Rapid manual immunoturbidimetric and immunonephelometric assays of prealbumin, albumin, IgG, IgA and IgM in cerebrospinal fluid.

Manual turbidimetric kinetic assays (10 to 20 samples/h) for the determination of prealbumin, albumin, IgG and IgA in CSF, and a turbidimetric end point assay for IgM are described for a mechanized microliter system (Eppendorf); it uses microcuvettes (total volume 300 microliter) and polyethylene glycol to increase sensitivity (detection limit 1 to 3 mg/l) and reaction velocity (less than or equal to 12 min and 25 min, respectively). The results correlated satisfactorily with those obtained with laser end point nephelometry (1-2 h, total volume with Hyland laser 750 microliter, with Behring laser 225 microliter), e.g. correlation coefficient of greater than 0.9 for comparison of CSF samples, recovery rates approximately 90 to 110%, day to day precision less than 10%. No interference with other proteins was observed (e.g. hemoglobin). The turbidimetric assays were generally less expensive with respect to reagents (by factor 2 to 20), and they required smaller sample volumes (by factor 2) and less technician time (by factor 2 to 4, especially for number of samples less than or equal to 10) than both nephelometric end point assays, because they do not need daily established calibration curves. The turbidimetric kinetic assay in series to 6 samples can be compared to the Beckman immunochemistry analyser which requires still less time, but is less sensitive and more cost-intensive.