Introduction
The significance of roentgenographically
unchanging pulmonary lesions, in the absence
of bacteriologic or pathologic proof
of etiology, is difficult to determine.1 It has
been shown by Britten2,3 that many such
cases subsequently develop tuberculosis. The
problem of the diagnosis of these cases is of
special importance to the Armed Forces
where intimate environmental situations exist.
It therefore became necessary to assess
accurately the risk of such persons developing
active pulmonary tuberculosis and
thereby becoming sources of infection.
The purpose of this study was to measure
the risk among military personnel retained
on active duty after clinical study had
rendered diagnoses of "infiltration, pulmonary,
cause undetermined" or "fibrosis,
pulmonary, cause undetermined." These two
diagnoses were established in 1948 by a
Joint Armed Forces decision4 in order to
afford an orderly classification of unchanging,
predominantly noncalcified pulmonary
lesions of unknown etiology.
Material—Selection and Sources
A study group consisting of personnel with the
above diagnoses and