title: A study of tubercular lymphadenitis: a comparison of various laboratory diagnostic modalities with a special reference to tubercular polymerase chain reaction.
abstract: OBJECTIVE
  The purpose of our study was to compare various laboratory diagnostic methods, namely histopathological examination, Ziehl-Neelsen (ZN) stain, AFB culture by conventional Lowenstein-Jensen (LJ) method and fluorescence-based mycobacterial growth indicator tube (MGIT) technique and polymerase chain reaction (PCR) in clinically suspected cases of tubercular lymphadenitis.
  
  
  METHODS
  A total of 65 lymph nodes biopsied from patients clinically suspected of having tubercular lymph nodes were included. Specimens were processed for AFB culture after NaOH-NALC concentration and inoculation on LJ medium and using the MGIT system. PCR was performed on all specimens using a commercial nested PCR kit targeting IS6110 insertion element of Mycobacterium tuberculosis complex. All lymph node specimens were subjected to histopathological examination.
  
  
  RESULTS
  Of the 65 lymph nodes, 37 (56.9%) were positive on MGIT culture and 45 (69.2%) were positive by PCR. Histopathology showed maximum sensitivity (96%) but with compromised specificity (78.5%). PCR showed 90.1% sensitivity and 100% specificity. The mean turnaround time for mycobacterial growth in smear negative specimens was 30 days determined by LJ and 20 days by MGIT techniques.
  
  
  CONCLUSIONS
  PCR is a rapid and useful method for diagnosis of TB lymphadenitis and definitely increases the positive predictive value of a positive histopathology report. MGIT is better than LJ culture as regards time to positivity and higher yield.
authors: Consultant Microbiologist, Deenanath Mangeshkar Hospital and Research Centre, Erandawane, Pune, India. sampada.patwardhan@gmail.com
authors: S A
authors: SA
authors: Patwardhan
authors: P
authors: P
authors: Bhargava
authors: V M
authors: VM
authors: Bhide
authors: D S
authors: DS
authors: Kelkar
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001431:Bacteriological Techniques / Q000379:methods*; D001706:Biopsy; D002648:Child; D002675:Child, Preschool; D005260:Female; D006651:Histocytochemistry; D006801:Humans; D007223:Infant; D008198:Lymph Nodes / Q000382:microbiology; D008297:Male; D008875:Middle Aged; D025202:Molecular Diagnostic Techniques / Q000379:methods*; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000302:isolation & purification*; D016133:Polymerase Chain Reaction / Q000379:methods*; D012680:Sensitivity and Specificity; D014388:Tuberculosis, Lymph Node / Q000175:diagnosis*; D055815:Young Adult