[Laboratory findings in cerebrospinal fluid in relation to age: trivariate evaluation of albumin and immunoglobulin G concentrations (author's transl)].

In cerebrospinal fluid from controls ("non-diseased probands", n = 326) the following variables were determined: albumin and immunoglobulin G (by immunodiffusion) and total protein. Total protein rose parallel with the age of the subjects (r = 0.319); the albumin fractions (r = 0.126) and immunoglobulin G (r = 0.144) also correlated with age. The concentrations of albumin and immunoglobulin G were correlated even more closely (r = 0.589), leading to a particularly slender form of the elliptic bivariate normal range. The correlation of the variables albumin and immunoglobulin G with each other and with age was drawn upon as additional information, in order to discriminate between laboratory findings from diseased and from non-diseased subjects: a trivariate area of reference ("trivariate normal range") was calculated, which avoided errors of the second kind (diseased values not recognized) more powerfully than the usual one-dimensional ranges (x +/- 2s or percentile).