Distortion of PBI Determination During Coronary Care

Abstract

To the Editor. —The protein-bound iodine (PBI) determination has become the standard clinical means of thyroid evaluation. The factors known to affect its results have been summarized elsewhere. 1,2 The following report of a heretofore unrecognized cause of significant PBI distortion is the result of an investigation conducted because a disproportionate number of patients admitted to the St. Luke's Hospital intensive-care unit (ICU) were found to have elevated serum PBI levels. Over a six-month period, 50% of the PBI values of patients in the ICU were elevated above normal values, in contrast to 7.3% in the other hospital division studied. The Figure reports a study of a patient admitted to the ICU who had daily PBI determinations. This graph reveals a biphasic curve; the first peak occurred soon after the patient's admission to the ICU; the second peak corresponds to the patient's readmission to the ICU after his condition deteriorated