[Comparative study of biological case findings made with 1 and with 2 units of PPD]

Testings were carried out with one unit of PPD in 2865 children aged between 1 and 6 years in the course of 1972 and with two units of PPD in 2822 children aged between 1 and 6 years in the course of 1973. The aspect of the histograms of the two groups was clearly different, the one corresponding to 2 units, tested children showing a more marked bi-modal aspect due to the higher number of reactions of 10-11 mm in diameter (7,5%). The data resulting from the processing of the histograms, of the infecting density of the environment and of the median diameters of the reactions were not conclusive. Between the children tested with one unit 6 cases were detected (5 of which with active tuberculosis), while between those tested with 2 units 22 cases were found (one of wich with an active form of tuberculosis). Among the children tested with one unit of PPD contamination sources could be detected in 100% of the cases and in those tested with 2 units in 51,2% of the cases. The methodology based on the exclusive examination of hyperallergics to one unit of PPD and of their contacts, as compared with the examination of all positive reactions to 2 units and of their contacts has a resolution ability which is higher for an amount of work roughly 30 times less, but in the detection campaign it may omit sick children and contaminators that have not been known until the investigation. The author suggests for the examination of all positive cases with reactions to 2 units of PPD and of their contacts.