BCG vaccination may cause a false positive PPD result.

BCG vaccination may cause a false positive PPD result.

• A. It never affects PPD results
• B. It always causes a false positive PPD result
• C. It only affects PPD in children
• D. It may cause a false positive PPD result

Answer: (D)

BCG vaccination can cause cross-reactivity in the tuberculin skin test (PPD) because the vaccine uses mycobacterial antigens that resemble those in PPD. This means a person who has been vaccinated may develop a positive PPD response even if they have not been infected with TB. However, this isn’t guaranteed for everyone or at all times; the likelihood depends on factors like when the vaccine was given, the vaccine strain, and time since vaccination. That’s why the statement that it may cause a false positive PPD result is the most accurate. In practice, clinicians consider this possibility and may use interferon-gamma release assays to help distinguish true TB infection from BCG-induced reactivity, especially in those with a history of vaccination. The other options are incorrect because the effect is not absolute, not limited to children, and not nonexistent.

BCG vaccination can cause cross-reactivity in the tuberculin skin test (PPD) because the vaccine uses mycobacterial antigens that resemble those in PPD. This means a person who has been vaccinated may develop a positive PPD response even if they have not been infected with TB. However, this isn’t guaranteed for everyone or at all times; the likelihood depends on factors like when the vaccine was given, the vaccine strain, and time since vaccination. That’s why the statement that it may cause a false positive PPD result is the most accurate. In practice, clinicians consider this possibility and may use interferon-gamma release assays to help distinguish true TB infection from BCG-induced reactivity, especially in those with a history of vaccination. The other options are incorrect because the effect is not absolute, not limited to children, and not nonexistent.