MACROPROLACTINAEMIA - CONTRIBUTION TO HYPERPROLACTINEMIA IN A DISTRICT GENERAL-HOSPITAL AND EVALUATION OF A SCREENING-TEST BASED ON PRECIPITATION WITH POLYETHYLENE-GLYCOL

For a period of 12 months all samples submitted for serum prolactin (P RL) assay and with PRL > 700 mU/L were examined by gel filtration chro matography. In 17 (25%) of 69 samples we found macroprolactin. The Del fia and Immuno 1 immunoassay systems gave similar PRL results with sam ples containing macroprolactin whereas the ACS 180 system gave lower r esults. With the Delfia and Immune 1 systems samples containing substa ntial quantities of macroprolactin showed low recovery of PRL after pr ecipitation with polyethylene glycol 6000 (PEG 6000) and this techniqu e can be used as a screening test for macroprolactinaemia. We conclude that macroprolactinaemia is a common phenomenon and, in assays which detect this species, is a common cause of hyperprolactinaemia. Macropr olactinaemia may contribute to the difficulty in establishing an upper limit of the reference range for serum PRL. In our experience, patien ts with macroprolactinaemia do not exhibit features of the hyperprolac tinaemia syndrome and it is important to recognize macroprolactin as t he cause of hyperprolactinaemia to avoid unnecessary investigation and treatment.