Which of the following can lead to a false positive PPD test result?

A false positive result in a Purified Protein Derivative (PPD) test, also known as a tuberculin skin test, can occur due to several factors, with BCG vaccination being a significant contributor. The Bacillus Calmette-Guérin (BCG) vaccine is given in many countries to prevent tuberculosis, particularly in children. Because the vaccine contains live, attenuated strains of Mycobacterium bovis, it can stimulate a cell-mediated immune response similar to that caused by Mycobacterium tuberculosis, thus leading to a positive PPD test even in the absence of an actual TB infection.

This response can complicate interpretation, particularly in individuals who have received the BCG vaccine, as their immune systems may react to the tuberculin compared to people who have not been vaccinated.

In contrast, an acute TB infection itself would typically lead to a true positive result. Previous exposure to tuberculosis would also usually result in a true positive because the immune system retains memory responses to the tuberculin antigen. Improper reading technique could lead to variability in testing results but is less commonly a direct cause of false positives compared to the impact of BCG vaccination. Understanding the implications of BCG vaccination on PPD testing is essential