The diagnostic approach for suspected tuberculosis involves a combination of clinical evaluation, imaging studies, and laboratory tests, which vary depending on whether pulmonary or extrapulmonary tuberculosis is suspected.
Pulmonary tuberculosis
- Chest imaging: Chest X-ray (CXR) is recommended as the first-line imaging in patients with suspected tuberculosis. If the CXR is non-revealing or nondiagnostic, a chest CT may be obtained
- Nucleic acid amplification testing (NAAT): The World Health Organization (WHO) 2021 guidelines recommend obtaining Xpert MTB/RIF or Xpert Ultra as an initial test for pulmonary tuberculosis in adult patients with signs and symptoms of tuberculosis . The American Thoracic Society/Centers for Disease Control and Prevention/Infectious Diseases Society of America (ATS/CDC/IDSA) 2017 guidelines also recommend obtaining an NAAT on the initial respiratory specimen obtained from patients with suspected pulmonary tuberculosis
- Smear and culture: Both liquid and solid mycobacterial cultures are recommended for every specimen obtained from patients with suspected tuberculosis
Extrapulmonary tuberculosis
- Blood/skin tests: A purified protein derivative skin test and an interferon-gamma release assay (IGRA) are recommended in patients with suspected spondylodiscitis and risk factors for Mycobacterium tuberculosis . These tests are also recommended in patients with subacute native vertebral osteomyelitis at risk for Mycobacterium tuberculosis
- Nucleic acid amplification testing (NAAT): An NAAT is recommended on synovial fluid specimens in patients with suspected tuberculous arthritis
- Mycobacterial culture: Mycobacterial culture is recommended on synovial fluid specimens in patients with suspected tuberculous arthritis
- Tissue biopsy: A synovial biopsy for culture and histopathological analysis is recommended in patients with suspected tuberculous arthritis
- Fluid specimen analysis: Analysis for cell count and differential, protein, glucose, pH, LDH, and cytology on pleural effusion/pleural fluid is recommended in patients with suspected tuberculosis
Screening for latent tuberculosis
- Systematic testing for latent tuberculosis infection is recommended in certain high-risk groups, including prisoners, health workers, immigrants from countries with a high tuberculosis burden, homeless persons, and people who use drugs
- Testing is also recommended in patients initiating anti-TNF treatment, receiving dialysis, preparing for an organ or hematological transplant, or having silicosis
In conclusion, the diagnostic approach for suspected tuberculosis involves a combination of clinical evaluation, imaging studies, and laboratory tests, which vary depending on whether pulmonary or extrapulmonary tuberculosis is suspected. Systematic testing for latent tuberculosis infection is also recommended in certain high-risk groups.