![]() fortuitum and PPD-Y from the yellow photochromogen M. avium PPD-G from the Gause strain of schotochromogen PPD-B from the nonphotochromogen Battey bacilli PPD-F from the rapid grower M. atypical) mycobacterium are identified by a letter other than S. The “old tuberculin” is no longer used for this purpose instead, a more standardized product called PPD-S (purified protein derivative, prepared according to the method described by Siebert, from M. The tuberculin most widely used is purified protein derivative (PPD), which is derived from cultures of M. The distribution of results generally falls into one of two patterns depending on the rate of false-positive (cross-reactions from other mycobacterial infections) in the population. Consequently, its application in any group of patients will usually yield a wide range of results, from the presence of a reaction in uninfected children to the complete absence of a reaction in some children with confirmed TB disease. However, various factors both in the host and inherent in the test lower both its specificity and sensitivity. After such a long history it is surprising that the interpretation of the test remains controversial. It was developed by Koch in 1890 but the intradermal technique currently in use was described in 1912 by Charles Mantoux, a French physician who developed on the work of Koch and Clemens von Pirquetto to create his test in 1907. tuberculosis infection in an individual and is used in the diagnosis of TB in individual patients, as well as in epidemiological settings, to measure the prevalence of tuberculous infection in populations. ![]() Short of demonstrating viable organisms in body tissues and fluids the tuberculin skin test (TST) is the only method of detecting M. ![]() A combination of factors including high costs, limited resources and the poor performance of various diagnostic tests make the diagnosis of TB difficult in developing countries. Tuberculosis (TB) remains a leading cause of morbidity and mortality in the world, especially in developing countries. ![]()
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