[Calculation of the IgG fraction of cerebrospinal fluid locally synthesized in the central nervous system (author's transl)].

The cerebrospinal fluid (CSF)/serum concentration ratios of immunoglobulin G and albumin were determined for a group of n = 334 control patients. The correlation coefficient relating the two quotients was r = 0.71. The regression line was found to be y = 0.41 x + 0.00014. For statistical and functional reasons it is plausible that the theoretical line should go through the origin. The ocrresponding function would than be y = 0.43 x. The confidence range of the IgG quotient (y) for a given albumin quotient (x) is characterised by +/- 2 Sy.x = +/- 0.001 (Sy.x is the standard deviation of the y values from the regression line). If the IgG quotient is evaluated for the individual albumin ratio of the patient, the following formula can be used for calculation of the locally synthesized concentration of pathological IgG (IgGp) in CSF: IgGp = IgG(CSF) - (0.43 Alb(Serum)-Alb(CSF) + 0.001) . IgG(Serum). This method of determination is independent of the variables which are known to influence the individe, sex, individual blood brain barrier condition, extraction volume of CSF and the method used for protein determination. In comparison with other methods, particularly with respect to the statistics and biochemistry, the reported formula allows an optimal evaluation of pathological IgG values in CSF.