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Determination of ultrafilterable prolactin: elimination of macroprolactin interference with a monomeric
Adam M Quinn1, Tara C Rubinas, C Jean Garbincius
1Department of Pathology, Loyola University Medical Center, Maywood, Ill, USA. adamquinn1@gmail.com
Context:
Macroprolactin (macroPRL), present in as many as 25% of serum specimens with elevated serum prolactin concentrations, can cause apparent hyperprolactinemia in the absence of clinical features and lead to unnecessary clinical, laboratory, and neuroradiological workups.
Objective:
To develop an ultrafiltration method that eliminates macroPRL interference from PRL immunoassays.
Design:
The method involves centrifugation of undiluted serum in a Centricon-100 filter device followed by a PRL assay of the serum ultrafiltrate.
Results:
Ultrafiltrates prepared by this technique are devoid of gamma globulins and contain (mean +/- SE) 19% +/- 7% of the albumin concentration of the original serum. These ultrafiltrates contain 85% +/- 7% of the total PRL immunoreactivity of serum spiked with 23 kd recombinant human prolactin (rHuPRL) and less than 2% of the 50 kd big PRL (bPRL) of whole serum. The fractional recovery of ultrafilterable PRL (uPRL) from serum samples of 54 female patients was 0.78 (confidence interval 0.73-0.83) of the total. The run-to-run coefficient of variation of the uPRL assay was 4.3%. The uPRL concentration (mean +/- SD) in a group of healthy female controls was 8.0 +/- 3.1 ng/mL.
Conclusions:
Ultrafiltration is a rapid and simple method for eliminating analytical interference by macroPRL. Ultrafiltrates can be analyzed by most, if not all, currently available PRL immunoassays and represent a practical and precise alternative to gel filtration chromatography for the estimation of the monomeric prolactin concentration of serum.
Insights
Ultrafiltration effectively removes macroprolactin (macroPRL) interference in prolactin (PRL) immunoassays. This method provides a practical alternative for accurately measuring monomeric PRL levels.
Area of Science:
- Clinical Chemistry
- Endocrinology
- Laboratory Medicine
Background:
- Macroprolactin (macroPRL) causes apparent hyperprolactinemia in up to 25% of elevated prolactin tests.
- This can lead to unnecessary clinical investigations and diagnostic procedures.
Purpose of the Study:
- To develop an ultrafiltration method to eliminate macroPRL interference in prolactin (PRL) immunoassays.
- To establish a practical and precise method for measuring monomeric PRL.
Main Methods:
- Serum ultrafiltration using a Centricon-100 filter device.
- Assay of prolactin (PRL) in the serum ultrafiltrate.
Main Results:
- Ultrafiltrates removed macroPRL, retaining 85% of total PRL immunoreactivity.
- Fractional recovery of ultrafilterable PRL (uPRL) was 0.78.
- The uPRL concentration in healthy females was 8.0 +/- 3.1 ng/mL.
Conclusions:
- Ultrafiltration is a rapid, simple method to eliminate macroPRL analytical interference.
- Ultrafiltrates are suitable for most PRL immunoassays.
- This method is a practical alternative to gel filtration chromatography for monomeric PRL estimation.
