While there is considerable disagreement between investigators as to the exact value of the various observations with Lange's colloidal gold test for cerebrospinal fluid,1 all are unanimous in their opinion regarding its value as a useful confirmatory test in the diagnosis and the differentiation of syphilitic and nonsyphilitic diseases of the central nervous system.
The test is based on the observations of Zsigmondy2 that proteins will protect various colloidal substances from being precipitated by electrolytes. The degree of protection has been found to be specific for each protein, and is expressed in terms of milligrams of the protein that is capable of protecting 5 cc. of colloidal gold against 0.5 cc. of a 10 per cent solution of sodium chloride.
It has been known for a long time that the protein content in spinal fluid varies in pathologic conditions of the central nervous system. Accordingly, Lange took advantage of Zsigmondy's observations and endeavored to apply them to the quantitative determination of protein in the spinal fluid; however, contrary to his expectation, he found that an excess of protein precipitated colloidal gold instead of protecting it.
LEIBOFF SL. COLLOIDAL GOLDA METHOD FOR THE PREPARATION OF COLLOIDAL GOLD FOR THE LANGE TEST ON CEREBROSPINAL FLUID. Arch Derm Syphilol. 1928;17(3):380–386. doi:10.1001/archderm.1928.02380090093009