The CBIC Certified Infection Control Exam Study Guide (6th edition) aligns with CDC guidance regarding interpretation of the tuberculin skin test (TST) in healthcare personnel. For a healthy individual with no known risk factors for tuberculosis, a TST is considered positive only when induration is ≥10 mm. In this scenario, the employee’s TST result of 7 mm induration is negative and does not meet the threshold for latent TB infection.

A prior history of BCG vaccination does not change interpretation criteria in adults. The CDC explicitly recommends that TST results be interpreted regardless of BCG history, as vaccine-related reactivity typically wanes over time and induration should not be attributed to BCG alone. Therefore, a 7 mm reaction in a low-risk, asymptomatic healthcare worker does not require further diagnostic evaluation.

Option A (chest x-ray) is reserved for individuals with a positive TB test or symptoms suggestive of active TB. Option C (repeat testing) is not indicated unless this was part of a two-step baseline test and the first result was negative in a newly hired employee, which is not the case here. Option D is inappropriate because treatment is only considered after confirmed latent TB infection.

For the CIC® exam, it is essential to recognize that no further action is required when TST induration is below the positive threshold for the individual’s risk category, even in those with prior BCG vaccination.