Interferon- gamma release assays do not identify more children with active TB than TST

¹ Academic Dept of Paediatric Infectious Diseases, Imperial College London; Wellcome Centre for Clinical Tropical Medicine, Imperial College London; and Centre for Respiratory Infection, Imperial College London
² Academic Dept of Paediatric Infectious Diseases, Imperial College London
³ Dept of Paediatrics, Northwest London Hospital Trusts, Northwick Park, London
⁴ Imperial College NHS Trust, St. Mary's Campus, London
⁵ Wellcome Centre for Clinical Tropical Medicine, Imperial College London
⁶ MRC Clinical Trials Unit, MRC, Euston Road, London
⁷ Academic Dept of Paediatric Infectious Diseases, Imperial College London; and Brighton and Sussex Medical School, University of Sussex, Falmer, Brighton BN1 9PS, UK

^* To whom correspondence should be addressed. E-mail: b.kampmann{at}imperial.ac.uk.

	Abstract

Data are lacking on the performance of Interferon-gamma release assays (IGRA) in children. Although recommended for screening for latent tuberculosis infection (LTBI), many clinicians wish to employ IGRA as a diagnostic test for active tuberculosis (TB).

To compare the performance of the two commercially available IGRA and tuberculin skin test (TST) side-by-side in children with active TB and LTBI.

Prospective study of 209 children investigated for active (n=91) or latent tuberculosis (n=118). We simultaneously used TST, Quantiferon-Gold–in tube (QFG-IT) and T-Spot.TB assays.

For culture- confirmed active TB, the sensitivity of the TST was 83%, compared to 80% for QFG-IT and 58% for T-Spot.TB. IGRA did not perform significantly better than TST, although QFG-IT was significantly better than T-Spot.TB (p=0.012). The agreement between QFG-IT and T-Spot.TB in culture-confirmed TB was poor at 66.7% ( 0.15).

In LTBI, the agreement between QFG-IT and T-Spot.TB was very good (92%, 0.82) with moderate agreement between TST and T-Spot.TB (75%, 0.49, ) and QFG-IT and TST (77%, 0.53).

A negative IGRA should not dissuade paediatricians from diagnosing and treating presumed active TB. If used for diagnosis of LTBI, IGRA could significantly reduce the numbers of children receiving chemoprophylaxis with very good concordance between both tests.

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