What is the recommended approach to asymptomatic patients who develop a reactive PPD?

Clinical evaluation and chest x-ray are recommended for asymptomatic patients with a positive purified protein derivative (PPD) test result, to exclude the slight possibility of active tuberculosis (TB). Patients with radiographic evidence of old (healed) TB infection should also undergo sputum testing (strength of recommendation [SOR]: C, expert opinion). Treatment with isoniazid (INH) monotherapy (300 mg/d) reduces progression of latent tuberculosis to active disease (SOR: A, large randomized controlled trials [RCT]), with 9 months as the optimal treatment length (SOR: B, derivation from RCTs). A 3-month course of combined rifampin (600 mg/d) and INH (300 mg/d) is equivalent in efficacy to INH monotherapy and is associated with similar rates of toxicity (SOR: A, meta-analysis of RCTs), but this regimen is not included in Centers for Disease Control and Prevention recommendations.