Final recommendations for macroprolactin

Abstract

Macroprolactin, a prolactin-immunoglobulin complex, continues to be a problem for prolactin measurement. It is detected by all prolactin immunoassays leading to falsely elevated prolactin levels. The current recommended best practice is to screen all samples with a high prolactin level using PEG precipitation to estimate the biologically active prolactin level. While many labs test for macroprolactin the results from a number of surveys indicate that there is variability in every step of the procedure. The AACB Macroprolactin Harmonisation Group has been formed to investigate harmonisation of the total procedure. The aim is to obtain consistency in the laboratory practice and clinical interpretation of the biologically active prolactin level across all assays and laboratories. The following are being investigated: prolactin level for screening, the technical aspects of the PEG procedure, reporting format and reference intervals. Following investigation of various steps in the PEG procedure NSW Health Pathology has established a standardised protocol which is currently being trialled. A novel method for determining the post PEG reference interval and reporting has been proposed. Additionally, the option to report monomeric prolactin post-PEG precipitation has now been included in the RCPA QAP Endocrine Program which facilitates monitoring the progress of harmonisation.