Prevalence of Macroprolactinaemia in Women with Hyperprolactinaemia: A Retrospective Study

Introduction: Macroprolactinaemia causes asymptomatic hyperprolactinaemia in many patients which leads to misdiagnosis, inappropriate investigation and needless treatment in these patients. Though immunoassays for prolactin are sturdy and reliable, they are prone to interference from macroprolactin. Polyethylene Glycol (PEG) precipitation is used as a screening test for macroprolactinaemia. Aim: To find out the prevalence of macroprolactin in women with hyperprolactinaemia this will help in evaluation and treatment of such patients. Materials and Methods: This retrospective study was conducted at a Global Reference Laboratory in Mumbai over a period of three and a half years from January 2018 to May 2021. Total available data of 1,15,149 women with age above 18 years were included in the study. Prolactin concentrations were measured before and after PEG precipitation. Macroprolactinaemia was characterised by percentage recovery and post PEG prolactin concentrations. Continuous variables were expressed as Mean +/- Standard Deviation (SD), Range and categorical variables as number and percentage. The differences in categorical variables were assessed with Chi-square test or Fisher's-exact test. Results: A total of 36,247 women (31.48%) women out of the total 1,15,149 were observed to have hyperprolactinaemia Prevalence of macroprolactinaemia using recovery criteria of <= 50% was 7.88%. Amongst the women diagnosed with hyperprolactinaemia highest prevalence of 62.46% (22,639) was found between 18-30 years. Macroprolactin results and age were found to be statistically significant. Infertility, Oligomenorrhoea/amenorrhoea, and thyroid disorders was seen more frequently in hyperprolactinaemia than in macroprolactinaemia. Twelve women with prolactin values above 100 ng/mL were found to have macroprolactinaemia. Conclusion: Macroprolactin determination with the PEG precipitation method might prevent unnecessary tests and treatments during the diagnosis process and follow-up of patients.