Niwa N, et al. - The relationship between purified protein derivative (PPD) skin test reactions before bacillus Calmette-Guérin (BCG) therapy and the clinical outcomes of BCG-naïve non-muscle invasive bladder cancer patients treated with adjuvant BCG therapy was determined. In the current study it was shown that before BCG therapy, PPD skin test reactions are predictive of clinical outcomes following BCG therapy and help clinicians counsel patients exhibiting strong therapeutic effects with BCG therapy and potentially major BCG-related side effects.