The two tuberculin surveys in children in Tanzania and Djibouti show two extremes of distributions that might be observed.  Children reacting with zero millimeter induration were exlcuded from graphic display.

Both surveys were conducted by professional teams using the same technique and tuberculin (intradermal application of 2 TU PPD-RT23 in 0.1 mL liquid, measuring the transverse diameter of induration after 48 to 72 hours).

In Tanzania, the expected distribution with a mode at 16 to 17 mm cannot be seen.  The largest number of reactors has an 8 mm induration.

In Djibouti, a distribution remarkably similar to that found in tuberculosis patients is seen.  The largest number of reactors has a 17 mm induration.   In contrast to Tanzania, there are only very few reactors with indurations of 5 to 10 mm.

In Djibouti, even a cutoff-point of 2 and more millimeters to denote tuberculous infection would not carry a great error in the estimation of the prevalence of tuberculous infection.  In contrast, in Tanzania, any cut-off point would either exclude children with or include children without tuberculous infection to an unpredictable extent.

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