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To the Editor:—
In regard to the answer of Dr. J. H. Lewis to the question "Blood in Feces" (JAMA178:534 [Nov. 4] 1961), I would like to make 2 statements. One concerns the sensitivity of the benzidine test: A long time has elapsed since O. and R. Adler's original article and the Schlesinger-Holst modification about using benzidine to determine occult blood in the stool. The very sensitive method was modified in 1919 by J. P. Gregersen to reduce its sensitivity. Today, methods of reduced sensitivity using benzidine di-hydrochloride exist. I have found equal sensitivity between this improved benzidine di-hydrochloride and the guaiac methods. Meat-free diet is not a "must" with the benzidine method mentioned. The second statement concerns the so-called better "specificity" of guaiac. I do not know in what way this word is used. If used literally, it would be the same as stating that the V.D.R.L.
dos Santos JG. Tests for Blood in Feces. JAMA. 1962;179(5):386. doi:10.1001/jama.1962.03050050076021
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