IMPROVED FORMULAS FOR THE JUDGMENT OF INTRATHECALLY PRODUCED IGA AND IGM IN THE PRESENCE OF BLOOD CSF BARRIER DAMAGE

In order to discriminate between transsudated and intrathecally produc ed IgA and IgM in patients with blood cerebrospinal fluid (CSF) barrie r (BCB) damage, we developed extended indices (IgA-EI and IgM-EI) for these immunoglobulins according to the general formula for extended in dex of a component X in CSF: X-EI = (CSF-X/serum-X)/(CSF-albumin/serum -albumin)a where a is a parameter specific for X. For IgA parameter a was found to be 1.15 and for IgM 1.9. A preliminary evaluation of IgA- EI and IgM-EI indicated lower false positive rates as compared to CSF IgA and IgM concentrations as well as 'conventional' IgA and IgM indic es in cases with BCB damage, and essentially the same rates as for the hyperbolic formulae of Reiber and Felgenhauer. The importance of reli able sampling and analytical technique for IgM in CSF is discussed.