Variation of immunoglobulin G and total protein concentrations during lumbar cerebrospinal fluid collection

In successive lumbar samples of cerebrospinal fluid (CSF), each consisting of 5 ml, immunoglobulin G (IgG) and total protein were determined. Variation was studied by comparing the values in the initial sample with values in succeeding samples. In 13 out of 17 patients, IgG was reduced in sample 2. There was no reduction in the following samples. The concentration of IgG in sample 2 was below 50% of the concentration in sample 1 in 2 patients and below 70% in 9 patients. IgG was also reduced if the concentration in each sample was given as percent of the total protein concentration. The total protein concentration was not significantly reduced during collection of 25 ml of CSF. IgG was increased in sample 2 in 3 out of the 4 patients with neurological diseases since childhood. In 1 patient there was a considerable rise in the total protein concentration after collection of the first 5 ml, without a corresponding rise of IgG concentration. In clinical practice, the portion to which the CSF sample belongs should be noted, and comparison of values from various patients should be made between equivalent samples.