Sputum Test Results Interpretation for Pulmonary TB
Diagnostic Interpretation | Clinical Implication | |||
|---|---|---|---|---|
Positive | Negative | Positive | TB | Initiate treatment for TB. |
Negative | Positive | Positive | TB | Initiate treatment for TB. |
Negative | Negative | Positive | TB | Initiate treatment for TB. |
Negative | Negative | Negative | Most common results No TB | Treatment for TB not indicated Consider evaluation/treatment for latent TB if clinically indicated. |
Positive | Positive | Negative | Highly suggestive of TB Negative culture result could mean NTM infection or low bacterial load | Initiate treatment for TB. |
Negative | Positive | Negative | Less common results Possibly low Mycobacterium tuberculosis levels or early-stage TB Usually requires repeat testing and clinical evaluation | Repeat sputum for AFB smear and NAAT. If 2 specimens are NAAT-positive, consider treatment for presumed TB based on clinical setting. |
Positive | Negative | Negative | Extremely rare results Possibly NTM infection or contamination, not M. tuberculosis | Repeat sputum for AFB smear and NAAT. If second smear is positive and NAAT is negative, presumed NTM infection. |
AFB = acid-fast bacilli; NAAT = nucleic acid amplification test; NTM = nontuberculous mycobacterial; TB = tuberculosis. | ||||