Prolactin measurement is very common in standard clinical practice. It is indicated not only in the study of
pituitary adenomas, but also when there are problems with fertility, decreased libido, or menstrual disorders, among other problems. Inadequate interpretation of
prolactin levels without contextualizing the laboratory results with the clinical, pharmacological, and gynecological/urological history of patients leads to erroneous diagnoses and, thus, to poorly based studies and treatments. Macroprolactinemia, defined as
hyperprolactinemia due to excess
macroprolactin (an
isoform of a greater molecular weight than
prolactin but with less
biological activity), is one of the main causes of such erroneous diagnoses, resulting in poor patient management when not recognized. There is no unanimous agreement as to when
macroprolactin screening is required in patients with
hyperprolactinemia. At some institutions,
macroprolactin testing by
polyethylene glycol (PEG) precipitation is routinely performed in all patients with
hyperprolactinemia, while others use a clinically based approach. There is also no consensus on how to express the results of
prolactin/
macroprolactin levels after PEG, which in some cases may lead to an erroneous interpretation of the results. The objectives of this study were: 1. To establish the strategy for
macroprolactin screening by serum precipitation with PEG in patients with
hyperprolactinemia: universal screening versus a strategy guided by the alert generated by the clinician based on the absence or presence of clinical symptoms or by the laboratory when
hyperprolactinemia is detected. 2. To create a consensus document that standardizes the reporting of
prolactin results after precipitation with PEG to minimize errors in the interpretation of the results, in line with international standards.