It was shown elsewhere1 that the regular Kahn test with standard antigen is considerably less sensitive than the presumptive procedure which employs sensitized antigen. In the general run of cases observed in the University Hospital, the presumptive procedure is 2.5 per cent more sensitive and in patients treated for syphilis 26 per cent more sensitive than the regular test. The question arose as to the comparative sensitiveness of the quantitative Kahn procedure when the standard and sensitized antigens were employed.
It will be recalled that the quantitative procedure gives the potency of syphilitic serums in terms of Kahn units.2 One of several serums giving 4 plus reactions might indicate 800 units, another 400 and still another perhaps 120. These units are determined by the performance of the precipitation reaction with a series of serum dilutions under constant conditions. The highest dilution in which precipitation occurs establishes the number
McDERMOTT EB. THE QUANTITATIVE KAHN PROCEDURE WITH STANDARD AND SENSITIZED ANTIGENS. Arch Derm Syphilol. 1929;20(6):860–861. doi:10.1001/archderm.1929.01440060096009
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