Serum immunoglobulins: methods for the determination of normal values in international units

This paper describes the proper statistical methods for the determination of the range of normal values of serum immunoglobulins in any population and for the conversion of those ranges, or any serum immunoglobulin value, from mg per ml to World Health Organization International Units. In determining the normal range, it is argued that the analysis should be based upon the logarithms of the serum immunoglobulin values and that the range of normal values about the mean should be determined by the application of tolerance limits, rather than the more familar but incorrect confidence limits. For converting normal ranges from mg per ml to International Units, methods of parallel line bioassay (for IgG and IgA) and non-linear bioassay (for IgM and IgD) are used. For both bioassay methods, graphical techniques are described.