People also ask
How many MM is a negative TB test?
An induration of less than 5 millimeters (mm) is considered a negative test result. If you have symptoms or you know you've been exposed to someone with TB, you may be advised to get another test later.
What number is a positive TB test?
You're considered positive if your bump is: Greater than or equal to 5 millimeters (mm) and you have a compromised immune system. Equal to 10 mm and you're a healthcare worker. Equal to 15 mm and you don't have any risk factors.
What does induration mean for TB test?
"Reading" the skin test means detecting a raised, thickened local area of skin reaction, referred to as induration. Induration is the key item to detect, not redness or bruising. Read skin tests 48-72 hours after the injection when the size of the induration is maximal.
How do nurses test for TB skin?
The nurse will inject a small amount of fluid just under the skin of the left forearm. You will see a little bubble or blister appear right away at the injection site. This is normal and it will soon disappear. After 2-3 days, you will be asked to see the nurse to have the area checked and the reaction measured.
What is the measurement of a positive TB skin test?
* For employees who are otherwise at low risk for TB and who are tested as part of an infection control screening program at the start of employment, a reaction of 15 mm is considered positive.
tb skin test form template