THE RELATION of tuberculin sensitivity to pulmonary calcifications as an index of tuberculosis infection.

A single intradermal tuberculin test of 10 TU was arbitrarily selected for use in the Danish mass antituberculosis campaign of 1950-52. The present report discusses how efficiently this test can distinguish tuberculosis-infected and uninfected members of the adult population; it is based on the relation between size of tuberculin reaction and frequency of intrathoracic (presumably tuberculous) calcifications in 50,000 adults.Frequency distributions by size of 10 TU reactions for the study population, divided into 10-year age-groups, show a very consistent pattern for all age-groups: a smooth bimodal curve with a zone of low frequency around the 6 mm point of induration clearly separating persons with large reactions from those with very small or no reactions.In persons 15-34 years old the frequency of pulmonary calcifications is very low for those with tuberculin reactions measuring 0-7 mm of induration; for those with reactions of 8-9 mm the frequency rises sharply and reaches a maximum for those with reactions 18 mm or larger. In the age-groups up to 54 years the frequency of calcifications remains very low in persons with no reactions to the tuberculin test; the sudden steep rise in frequency is displaced with age from right to left on the tuberculin-reaction scale, and there is a progressive increase in the frequency of calcifications with the increase in reaction size. In the age-group 55 years or more persons with no reaction also have a high frequency of calcifications, and there is only a very slight rise in the frequency from 0-1 mm to the largest reactions.Up to the age of about 50 years, probably few persons not reacting to the 10 TU test are tuberculosis-infected. For persons over this age, however, division of the population into two groups according to the tuberculin-reaction size apparently does not correspond to a division into infected and uninfected.