Tuberculosis
Laboratory investigations
Mantoux test
0.1 ml of 1:1,000 purified protein derivative (PPD) injected intradermallyDiameter of area measured 2-3 days later
Diameter | Interpretation | |
<6mm | Negative | Not exposed |
6-15mm | Positive | Suggests infection or previous BCG |
>15mm | Strongly positive | Suggests active infection |
(NB false negatives in HIV, lymphoma, age <6 months, sarcoidosis
Interferon gamma assays
Recommended if Mantoux is positive, and can discriminate positive Mantoux due to BCG from latent TB.
Management
page revision: 6, last edited: 12 Apr 2017 15:26