title: Significance of interferon-gamma response to mitogen in serial QuantiFERON-TB Gold In-Tube assay of routine laboratory practice.
abstract: BACKGROUND
  Clinical data of serial interferon-γ release assay (IGRA) testing in routine laboratory practice are limited. IFN-γ response to mitogen is used as a positive control in IGRA. We assessed the association between IFN-γ response to nil, mitogen, tuberculosis (TB) mycobacterial antigens, and the variations from the results of the serial testing.
  
  
  METHODS
  A total of 299 patients with serial QuantiFERON-TB Gold In-Tube (QFT-GIT) were enrolled. The medical records of patients were reviewed for demographic information, status of Mycobacterium tuberculosis infection, treatment of tuberculosis, and the quantitative response to nil, mitogen, and TB antigen.
  
  
  RESULTS
  The initial QFT-GIT result was positive in 142 patients (47.5%), negative in 139 (46.5%), and indeterminate in 18 (6.0%). Of total, 79.6% showed concordant results in serial testing. The discordance in serial tests was significantly high in patients with a low mitogen response (≤ 3.93 IU/ml) (p<0.0001). Quantitative TB responses around the cut-off point in serial QFT-GIT were associated with an increased conversion and reversion rates (p = 0.01, p = 0.0005), respectively.
  
  
  CONCLUSIONS
  Because IGRAs are dynamic assays, integrated interpretation of quantitative TB response with mitogen and nil response would be helpful in serial QFT-GIT. Recommendations for the interpretation of results of serial testing for active TB will be required.
authors.affiliation: Department of Laboratory Medicine, Dong-A University College of Medicine, Busan, Republic of Korea.
authors.forename: Kwang-Sook
authors.initials: KS
authors.lastname: Woo
authors.affiliation: Department of Laboratory Medicine, Dong-A University College of Medicine, Busan, Republic of Korea.
authors.forename: Jae-Lim
authors.initials: JL
authors.lastname: Choi
authors.affiliation: Department of Laboratory Medicine, Dong-A University College of Medicine, Busan, Republic of Korea.
authors.forename: Bo-Ram
authors.initials: BR
authors.lastname: Kim
authors.affiliation: Department of Laboratory Medicine, Dong-A University College of Medicine, Busan, Republic of Korea.
authors.forename: Ji-Eun
authors.initials: JE
authors.lastname: Kim
authors.affiliation: Department of Preventive Medicine, Dong-A University College of Medicine, Busan, Republic of Korea.
authors.forename: Byoung-Gwon
authors.initials: BG
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine, Dong-A University College of Medicine, Busan, Republic of Korea.
authors.forename: Hyuck
authors.initials: H
authors.lastname: Lee
authors.affiliation: Department of Laboratory Medicine, Dong-A University College of Medicine, Busan, Republic of Korea. Electronic address: progreen@dau.ac.kr.
authors.forename: Kyeong-Hee
authors.initials: KH
authors.lastname: Kim
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D019411:Clinical Laboratory Techniques; D005260:Female; D006801:Humans; D007223:Infant; D007371:Interferon-gamma / Q000276:immunology*; D059425:Interferon-gamma Release Tests; D008297:Male; D008875:Middle Aged; D008934:Mitogens / Q000276:immunology*; D012015:Reference Standards; D012984:Software; D014376:Tuberculosis / Q000175:diagnosis / Q000276:immunology* / Q000382:microbiology; D055815:Young Adult
chemical_list: D008934:Mitogens; D007371:Interferon-gamma
keywords: Conversion; Mitogen response; Mycobacterium tuberculosis infection; QuantiFERON-TB Gold In-Tube; Reversion; Serial interferon-γ release assay