Discussion

tb postitive?

Jul 18, 200817 yr

Hey guys, I have looked at dozens of tb screens the past few months and am wondering what exactly a positive reaction looks like? I know it is rare, but I work in corrections where a positive is more likely than in general population. I had one the other day that was red and raised slightly, sort of like a spider or bee bite. It was about 1 inch dia., but maybe only a quarter inch high. I asked the other nurses and they said it was probably only a local allergic reaction and I guess another nurse looked at it and said it was fine. I just don't want to pass it off it it was positive. Will a "real" reaction be very obvious and about how big will it be? Any links to pictures would help also as I could'nt find any...

Jul 18, 200817 yr

Yup, that sounds like a positive test.

It gets red pretty quickly.

You'll need a chest x-ray.

Jul 18, 200817 yr

What was the patient's history? If I remember correctly for school, different-sized indurations are positive depending on the individual's risk factors. Unfortunately, I cannot remember the sizes right now...maybe someone else can help out with that? For example, a 5mm induration would be positive in a healthcare worker but it would take 10mm of induration to be positive in someone who is a non-immunocompromised non-healthcare worker...?

Jul 19, 200817 yr

"a 5mm induration would be positive in a healthcare worker but it would take 10mm of induration to be positive in someone who is a non-immunocompromised non-healthcare worker...? "

a positive result for a no tb risk factor person is 15mm and 10mm for healthcare workers, and 5mm is for immunocompromised.

5 mm or more is positive in
- hiv-positive person
- recent contacts of tb case
- persons with nodular or fibrotic changes on chest x-ray consistent with old healed tb
- patients with organ transplants and other immunosuppressed patients

10 mm or more is positive in
- recent arrivals (less than 5 years) from high-prevalence countries
- injection drug users
- residents and employees of high-risk congregate settings (e.g., prisons, nursing homes, hospitals, homeless shelters, etc.)
- mycobacteriology lab personnel
- persons with clinical conditions that place them at high risk (e.g., diabetes, prolonged corticosteroid therapy, leukemia, end-stage renal disease, chronic malabsorption syndromes, low body weight, etc)
- children less than 4 years of age, or children and adolescents exposed to adults in high-risk categories

15 mm or more is positive in
- persons with no known risk factors for tb

Jul 19, 200817 yr

Author

So it sounds like the patient is ok. I believe its less than 10mm, probably more like 5. Seems hard to measure, but it was a somewhat hard area. There was another patient awhile back that had the same type of reaction and an experienced nurse said it was ok. I still wonder if it was just a localized allergic reaction and what a positive reaction would look like...