[Two step tuberculin testing among elderly Japanese admitted to residential homes]

This study was carried out to know the prevalence and determinants of tuberculin reactors and the size of booster phenomenon in 211 Japanese residents of a provincial nursing home for elderly. The age of the study subjects ranged from 65 to 99 (mean 83.2), and no subjects were foreign born, and had any history of BCG vaccination. The prevalence of TB infection in this aged group was estimated 70% or higher. Testing was done according to the standard method used in Japan. Results showed that 35.1% of subjects were positive by the initial test, and 27.0% converted to positive by the second test, thus altogether 52.6% were positive by two step test. No association was found between the prevalence of tuberculin positive rate and the age or the performance status. Lower body mass index, lymphocytopenia, hypoalbuminemia and PNI (prognostic nutritional index) were seen to relate with the weakened tuberculin skin reaction.