title: Mycobacterium tuberculosis complex detected by modified fluorescent in situ hybridization in lymph nodes of clinical samples.
abstract: BACKGROUND
  Lymph node tuberculosis (TB) is the leading cause of extrapulmonary tuberculosis and is the most frequently identified type in Aguascalientes, Mexico. Conventional diagnosis has serious limitations for rapid detection of extrapulmonary tuberculosis in clinical samples. Here PCR and modified FISH have been tested as complementary diagnosis methods for extrapulmonary tuberculosis.
  
  
  METHODS
  The specific insertion sequence IS6110 for Mycobacterium tuberculosis complex was used to perform PCR and build DNA and PNA FISH probes (20bp). PCR and modified DNA and PNA FISH assays were performed to evaluate 41 lymph node paraffin-embedded tissue samples, in comparison with the histopathology diagnosis, which was considered the gold standard (22 positive and 19 negative).
  
  
  RESULTS
  In comparison with histopathology diagnosis PCR showed 62.5 % sensitivity and 77.8 % specificity (χ(2) = 4.583 p < 0.05). Modified DNA FISH showed 71.4% sensitivity and 84.6% specificity (χ(2) = 11.21 p < 0.05). PNA FISH showed 66.7% sensitivity and 60.0% specificity (χ(2) = 2.93 p > 0.05). Ziehl Neelsen stain was positive in only four cases of 22 lymph node samples positive to histopathology.  In contrast, PCR and modified DNA FISH were positive in 20 cases of the same group. The negative cases were coincident in all tests.
  
  
  CONCLUSIONS
  PCR and DNA FISH showed a significant increase in the number of cases detected and also showed higher sensitivity and specificity compared with data reported by traditional methodology. In developing countries, these techniques could help to complement the early diagnosis and timely treatment of extrapulmonary tuberculosis.
authors.affiliation: Universidad Autónoma de Aguascalientes, Aguascalientes, México. mdjuandelacruz@hotmail.com
authors.forename: Juan
authors.initials: J
authors.lastname: Rodriguez-Nuñez
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Avelar
authors.forename: Francisco
authors.initials: F
authors.lastname: Marquez
authors.forename: Bruno
authors.initials: B
authors.lastname: Rivas-Santiago
authors.forename: Cesar
authors.initials: C
authors.lastname: Quiñones
authors.forename: Alma L
authors.initials: AL
authors.lastname: Guerrero-Barrera
mesh_terms: D015342:DNA Probes; D004251:DNA Transposable Elements / Q000235:genetics*; D004269:DNA, Bacterial / Q000032:analysis / Q000235:genetics; D006801:Humans; D017404:In Situ Hybridization, Fluorescence / Q000379:methods*; D008198:Lymph Nodes / Q000382:microbiology* / Q000473:pathology; D008800:Mexico; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000302:isolation & purification*; D016612:Paraffin Embedding; D020135:Peptide Nucleic Acids / Q000235:genetics; D016133:Polymerase Chain Reaction / Q000379:methods; D012680:Sensitivity and Specificity; D014388:Tuberculosis, Lymph Node / Q000175:diagnosis* / Q000382:microbiology
chemical_list: D015342:DNA Probes; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D020135:Peptide Nucleic Acids