title: Diagnostic utility of QuantiFERON-TB gold in-tube in active pulmonary Tuberculosis in Nigeria.
abstract: BACKGROUND
  The high positive responses obtained in active TB indicate that IGRAs may be useful in diagnosing active TB. This study aimed at evaluating the usefulness of Quantifer on-TB Gold-in Tube test (QFT-IT) in the diagnosis of active TB among Nigerians.
  
  
  METHODS
  This study prospectively enrolled sputum smear positive TB cases and healthy disease free controls. Basic demographic and clinical data were collected using a structured questionnaire. Venous blood was collected into the QTF-IT tubes, incubated for 16-24 hours, serum harvested and stored at -200C till analysed in a batch. Tuberculin skin test (TST) was also done using 5TU and read within 48-72 hours. The performances of QFT-IT and TST among the cases and controls were compared.
  
  
  RESULTS
  Sixty one TB cases and 41 controls were enrolled. The mean (SD) age of the TB cases was higher than the controls, 35.14+4.3 yrs v 27.8 + 2.1, p<0.001. Forty three (70.5%), 13 (21.3%) and 5 (8.2%) of the cases had a positive, negative and indeterminate QFT-IT results respectively compared with 14 (34.1%), 25 (61%), and 2 (4.9%) of the controls respectively, p values <0.001, 0.005 and 0.05 respectively. Fifty eight(95%) and 29(70.7%) of the TB cases and controls had a positive TST result respectively while 3 (5%) and 12( 29.3%) of the TB cases and controls had a negative TST result respectively, p values 0.003 each .QFT-IT had a sensitivity of 76% (95% CI 61.8 -85.2%) while the sensitivity of TST was 96.6% (95% CI 88.5 -98.3%), p = 0.07. The specificity of QFT-IT was 63.7% (95% CI 46-76%) and 30% (95% CI 20- 56%) for TST, p =0.001. Positive Likelihood ratio was 1.7 (95% CI 1.06-2.85) for QFT-IT and 1.4 (95%CI 1.06-1.8) for TST, p =0.002. Among the cases, both TST and QFT-IT were positive in 43(70.5%) and both negative in 1 (1.6%), and overall test .agreement was 77.7% (Kappa =0.13; p= 0.07). Female sex and higher total lymphocytes count were significantly associated with a positive QFT results.
  
  
  CONCLUSIONS
  IGRA has a higher specificity and positive likelihood ratio in TB cases. Our findings indicate that QFT-IT may be a good adjunct tool to diagnose TB disease.
authors.affiliation: Department of Medicine, Obafemi Awolowo University, Ile Ife, Nigeria.
authors.forename: O O
authors.initials: OO
authors.lastname: Adewole
authors.forename: G E
authors.initials: GE
authors.lastname: Erhabor
authors.forename: M O
authors.initials: MO
authors.lastname: Sogaolu
authors.forename: A O
authors.initials: AO
authors.lastname: Onipede
authors.forename: P K
authors.initials: PK
authors.lastname: Owiafe
authors.forename: F O
authors.initials: FO
authors.lastname: Awopeju
authors.forename: M O C
authors.initials: MO
authors.lastname: Ota
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D059425:Interferon-gamma Release Tests / Q000379:methods*; D008297:Male; D009549:Nigeria; D011446:Prospective Studies; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis*