4.6 Diagnosis of extra-pulmonary TB in adults

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15%-20% of the total TB cases comprise of Extra-pulmonary TB (EP TB). Tuberculosis of organs other than the lungs such as pleura, lymph nodes, intestine, genito-urinary tract, joint and bones, meninges of the brain etc., is called as extra-pulmonary TB. Tubercular lymphadenitis and pleural effusion are most common among extra-pulmonary TB. It can occur at any age.

Demonstration of AFB in a smear from extra-pulmonary site is often difficult because of low bacillary load. The diagnosis should be supported with investigations and bacteriological examination where possible. Positive contact history of TB is an indication for suspicion of TB when a patient presents with symptoms. Patients usually present with constitutional features (fever, night sweats, weight loss) and local features related to the site of disease.

4.6.1 Diagnose the case as EPTB using the following diagnostic tools

CB-NAAT (GeneXpert) and Liquid Culture are the preferred diagnostic technologies for microbiological confirmation of EP TB. However, there are a host of special investigations which are helpful in diagnosing extra pulmonary tuberculosis. These may be radiological, cytological/ pathological, biochemical and immunological. Details of all these tests are as under:

Confirmatory Tests:

  • Molecular tests: Xpert MTB/RIF or ULTRA: Samples that can be tested are pleural fluid, pericardial fluid, ascitic fluid (laparoscopic), cerebrospinal fluid (by lumbar puncture), synovial fluid, aspirate (FNAC), tissue, lymph node aspirate, lymph node biopsy and pus. Testing of blood, urine and stool samples are not recommended except under research conditions.

(Note: Currently, these facilities are available only at NTRL & RTRLs. They will be expanded up to district level in a phased manner.)

  • TrueNat will be introduced to test PTB
  • Culture for AFB of bodily fluids: Samples that can be tested are pleural fluid, pericardial fluid, ascitic fluid (laparoscopic), cerebrospinal fluid (by lumbar puncture), urine, aspirate (FNAC) from any solid organ e.g. lymph node, spine, epididymis etc.

Supporting / suggestive tests:

  • Histopathological or cytopathological examination- Detection of caseating granulomas on histopathological examination of the biopsy material obtained from body tissues such as lymph node, peritoneum (laparoscopic), synovium, spine, bone, liver, spleen, genital tract, etc. are strongly suggestive of tuberculosis.
  • Imaging studies using X-Rays, CT Scan, Ultra Sonography, of the involved region or organ, e.g. lung/chest, spine, bone, joint, adrenal gland.
  • Biochemical test, e.g. exudate.
  • Cytological examination of effusions, ascites, CSF fluid, etc.
  • Tuberculin skin test (Mantoux Test)
  • Interferon Gamma Release Assays (IGRA)