Objective:Interferon gamma (IFNg) based assays are an exciting new development when screening for latent tuberculosis infection (LTBI) in adults, but there are limited data in children. Nevertheless new NICE guidelines recommend their use when screening paediatric Tuberculosis (TB)contacts. We evaluated the potential impact of new NICE guidelines on current paediatric practice.
Design:Children screened for tuberculosis (TB) who had an IFNg assay (QuantiFERON-TB Gold [QFG]) were included. Actual outcomes from existing guidelines were compared to those that would have been obtained using NICE guidelines.
Results:QFG assays were performed on 120 children, 103 as part of TB contact tracing. 6/120 (5%) were QFG positive, and 7/120 (6%) indeterminate. Where both Mantoux and QFG results were available these agreed in 62/104 (60%). QFG tests were more likely to correlate with a negative Mantoux (98% agreement) than with a positive Mantoux (11% agreement). Management outcomes differed for 23/103 seen as part of TB contact tracing. Only 1(1%) of these had an indeterminate QFG result. Seventeen (85%) fewer children would have been given LTBI treatment (chemoprophlaxis) and two (2 %) children exposed to TB with chest x-rays suggesting TB would not have been identified using NICE guidelines.
Conclusion:New NICE guidelines for the use of IFNg based tests in TB screening will decrease the number of children treated for presumed LTBI. Long term prospective studies are needed to determine the number of children with positive Mantoux tests but negative IFNg results who are not given LTBI treatment yet later develop TB disease.
- contact tracing
- interferon gamma test
- latent tuberculosis
- tuberculin skin test