Do’s and Don’ts of TB Diagnosis

  • TB tests cannot be done from blood
  • TB tests should be done from site specific samples like endometrium, pleural fluid, ascitic fluid etc.
  • For every case of suspected TB, tests to be performed are TB culture and GeneXpert
  • Sputum sample should not be salivary in nature
  • In case a patient is unable to produce sputum, nebulization with hypertonic saline is done. If this fails, a bronchoscopic sample is desired
  • Three consecutive sputum samples are needed for TB culture for better yield
  • Five consecutive urine samples are needed for TB culture for better yield
  • TB gold is not a diagnostic test in cases of suspected TB
  • Tissue samples for GeneXpert and TB culture should be received in saline and not in formalin

As per the WHO’s latest data, India has an average burden of 2.79 million TB cases.

  • Rapid test for detection of M. tuberculosis genome and Rifampicin resistance (detects rpoB gene mutation)
TB Culture
  • TB Culture using MGIT BACTEC (Liquid Based System) is the Gold Standard in diagnosis of tuberculosis
AFB Smear
  • 3 consecutive early morning sputum sample is advisable for AFB smear tests as there could be intermittent shedding of bacteria in sputum.
TB Drug Sensitivity
  • Susceptibility to 13 drugs
1st Line 2nd Line 3rd Line
Streptomycin Kanamycin Ciprofloxacin
Isoniazid Ethionamide Levofloxacin
Rifampicin PAS Amikacin
Ethambutol Moxifloxacin Capreomycin
MTB Detection Test/ TB PCR
  • Targets IS6110 gene which is present in multiple (4-15) copies in TB genome, hence, sensitivity increases in comparison to other gene targets
Cytology/ Biopsy
  • Gross examination procedure by dedicated histopathologist
Adenosine Deaminase (ADA)
  • Rapid test useful in accurate and early diagnosis in patients with extra pulmonary tuberculosis