Immunoglobulin concentrations in sera of normal children: quantitation against an international reference preparation.

The quantitation of immunoglobulins in human sera is a common procedure in clinical laboratories and is useful both for clinical and research purposes. Several papers have been published on the subject. Because significant age-related changes occur before adult life, most reports deal with immunoglobulin values in normal children (1-4). However, the data from different laboratories are difficult to compare because a wide variety of immunoglobulin preparations, obtained from different sources, have been used as standards for the quantitation; thus, data expressed in mg/100 ml and based on local immunoglobulin standards are of limited use for comparative studies. With the object of improving the uniformity of immunoglobulin quantitations in different laboratories, an international reference preparation for human serum immunoglobulins has been established (5) by the WHO International Center for Immunoglobulins. It has been recommended (6) that the concentration of the individual immunoglobulins be estimated against this reference preparation and expressed in International Units (I.U.) per milliliter. Our aim was to establish normal serum immunoglobulin values from birth to adulthood, in terms of I.U./ml; this approach should help in unifying immunoglobulin quantitations on the basis of the international standard, facilitate valid comparisons between different laboratories, and lead to full appreciation of the clinical significance of immunoglobulin determinations.