with Vitamin B6, I believe. I had blood work a couple of times to check my liver enzymes. There were no sequelae, other than that I could not drink alcohol for six months. I don't drink very much, but when you can't AT ALL it's kind of weird.
You cannot fool around with TB. You must give something for prophylaxis. Sputum cultures for people who are not sick and cannot produce sputum are a waste of time, believe me. All you get is saliva. A deep cough can't be produced in someone without respiratory distress. If you don't believe me, try huckering up at least 5 ml of good sputum from a deep cough right now if you don't have a cold. We reject anything less than 5 ml for an acid fast culture. Saliva does NOT count.
A positive PPD means that you have been EXPOSED to the organism. You must take a round of INH regardless of chest xray results. If you become immunocompromised later on the TB can reactivate.
More information on the topic:
http://www.cdc.gov/ncidod/dhqp/id_tb_excerpts.htm...
http://www.cdc.gov/mmwr/preview/mmwrhtml/00031075... - PPD positive/HIV positive
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| yunuz
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Thank bactitech for your detailed explanation.
The Q is taken from Appleton an Lange Review for Usmle, edition 1996.
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| SmokyWaters
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the answer shud be INH prophylaxis for six months..
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| yunuz
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So I guess if they added another option like:
f-Receive a prophylaxis with INH, and be checked periodically by sputum culture.
This (f) would be the best answer, right?
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| drgho
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yunuz wrote:
So I guess if they added another option like:
f-Receive a prophylaxis with INH, and be checked periodically by sputum culture.
This (f) would be the best answer, right?
I think, sputum culture may not be that sensitive one to detect early stage of active TB. In my opinion, followup for clinical symptoms plus some CXR together with serial ESR and complete blood count will be more sensitive to detect early TB activity rather than sputum culture. Sure, even these turn positive, diagnosis is just more likely than not..and won't give definite diagnosis. If there are obvious symptoms, sputum culture and sensitivity should be no.1 test. second, once some antiTB is taken and the organism is sensitive to that antiTB, culture turns negative earlier compared to sputum for AFB. So, the culture will be likely to turn out consecutively negative in this case if they took prophylaxis. and i don't think this combination of INH and sputum C&S is the best option.
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| silver
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bactitech wrote:
A positive PPD means that you have been EXPOSED to the organism.
not neccesarily. what do you do with people who have been vaccinated with BCG?? they're also going to give you a +PPD. so then what? you're going to shove ATT down their throats as well?
someone who walks in to your office with no active symptoms of the illness and just has a +PPD should be further worked up on with at least a chest Xray. fine, i agree, bringing up sputum in someone who is not coughing is difficult, but then at least do a chest Xray or get a history of whether they've been vaccinated or not.
as it is the patient compliance is soo poor for ATT...asking someone to take these meds who has no active symptoms and feels healthy---he/she will never agree.
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