Establishment of Sex-Specific Reference Intervals for Total and Post-PEG Prolactin on an Automated Analyzer
Jessica Miller, Jason Leung, Pow Lee Cheng, Xiao Yan Wang, Maria Bhandari, Sophie Furlow, Tobias Fischer, Anselmo Fabros, Vathany KulasingamAbstract
Background
The detection of macroprolactin with common prolactin immunoassays complicates the clinical diagnosis of true hyperprolactinemia, thereby causing clinical confusion. We aimed to establish sex-specific reference intervals (RIs) for total and post-polyethylene glycol (PEG) prolactin on the Abbott Alinity i Prolactin Assay.
Methods
Total prolactin was measured in serum samples from 121 males and 126 females using the current Abbott Alinity i prolactin assay pre- and post-PEG precipitation. Reference intervals were established using R.
Results
The RIs for total prolactin was 72.3 to 634.0 mIU/L (3.4 to 29.8 ug/L) for males and 68.1 to 791.5 mIU/L (3.2 to 37.2 ug/L) in females. The post-PEG prolactin RIs established were 46.8 to 361.7 mIU/L (2.2 to 17.0 ug/L) in males and 40.4 to 517.0 mIU/L (1.9 to 24.3 ug/L) in females. The upper limit of these RIs are 75% and 53% lower than total prolactin RIs for males and females respectively, depicting precipitation of a macroprolactin and/or a mixture of dimeric and macroprolactin by PEG.
Conclusions
The current convention in macroprolactin reporting is to report the results as a percentage of prolactin recovered post-PEG precipitation compared to total prolactin, with a typical cutoff of <40% recovery to indicate positivity for macroprolactin. These findings support the potential use of assay-specific post-PEG reference intervals as a quantitative complement to percentage recovery reporting and may help to identify patients with elevated post-PEG prolactin concentrations who warrant further clinical evaluation.