Table 2 Diagnostic tests for pulmonary tuberculosis: current, under evaluation and in development
From: The role of rapid diagnostic tests in managing adults with pneumonia in low-resource settings
Test | Comments | Ref |
|---|---|---|
Chest radiography | Used as adjunct to smear microscopy. No radiographic pattern diagnostic of TB and substantial inter-observer variation. Appearances vary with immune status in HIV-associated disease. | |
Sputum smear microscopy | Rapid and widely available; often sole diagnostic test. Sensitivity is poor, particularly in HIV-associated TB; increased by sputum concentration and fluorescence microscopy rather than ZN staining. | |
Sputum culture | Gold-standard diagnostic test; often restricted to reference centres in resource-limited settings. Automated liquid culture systems (e.g. BACTEC MGIT 960; Becton Dickinson, USA) are faster and more sensitive than solid culture techniques. | |
Xpert MTB/RIF (Cepheid, USA) | Fully automated NAAT platform; allows rapid detection of MDRTB. More sensitive than sputum smear microscopy, particularly in HIV-infection. High setup and running costs; needs uninterrupted electrical supply. | |
Line probe assay (e.g. GenoType MTBDRplus 2.0; Hain Lifescience GmbH, Germany) | NAAT mainly used for rapid identification of isoniazid mono-resistance and MDRTB in culture isolates. Now adapted for use on clinical specimens; comparable accuracy to Xpert MTB/RIF. | |
Loop-mediated isothermal amplification | Simplified, manual NAAT for use in basic laboratory settings. Currently in large scale evaluation; estimated sensitivity is 88% overall and 56% in sputum smear-negative TB. | |
Urinary lipoarabinomannan (e.g. Alere Determine TB LAM Ag; Alere, USA) | POC assay facilitating rapid treatment initiation. Most sensitive in advanced HIV-infection; incremental increase in sensitivity over sputum smear microscopy and Xpert MTB/RIF alone. | |
Volatile organic compounds | Mass spectrographic analysis of exhaled breath for compounds associated with pulmonary TB. In early stages of development; requires sophisticated instrumentaion. | |
Serological tests | Humoral response to TB is highly variable; no single antibody measurement proved useful in diagnosis. Assays based on simultaneous detection of multiple antibodies in development. | |
Proteomics | Serum proteomic profile of active TB derived by mass spectrometry. Diagnostic tests based on candidate biomarkers in development. |