Optimizing laboratory defined macroprolactin algorithm

Area of Science:

• Clinical Chemistry
• Endocrinology
• Laboratory Diagnostics

Background:

• Macroprolactinaemia is a common analytical interference in hyperprolactinaemia diagnostics.
• Current methods for macroprolactin detection lack standardization, leading to inconsistent results.
• Polyethylene glycol (PEG) precipitation is a standard method for macroprolactin detection.

Purpose of the Study:

• To evaluate an in-house algorithm for macroprolactin detection and reporting.
• To determine the optimal method for reporting results after PEG precipitation.
• To assess the feasibility of rationalizing the PEG precipitation procedure.

Main Methods:

• Retrospective analysis of 1136 patient samples.
• Prolactin measurement before and after PEG precipitation using Roche cobas e601.
• Definition of macroprolactinaemia based on percentage recovery and post-PEG prolactin levels.

Main Results:

• Prevalence of macroprolactinaemia varied from 3.3% to 8.8% depending on the criteria used.
• Post-PEG prolactin concentrations alone could miss over half of macroprolactinaemic cases.
• Adjusting cut-off values showed limited impact on macroprolactinaemia detection rates.

Conclusions:

• Reporting post-PEG prolactin concentrations with a relevant reference interval is the most appropriate method.
• Samples with prolactin above the upper limit of normal require PEG precipitation.
• Follow-up measurements showed clinically insignificant differences, suggesting prolonged intervals are acceptable.