Post-polyethylene glycol (PEG) treated prolactin levels for the detection of macroprolactin - time to change

Objective: It has been shown that macroprolactin (MaPRL) is biologically inactive because the large molecular size of this complex prevents its crossing through the capillary blood barrier and reaching target cells. The aim of this study is to detect the frequency of MaPRL in hyperprolactinaemic patients by using PEG precipitation method and to report the post-PEG treated results in order to facilitate interpretation of the result, provide more clinically useful information, and enhance patient care. Material and Methods: A prospective study was conducted at the Section of Chemical Pathology, Department of Pathology and Microbiology Aga Khan University (AKU) between 5th to 20th Oct 2013. During this period total 280 patients were tested for serum prolactin levels. From this subset of 40 subjects with high prolactin levels i.e. from 25-150 ng/ml in females and 15-150 ng/ml in males were selected for PEG precipitation. PEG precipitation was performed by PEG 8000 and results were interpreted by using post PEG treated reference range of Males 3.6–12.4 ng/ml and Females 4–18.5 ng/ml. Data was analyzed by SPSS version 19. Results: Sera from 40 patients with elevated serum PRL concentrations were screened for macroprolactinaemia by PEG. Out of which 38 were females (92.7 %) and 3 were males (7.3%). Serum prolactin levels became normal after post PEG treatment in 15 individuals (36.6 %) suggestive of macroprolactin while it remained elevated in 26 (63.4%) demonstrating true hyperprolactinemia. Conclusions: A significant number of subjects are found to have high serum prolactin levels due to MaPRL, which is a significant cause of misdiagnosis, unnecessary investigation, and inappropriate treatment. We recommend treatment of high prolactin results with PEG for accurate results and enhancing quality of care to the patients. Keywords: Polyethylene glycol (PEG), Macroprolactin, Macroprolactinaemia, Hyperprolactinaemi