title: Comparison of interferon gamma release assay & tuberculin skin tests for diagnosis of latent tuberculosis in patients on maintenance haemodialysis.
abstract: OBJECTIVE
  Tuberculosis (TB) is a common infection in patients on haemodialysis. There is a definite role of treatment of latent TB (LTB) in these patients. However, diagnosis of LTB in these patients by tuberculin skin test (TST) is unreliable. There is suggestion that interferon gamma release assay (IGRA) will be more reliable test for diagnosis of LTB in this setting. Thus, we evaluated value of IGRA and TST for the diagnosis of LTB in patients on dialysis in an Indian setting.
  
  
  METHODS
  Patients with end stage kidney disease on dialysis were included. Patients with active TB were excluded. Each patient was subjected to TST (induration of ≥10 mm was taken as positive) and QuantiFERON TB Gold In-Tube test (QFT-GIT) for diagnosis of LTB.
  
  
  RESULTS
  A total of 185 patients were included; 129 (69.7%) were males and mean age was 36.7 ± 12.3 yr. Past history of TB was present in 18 (9.7%) patients. One hundred and thirty four (72.4%) patients had scar of BCG vaccination. QFT-GIT test was positive in 66 (36%), TST in 32 (17%) and both in 13 (7%) patients. Of the 66 patients positive with QFT-GIT, only 13 (19.6%) were positive for TST. Of the 32 patients positive with TST, only 13 (40.6%) were positive with QFT-GIT; 100 (54%) patients were negative for both the tests. Overall, 85 (45.9%) patients were positive for either of the two tests. Poor agreement was shown between the two methods. On logistic regression analysis, odds of QFT-GIT to be positive in patients with BCG vaccination was 1.23 and with history of TB 0.99, both being insignificant. odds of tuberculin skin test to be positive in patients with BCG vaccination was 1.04 and with history of TB 0.99, both again being insignificant.
  
  
  CONCLUSIONS
  Our findings showed that more number of patients (36%) on haemodialysis were positive for QuantiFERON Gold In-Tube test as compared to TST (17%). There was poor agreement between the two tests. No significant effect of BCG vaccination and history of TB in past was observed on both tests.
authors.affiliation: Department of Nephrology, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Sanjay K
authors.initials: SK
authors.lastname: Agarwal
authors.forename: Urvashi B
authors.initials: UB
authors.lastname: Singh
authors.forename: Sabahat H
authors.initials: SH
authors.lastname: Zaidi
authors.forename: Sanjay
authors.initials: S
authors.lastname: Gupta
authors.forename: Ravinder M
authors.initials: RM
authors.lastname: Pandey
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001500:BCG Vaccine; D005260:Female; D006801:Humans; D007194:India; D007371:Interferon-gamma / Q000378:metabolism*; D059425:Interferon-gamma Release Tests; D007676:Kidney Failure, Chronic / Q000473:pathology; D055985:Latent Tuberculosis / Q000175:diagnosis* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D006435:Renal Dialysis / Q000009:adverse effects*; D014374:Tuberculin Test
chemical_list: D001500:BCG Vaccine; D007371:Interferon-gamma