Assessment of macroprolactinemia by polyethylene glycol precipitation method

Abstract

BackgroundMacroprolactin is a molecule that results from association between monomeric prolactin (PRL) and immunoglobulin G (IgG). It has longer half-life and is considered biologically inactive, although it retains immunoreactivity, being detected in most available immunoassays. ObjectiveTo evaluate polyethylene glycol (PEG) precipitation method in routine detection of macroprolactin. MethodsDuring 4 months a prospective study was performed in our hospital. Serum samples of PRL≥30ng/ml were collected and pre-treated with PEG. Initial PRL and post-PEG PRL (in the supernatant) were detected by electrochemiluminescence – Cobas e170®. Samples were classified as having a predominance of macroprolactin if recovery rate (RR) of PRL was <40% and an indeterminate result for the predominance of macroprolactin if RR was 40–65%. ResultsNinety-six samples were enrolled, with median PRL 56.1ng/ml (30.7–3667). PEG precipitation produced a decrease in PRL values in all of the cases (mean reduction of 22%). Two cases of macroprolactin predominance were detected (RR 4.9% and 16.1%) and 2 cases were indeterminate (RR 45.1% and 63.7%). DiscussionPEG precipitation method is a simple and low-cost laboratory technique that can be routinely used in clinical practice. Macroprolactin accounting for hyperprolactinemia is a common cause of misdiagnosis. Screening for macroprolactin in hyperprolactinemic patients may avoid unnecessary investigation and inappropriate treatment.