DIAGNOSTIC ACCURACY OF SERUM PROTEINBOUND IODINE DETERMINATION IN THYROID DISEASE*

Abstract

IT IS generally acknowledged that the determination of the value for protein-bound iodine (PBI) in blood serum provides in most circumstances a direct quantitative estimation of the level of circulating thyroid hormone. The practical usefulness of the measurement of serum protein-bound iodine was recognized soon after the technical difficulties with regard to its accurate determination had been overcome. Unfortunately, as is often the case with a new diagnostic test, protein-bound iodine was promptly put to clinical use despite a comparative paucity of well-documented experience describing the extent of its variation in health and disease or the diagnostic precision with which it can be applied to clinical problems. Numerous papers on this subject have appeared previously (1–14). In many instances, however, conclusions have been drawn from the study of patients in whom the level of thyroid function was not fully characterized on the basis of data independent of the protein-bound iodine. The present study was undertaken because there appeared to be a need for more precise definition of the clinical potentialities of protein-bound iodine.