Smear-positive Pulmonary Tuberculosis with False-negative Loop-mediated Isothermal Amplification and T-SPOT.TB Assays.

Rapid molecular and immunological assays for tuberculosis, including loop-mediated isothermal amplification (LAMP) and T-SPOT.TB assays, may yield false-negative results. We herein report a 62-year-old immunocompetent man with a productive cough, elevated C-reactive protein (22.8 mg/dL) and procalcitonin (2.7 ng/mL) levels, and computed tomography findings suggestive of nontuberculous mycobacterial infection. Despite the acid-fast bacilli-positive smears, two separate Mycobacterium tuberculosis LAMP assays and a T-SPOT.TB assay were negative. Empirical treatment with ampicillin/sulbactam and erythromycin improved the patient's condition. Four-week cultures confirmed pulmonary tuberculosis. This case underscores the importance of interpreting rapid assays within the clinical context and supports the use of reflex polymerase chain reaction for a definitive diagnosis.