Mantoux Test

Last Sunday I had medical check-up for university purpose. A funny incident happened when I had a medical test which is called mantoux test. For your information, the mantoux test is used to detect latent TB infection ( future risk of developing TB) or any other fatal diseases. I'm sure every student have had the experienced of going through the injection process. Patients that have been injected must wait another 3 days ( 72 hours) to get the result by measuring the hard and dense induration on their skin. The tuberculin is injected into the first layer of our skins not into the blood vien. The normal range is from 0mm to 15mm.On the third day, I have to see the doctor in the evening for the result but the red mark on my skin is so big, really made me nervous of the thought of being infected by TB. I told my parents and they stunned too. I measured it using my old school ruler and oh my god, the reading is 20mm..it's mean I've positive TB and of course I have to postpone my studies and everything will ruin as well...but looking back at myself..I never look sick or feeling that way...I looked deeply on the red mark..I saw a small clear induration in the middle of it..what is it?..I searched mantoux test in the internet and I found one thing that made me feel I'm a dimwit...huhu.. ' measure only the induration, which is hard , dense , and raised formation not the redness around it'...If i read it earlier..(T_T)..haha the doctor also did same thing as in the internet..so next time I won't let such thing happen again.. hahaha