Doctor insights on:
Ppd Skin Testing
Nothing is perfect: No test is 100% reliable - neither skin testing nor blood testing. That's why allergists try to order relevant tests selected based on a comprehensive medical history and physical examination. The results must be interpreted & used as clues to a solution. They're not an answer in themselves. I'm frequently called by doctors who order allergy tests & then want me interpret them over the phone. ...Read moreSee 2 more doctor answers
Does desensitization vaccination works for allergic asthma?I got positive skin prick tests for 4-5 allergens....
Yes: It is effective about 80% of the time. However I'd doubt that getting allergy shots for 4-5 allergens would work for you since most people are allergic to dozens of airborne allergens except in the case of occupational exposure. ...Read more
Tb skin test negative, quentform TB test negative, bone marrow biopsy results indicative of TB (reacts to ziehl niehlssen), PCR negative. How come?
No...actually: The zn stain is a broad stain for acid fast bacilli of which mycobacterium tuberculosis is one of many. The specific tests like quantiferon or the pcr test are against you having tb. The culture is the "gold standard" but you will need to wait for it. It might turn out be a cousin of TB and that too will grow out of culture. Stay on TB meds until they are certain of the AFB positive organism. ...Read more
Yes, helpful: I agree. Skin prick testing to evaluate for food allergies can be very helpful, and can help direct dietary restriction. It is always used in clinical context to support an adverse reaction to a food. The size of the reaction will indicate the likelihood of an adverse reaction and not if you will have anaphylaxis. ...Read moreSee 1 more doctor answer
Is an IGE allergy blood test as accurate as a skin test? My skin test from 1 year prior to IGE blood test showed additional allergens.
Likely complementary: Although prick skin test is considered better in detecting food allergies the results of blood tests are complementary. I often order the blood test first in a case of a food suspected of causing anaphylaxis. If the result is negative or equivocal, then I would proceed with a skin test prior to a food challenge. The results are at times discrepant. ...Read more
Limited use: Skin testing for allergy is of limited usefulness even when a person does not have dermatographism. The history is the key; skin testing can be confirmatory. Especially, don't conclude that you must severely limit what you do and eat, and where you go, based on skin testing. It's just one piece of information that helps guide decisions. ...Read more
Yes: Yes, this is a good way to assess if one has significant food allergies, as well as air- born allergies. ...Read more
Quickly & accurately: Allergy skin testing is the preferred method to assess for allergies. A drop of allergen extract (such as pollen, dust mite, dander, mold, food, etc) is place on the plastic skin test device and applied to the skin. Mast cells in the skin that have attached IgE (allergic antibody) will degranulate leading to a wheal/flare reaction (small hive) at the site of the test if positive in 20 minutes. ...Read more
How do doctors differentiate between a positive TB skin test due to BCG vaccine vs latent TB infection?
Blood test: There is a blood test which can help tell the difference. ...Read more
Tuberculosis: Ppd (purified protein derivative) is a test for exposure to tuberculosis. If you have a postive test, you have been exposed and your body is making antibodies. If your exposure was through a vaccine (called bcg) treatment might not be necassary. More likely, a chest xray will be ordered. If that shows evidence of disease, then several drugs will be given over several months to cure it. ...Read more
2 TB skin tests. Bumps measured 15cm. RN stated I possibly have LTBI & ordered QuantiFERON Gold in-tube test. Could anything cause a false positive?
Not at 15cm, but...: The bump is more likely 15mm, because 15cm is 6 inches and HUGE. A 15mm bump on a screening test is big but may still be a false positive (a screening test means the patient has NO symptoms of tuberculosis). If a patient has contacted somebody with TB, or has current symptoms, she likely has a true positive unless her bump is due to past BCG vaccine. The Quantiferon-TB blood test is very accurate ...Read moreSee 1 more doctor answer
No: Fortunately not or we would not be able to perform this test on more than one occasion. ...Read more
Is it possible to have an HIV p24 antigen, HIV antibody, and HIV PCR accurate 5 weeks after exposure?
Yes in part: The tests that detect actual HIV virus, such a the HIV viral load (pcr), will likely be positive 5 weeks after an exposure that results in transmission of hiv. The HIV antibody test may still be undetectable. So, if you are very worried about acute hiv, it is very important to discuss with your health provider so they do the right tests. ...Read more
Tuberculosis vaccinated, TB test positive...Will my ANA be positive because of TB test positive due to vaccine?
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