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Tuberculosis

Negative Reading

10/20/2009

Question:

My child is 2yrs old. He`s going to go get his reading done in two days. How low should his TB reading be in order for it to be a negative reading? Thanks.

Answer:

The interpretation of a TB skin test depends upon the risk factors of the patient who is being tested. 5 mm is considered a positive reaction in persons with immunosuppressive diseases like HIV or in people taking medications that suppress the immune system, and in patients with recent contact with a Tuberculosis case 10 MM is considered a positive reaction in persons from high prevalence countries for TB, underlying medical problems (diabetes, kidney disease), and certain occupations (health care workers, prisoners, homeless persons 15 mm is considered a positive reaction in very low risk patients. The age of the person tested does not typically determine the interpretation of the test.

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Response by:

Catherine A Curley, MD, MS Catherine A Curley, MD, MS
Assistant Professor of Medicine
School of Medicine
Case Western Reserve University