In an adult, what is the standard maximum induration size for a negative Mantoux test?

The standard maximum induration size for a negative Mantoux test in adults is 10 mm. This is based on guidelines established for interpreting the results of the tuberculin skin test, which is used to determine if someone has been infected with the tuberculosis bacteria. An induration of 10 mm or less is generally interpreted as negative in otherwise healthy adults who are not at high risk for tuberculosis.

The 10 mm cutoff is significant because it represents a threshold where further evaluation may not be necessary for most individuals without specific risk factors. Individuals with conditions such as HIV infection, recent contacts with infectious TB cases, or immunosuppression may have different criteria for a positive test result, but for the general adult population, 10 mm marks the boundary between a negative and a positive test.

In summary, when interpreting the Mantoux test, an induration of 10 mm or less indicates a non-reactive result in adults, signaling that there is no significant exposure or infection with tuberculosis.