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To the Editor:—
There is an omission in the interesting article in The Journal, May 14, page 129, by Stein and Hetherington, "Fifteen Years' Experience with the Tuberculin Test." This article reviews the history of the improvement of this test, its modification by the use of purified protein derivative (PPD), and the standardization of both "old tuberculin" ( OT ) and PPD for use in man. The authors cite the method of Lewis and Aronson (Am. Rev. Tuberc. 7:404 [Aug.] 1923), whereby equal amounts of a standard and an unknown tuberculin are injected intradermally and the size of the reactions compared, and state that "It is this method, modified for human subjects, that is now used to compare the potency of newly made tuberculin with a standard-strength tuberculin."This statement may have been sufficient some years ago, but since 1947 the National Institutes of Health have required all OT or PPD that
Edsall G. TUBERCULIN TEST. JAMA. 1960;173(16):1859. doi:10.1001/jama.1960.03020340077025