Unreliability of the Mantoux test using 1 TU PPD in excluding childhood tuberculosis in Papua New Guinea.

139 children with bacteriological or histological proof of active tuberculosis were given the Mantoux tuberculin test while they were inpatients at Port Moresby General Hospital. Only half (70) of the children had positive results (induration of at least 5 mm). Of the 35 children under 2 years, 25 (71%) showed no reaction whatsoever. Malnutrition, assessed by weight for age, did not appear to influence the response although nearly all children under 5 weighed less than the Harvard mean. Previous BCG immunisation had no significant effect on the reaction to tuberculin. General debility, recent measles, treatment with corticosteroids, or early stage of illness may account for some negative reactions, but whatever the cause, the high proportion of negative results means that the tuberculin test as currently practised in Papua New Guinea cannot be relied on to exclude active tuberculosis in children.