Tuberculosis( Positive)?

how do you know if a TB skin Test Is Positive???

The skin test(PPD test) will basically tell you that,whether, you have developed immune response to the bacterium that causes Tuberculosis. Once, you had your test done, the result should be red between 48-72 hours. Anything greater than 72 hours will give you false positive or false negative results.

What, you have to look for in the skin test is, the "induration"(the thickened ,raised skin area...NOT the reddened area on the skin). Here, you measure the diameter of the induration transversely to the long axis of the forearm and record in millimetre.

Here, how you interpret the results,

In a healthy person, if the induration measures equal or greater than 15mm, it is considered positive.

Person working in the health care field or who lives in a endemic area(TB prevalent area), person with kidney disease and diabetic, 10mm of induration is considered positive.

5mm of induration is considered positive if, the person is immunocompromised, person with crohn`s disease and rheumatoid arthritis.

Anything less than 2 mm is considered negative.

Please do remember, skin test is not a confirmatory test. It should be judged against other risk factors that,make the person vulnerable to the TB.

Hope, this helps,

Regards,