title: Role of Xpert MTB/RIF in differentiating tuberculosis from sarcoidosis in patients with mediastinal lymphadenopathy undergoing EBUS-TBNA: a study of 147 patients.
abstract: BACKGROUND
  In patients with intrathoracic lymphadenopathy, differentiating tuberculosis from sarcoidosis is often difficult. We hypothesized that Xpert MTB/RIF assay, a semi-automated hemi-nested PCR would help in this regard.
  
  
  OBJECTIVE
  To evaluate the performance of Xpert MTB/RIF in the differential diagnosis of tuberculosis and sarcoidosis.
  
  
  METHODS
  This was a retrospective analysis of patients with intrathoracic lymphadenopathy who underwent endobronchial ultrasound (EBUS)-guided transbronchial needle aspiration (TBNA), and were diagnosed as either tuberculosis or sarcoidosis. The results of Xpert MTB/RIF assay, tuberculin skin test and endosonographic characteristics (heterogeneous echotexture and coagulation necrosis sign) of the lymph nodes were compared between the two groups.
  
  
  RESULTS
  During the study period, 465 EBUS procedures were performed and a diagnosis of sarcoidosis (n=94) or tuberculosis (n=53) was made in 147 patients. Xpert MTB/RIF was positive in 26 (49.1%) and two (2.1%) patients with tuberculosis and sarcoidosis, respectively. The sensitivity, specificity, positive and negative predictive values of Xpert MTB/RIF in the diagnosis of tuberculosis were 49.1 %, 97.9%, 92.9% and 77.3%, respectively. The presence of any of the four features namely positive Xpert MTB/RIF, positive tuberculin skin test, heterogeneous echotexture of the lymph nodes, or the presence of endosonographic coagulation necrosis sign yielded a sensitivity and negative predictive value of 83.0% and 88.0%, respectively in the diagnosis of tuberculosis versus sarcoidosis.
  
  
  CONCLUSIONS
  Xpert MTB/RIF has good specificity and positive predictive value in the diagnosis of tuberculosis, and is a useful investigation in separating tuberculosis from sarcoidosis.
authors.affiliation: Assistant Professor Dept of Pulmonary Medicine Postgraduate Institute of Medical Education and Research Sector-12 Chandigarh-160012 (India). sahajal@gmail.com.
authors.forename: Sahajal
authors.initials: S
authors.lastname: Dhooria
authors.forename: Nalini
authors.initials: N
authors.lastname: Gupta
authors.forename: Amanjit
authors.initials: A
authors.lastname: Bal
authors.forename: Inderpaul Singh
authors.initials: IS
authors.lastname: Sehgal
authors.forename: Ashutosh Nath
authors.initials: AN
authors.lastname: Aggarwal
authors.forename: Sunil
authors.initials: S
authors.lastname: Sethi
authors.forename: Digambar
authors.initials: D
authors.lastname: Behera
authors.forename: Ritesh
authors.initials: R
authors.lastname: Agarwal
mesh_terms: D000328:Adult; D004269:DNA, Bacterial / Q000235:genetics* / Q000302:isolation & purification; D003937:Diagnosis, Differential; D061765:Endoscopic Ultrasound-Guided Fine Needle Aspiration; D005260:Female; D006801:Humans; D007194:India; D008198:Lymph Nodes / Q000382:microbiology / Q000473:pathology; D000072281:Lymphadenopathy / Q000175:diagnosis* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000235:genetics* / Q000302:isolation & purification; D011237:Predictive Value of Tests; D060888:Real-Time Polymerase Chain Reaction; D015203:Reproducibility of Results; D012189:Retrospective Studies; D017565:Sarcoidosis, Pulmonary / Q000175:diagnosis* / Q000473:pathology; D014374:Tuberculin Test; D014388:Tuberculosis, Lymph Node / Q000175:diagnosis* / Q000235:genetics / Q000382:microbiology / Q000473:pathology; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis* / Q000235:genetics / Q000382:microbiology / Q000473:pathology
chemical_list: D004269:DNA, Bacterial
keywords: GeneXpert; endobronchial ultrasound; endoscopic ultrasound; pcr; sarcoidosis; tuberculosis