Reference ranges for serum total and monomeric prolactin for the current generation Abbott Architect assay.

BACKGROUND

Exclusion of macroprolactinaemia, a well-recognised interference, as the cause of hyperprolactinaemia is essential to avoid potential misdiagnosis and mismanagement of patients. We have derived gender-specific serum total and post-polyethylene glycol (PEG) precipitation monomeric reference ranges for the recently re-standardised Abbott Architect prolactin assay.

METHODS

Prolactin was measured in serum samples obtained from males (n=49) and females (n=52) using the current Abbott Architect immunoassay pre- and post-PEG precipitation. Gender-specific reference ranges were derived for total and monomeric (post-PEG) prolactin. Routine patients' samples (n=175) with a serum total prolactin >700 mIU/L were screened for macroprolactinaemia to assess classification compared with our previous post-PEG precipitation percentage recovery-based approach.

RESULTS

Reference ranges for serum total prolactin were 58-419 mIU/L (male) and 63-561 mIU/L (female). Male and female monomeric prolactin reference ranges were 32-309 mIU/L and 39-422 mIU/L, respectively. Mean (SD) post-PEG percentage recovery of the IS 84/500 prolactin standard was 80 (2.3)%. Of 175 patients' samples screened for macroprolactinaemia, 149 had monomeric prolactin concentrations (median monomeric prolactin=1035 mIU/L; median recovery=83%) above the gender-specific reference range. Monomeric prolactin concentrations (median monomeric prolactin=162 mIU/L; median recovery=20%) in the remaining 26 were within the reference ranges. One patient classified as macroprolactin positive and another classified as macroprolactin negative would not have been identified as such using the previous recovery-based approach.

CONCLUSIONS

The use of post-PEG monomeric reference ranges not only identifies hyperprolactinaemia due solely to macroprolactinaemia but has the added advantage of identifying patients who have simultaneous true monomeric hyperprolactinaemia and elevated concentrations of macroprolactin.