Diagnostic usefulness of mycobacterial skin test antigens in childhood lymphadenitis

Nontuberculous mycobacterial (NTM) infections are a frequent cause of chronic lymphadenitis in children. Previous studies of NTM antigen skin testing were inconclusive as a result of problems with study design and antigen formulation. The present study was undertaken with the Centers for Disease Control to determine whether newly formulated NTM skin test antigens applied in a double blind manner with a standard purified protein derivative could accurately distinguish NTM infections from those caused by Mycobacterium tuberculosis. Among the 11 children enrolled at our institution the NTM antigens correctly identified the 5 children with culture-proved NTM infections, as well as 2 other children with clinical or histopathologic data consistent with NTM lymphadenitis (P = 0.003, Fisher test). None of the 11 children cross-reacted with the Centers for Disease Control-supplied purified protein derivative. The NTM antigens appear to be useful in the diagnostic evaluation of lymphadenitis and perhaps in the evaluation of children with positive purified protein derivative skin tests.