Usefulness of Mantoux Test in BCG-Vaccinated Children without a BCG Scar

Bacille Calmette Guerin (BCG) vaccination is an important tool for the prevention of tuberculosis especially in highly endemic countries like Nigeria. The BCG scar which develops following BCG immunization is regarded as evidence of successful vaccination. Thus, when a child fails to develop a scar there are concerns that the immunization may not have been successful. BCG scars have recently become important because of their association with improved child survival. Tuberculin sensitivity has been used as a surrogate for successful response to BCG vaccination. The aim of this study was to find out what proportion of children with scar failure is tuberculin positive.

A prospective audit of children who presented between January and December 2016 for Tuberculin skin testing (TST) because of failure to develop BCG scar was carried out. TST was carried out by intradermal injection of 0.1ml of Purified Protein Derivative into the volar aspect of the left forearm. The size of reactions was measured 72 hours later.

Of 279 requests for TST among children aged less than 15 years, 32(11.5%) were because of BCG scar failure. There were 14 (43.8%) males and majority of the children, 22 (68.8%) were aged between 6 and 12 months. Majority, 19 (61.3%) had negative test reading (£4mm). Indeterminate values of 5-9mm were seen in 10 (32.3%) while 2 (6.5%) had positive results (³10mm) Conclusion: TSTof children without BCG scars may be useful in identifying presumptive cases of tuberculosis and children who may require prophylaxis.