Tuberculosis: Screening

Key points

• The Mantoux test is the main technique used to screen for latent tuberculosis. In recent years the interferon-gamma blood test has also been introduced. It is used in a number of specific situations such as:
• the Mantoux test is positive or equivocal
• people where a tuberculin test may be falsely negative (see below) Mantoux test
• 0.1 ml of 1:1,000 purified protein derivative (PPD) injected intradermally
• result read 2-3 days later Diameter of induration Positivity Interpretation < 6mm Negative - no significant hypersensitivity to tuberculin protein Previously unvaccinated individuals may be given the BCG 6 - 15mm Positive -…