An international reference preparation for human serum immunoglobulins G, A and M: content of immunoglobulins by weight.

An International Reference Preparation for Human Serum Immunoglobulins G, A, and M has been established by the World Health Organization and international units have been assigned to it. This paper describes international collaborative assays carried out by 10 specialized laboratories, which attempted to define the immunoglobulin contents of the International Reference Preparation by weight. For all immunoglobulins the estimates of contents by weight were imprecise, largely owing to heterogeneity of estimates between laboratories. Mean estimates of immunoglobulin contents by weight are given, but it is considered that the results of assays of immunoglobulin against the International Reference Preparation or related preparations are more precisely expressed in terms of international units.