Evaluation of polyethylene glycol precipitation as screening test for macroprolactinemia using Architect immunoanalyser

Abstract

We performed the polyethylene glycol (PEG) precipitation test to determine the prevalence of macroprolactinemia in 172 hyperprolactinemic subjects with prolactin (PRL) levels > 700 mIU/l. PRL was measured by Architect i2000 (Abbott Diagnostics) both in serum and in supernatant obtained after PEG. We used the PRL recovery percentage ( R%) as interpretative criterion of PEG test and we estimated a prevalence of macroprolactinemia of 21.5% ( R% ≤ 40%), whereas 74.4% of subjects showed a true hyperprolactinemia ( R% ≥ 60%). In true hyperprolactinemic subjects PRL levels obtained before and after PEG showed a good correlation (Pearson coefficient, R = 0.995); in macroprolactinemic individuals no correlation was found. The PEG test was also performed in 50 normoprolactinemic subjects and a new PRL reference interval was obtained: 64–453 mIU/l. In this case the macroprolactinemic subjects (hyperprolactinemic presenting a normal PRL value after PEG) were 20.3% whereas 79.7% showed still elevated PRL levels. In 35 females we were also able to evaluate the symptoms and the pituitary imaging findings: no significant differences between macroprolactinemic ( N = 11) and true hyperprolactinemic ( N = 24) subjects were found. In conclusion, the PEG test appears to be simple, reproducible and absolutely necessary for diagnostics of hyperprolactinemia.