P175 Mantoux or gamma Interferon (IGRA)--which test is best in children?

Abstract

Introduction: NICE guidelines recommend a Mantoux threshold of15 mm induration to trigger investigation for tuberculosis (TB),with IGRA tests used as second line in selected groups. Little dataare available about the role of the two tests in the diagnosis of activeTB. Emerging evidence suggests IGRA tests may be more sensitive inidentifying TB infection in children.Aim To explore the relationship between Mantoux and IGRA inchildren attending a paediatric TB clinic in Manchester.Hypothesis A Mantoux threshold of ≥15 mm induration underestimatesTB infection in children.Method All children aged 0-17 years referred to the TB service atCentral Manchester Foundation Trust between Jan 2009 and May2011 were included. Initial screening included symptom review andMantoux testing. Based on induration at 48-72 h, Mantoux testswere defined as negative<6 mmor positive≥6 mmfor those with noprior BCG, and negative <10 mm, borderline 10 to ≥15 mm or positive ≥15 mmfor those with prior BCG. Children with borderlineor positive Mantoux test results, or in whom there was clinicalconcern, were referred for consultant assessment and/or IGRA(Quantiferon Gold). Data were collected retrospectively from casenotes. Results: 976 children were referred. 756 completed initial assessment(388 (51%) male, mean age 6.2±4.6 years, range 0.16-16.36 years).BCG history was known in 754 (99.7%; 516 BCG). 403 patientswere discharged without intervention, 63 were offered BCG vaccination,two were referred elsewhere and 288 were referred forconsultant assessment. Of these 288, 108 were notified with TB, 46received chemoprophylaxis, 117 received no treatment, 5 receivedBCG and 12 failed to attend. 252 children had paired Mantoux andIGRA. Of these, 18/44 (41%) of those with a borderline Mantouxhad a positive IGRA. 126/252 had TB infection (91 active and 35latent TB)-see Abstract P175 table 1. A Mantoux threshold of≥15 mm identified 77 (61%) children with TB infection, IGRAidentified 92 (73%) and the two tests combined identified 100 (79%)children. (Table presented) Conclusion: Using a Mantoux threshold of ≥15 mm indurationsignificantly underestimates the number of children with TBinfection compared with using Mantoux and IGRA together.