title: [Analysis of patients with positive acid-fast bacilli culture and negative T-SPOT.TB results].
abstract: BACKGROUND
  T-SPOT.TB is a sensitive test that detects interferon-gamma producing T-cells in tuberculosis patients following stimulation with tuberculosis-specific antigens. Our study was aimed to investigate the possible causes of false negative results of the test by analyzing the patients with positive acid-fast bacilli (AFB) culture and negative T-SPOT.TB results.
  
  
  METHODS
  We investigated 138 patients with positive AFB culture results reported between January 2009 and April 2010. Medical records of these patients were reviewed for the results of T-SPOT.TB test, AFB culture, PCR for Mycobacterium tuberculosis (TB-PCR), chest X-ray, drug treatment, etc. Diagnosis of tuberculosis was confirmed by positive TB-PCR or identification of Mycobacterium tuberculosis (MTB). Sensitivity of T-SPOT.TB test was calculated and the possible causes of AFB culture positive and T-SPOT.TB negative results were analyzed.
  
  
  RESULTS
  T-SPOT.TB test was performed in 63 of the 138 patients with AFB culture positive results. Fifty-six (88.9%) were positive and 7 patients (11.1%) were negative on T-SPOT.TB test. Of these 7 negative cases, 4 were confirmed as nontuberculous mycobacteria (NTM), 2 were suspected as NTM and diagnosis could not be confirmed in 1. Six of these 7 patients were over 70 yr old and 6 patients had lymphocytopenia. T-SPOT.TB negative results were not observed in any of the 44 patients confirmed to have active tuberculosis (sensitivity 100%).
  
  
  CONCLUSIONS
  Our results suggest that T-SPOT.TB test is very sensitive for diagnosing active tuberculosis. NTM may be the main cause of AFB culture positive and T-SPOT.TB negative results, but MTB infection in immunocompromised patients also has to be considered.
authors.affiliation: Department of Radiology, Hallym University College of Medicine, Seoul, Korea.
authors.forename: You Mie
authors.initials: YM
authors.lastname: Han
authors.forename: Hyun Soo
authors.initials: HS
authors.lastname: Kim
authors.forename: Cheol Hong
authors.initials: CH
authors.lastname: Kim
authors.forename: Hee Jung
authors.initials: HJ
authors.lastname: Kang
authors.forename: Kyu Man
authors.initials: KM
authors.lastname: Lee
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001407:Bacillus / Q000302:isolation & purification*; D003470:Culture Media; D005260:Female; D006801:Humans; D018655:Lymphocyte Count; D008231:Lymphopenia / Q000175:diagnosis / Q000382:microbiology; D008297:Male; D016133:Polymerase Chain Reaction; D011859:Radiography; D011933:Reagent Kits, Diagnostic; D012680:Sensitivity and Specificity; D014376:Tuberculosis / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000382:microbiology
chemical_list: D003470:Culture Media; D011933:Reagent Kits, Diagnostic