Detection of macroprolactinemia in hyperprolactinemic patients by PEG precipitation using Elecsys 2010 immunoanalyser

Objective: Macroprolactinemia is one of the important and benign causes of hyperprolactinemia. Recognition of this benign condition can avoid unnecessary diagnostic procedures and inappropriate treatments. The aim of our study was to evaluate the effectiveness of polyethylene glycol (PEG) precipitation test in determining the macroprolactinemia in hyperprolactinemic subjects using Elecsys 2010 immunoanalyser.Methodology: We performed the PEG precipitation test in 188 hyperprolactinemic subjects with prolactin levels 750 mIU/L. The results of PEG test were expressed as prolactin recovery (R% value).We also performed PEG precipitation test on 100 sera from normoprolactinemic subjects for determination of PEG precipitation test reference interval.Results: According to the recovery percentage (R%) interpretative criterion, the prevalence of macroprolactinemia was 17% (R% 40%), whereas 80.8% of subjects showed a true hyperprolactinemia (R% 60%). We also estimated the prevalence of macroprolactinemia by comparing the PEG test results with PEG test reference interval. By this new interpretative method, the prevalence of macroprolactinemia was 18.6%, while 81.4% showed true hyperprolactinemia.Conclusion: We recommend PEG precipitation test as a simple, convenient and rapid screening method for macroprolactinemia, specially for users of Elecsys 2010 immunoanalysers, because this system has high reactivity to macroprolactin