Diagnosing latent and active pulmonary tuberculosis: a review for clinicians

Tuberculosis (TB) is once again a major public health concern. Primary care providers play a key role in controlling its spread, both by case-finding patients with active TB and providing preventive therapy to persons at high risk for developing it. This article describes the natural history and different stages of illness (latent infection, active disease, and old healed disease) in terms of direct implications for management. Diagnostic tools are examined in detail. Pitfalls in administration and interpretation of tuberculin skin tests are reviewed, including the factors that may cause false-negative and false-positive readings. Radiographic findings are explained and illustrated. Sputum analysis is discussed in detail in terms of specimen collection, laboratory methodologies for performing smears and cultures, and their respective specificity and sensitivity. A basic approach to workup and management is also outlined, distinguishing screening from diagnosis and emphasizing how to identify those persons at greatest risk for TB.