Single-step QuantiFERON screening of adult contacts: a prospective cohort study of tuberculosis risk
- Pranabashis Haldar1,2,
- Helen Thuraisingam1,
- Hemu Patel3,
- Nelun Pereira3,
- Robert C Free2,
- James Entwisle1,
- Martin Wiselka4,
- Edwyn Wren Hoskyns5,
- Philip Monk6,
- Michael R Barer2,3,*,
- Gerrit Woltmann1,*
- 1Department of Respiratory Medicine, Institute for Lung Health, Glenfield Hospital, Leicester, UK
- 2Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, UK
- 3Department of Microbiology, Leicester Royal Infirmary, Leicester, UK
- 4Department of Infectious Diseases, Leicester Royal Infirmary, Leicester, UK
- 5Department of Paediatrics and Neonatal Medicine, Leicester Royal Infirmary, Leicester, UK
- 6Health Protection Agency, East Midlands South Health Protection Unit, Leicester, UK
- *Cosenior authorship for manuscript.
- Correspondence to Dr Pranab Haldar, Department of Respiratory Medicine, Glenfield Hospital, Groby Road, Leicester, LE3 9QP, UK;
- Received 16 August 2011
- Revised 6 August 2012
- Accepted 9 August 2012
- Published Online First 6 September 2012
Background The efffectiveness of tuberculosis (TB) contact screening programmes using interferon γ release assays remains uncertain as prospective contact TB risk is not well characterised.
Objectives To quantify 2-year TB risk and evaluate screening performance with single-step QuantiFERON TB Gold-In Tube (QFT) in adult contacts. To compare TB risk between QFT tested subgroups stratified by exposure type (smear positive pulmonary (SP) versus non-smear positive (NSP) TB) and age (younger (16–35 years) versus older (≥36 years)).
Methods Screening involved QFT testing in older contacts of SP and all younger contacts, 8–12 weeks after index notification. Chemoprevention (3RH) was offered to QFT positive (+) younger adults. TB risk was determined in a prospective cohort study.
Results 43 TB events occurred in 1769 adult contacts observed for median 717 days (2-year rate (95% CI)=2·5% (1.7 to 3.2)). Index-contact strain matching was demonstrable for 18 of 22 (82%) paired samples. No contacts (0/98) receiving 3RH developed TB. 215 of 817 appropriately tested adults (26.3%) were QFT+. 14 of 112 untreated QFT+ adults developed TB (2-year rate (95% CI)=13·4% (7.7 to 21.1)). The model required 35 contacts screened with QFT to identify one contact developing TB at 2 years. TB rates were comparable in QFT+ contacts of SP and NSP (rate ratio (RR)=0.98, p=0·962). For QFT+ older contacts, the disease rate was lower (8.9% (3.3 to 19.1)) and similar to the overall group rate (RR=1.4, p=0.503).
Conclusions QFT based single-step contact screening is effective in young adults.