Detection of molecular variants of prolactin in human serum, evaluation of a method based on ultrafiltration.
BACKGROUND
In human blood, there are several molecular variants of prolactin with different biological effects. There is a need for new methods to detect and quantify these variants in order to fully understand the pathophysiological role of prolactin.


METHODS
A method based on ultrafiltration was optimized, validated and compared to PEG precipitation. Serum samples from 84 patients were analyzed before and after pre treatment on two immunoassays, Elecsys (Roche) and Access (Beckman). Protein G precipitation was used to confirm presence of macroprolactin.


RESULTS
The recovery of prolactin after ultrafiltration was lower than after PEG precipitation. A limit of 40% recovery after PEG precipitation corresponded to 27% recovery after ultrafiltration. Using these limits there were total agreement regarding detection of macroprolactin (r(s)=0.96). In contrast, recovery of prolactin in samples without macroprolactin showed a considerable disagreement between ultrafiltration and PEG precipitation (r(s)=0.48). Within-run CV was 4% for the ultrafiltration method. The correlation coefficient (r) between the immunoassays was 0.96 after ultrafiltration.


CONCLUSIONS
Ultrafiltration can be used to compare different prolactin immunoassays and to detect macroprolactin in assays with interference from PEG. For samples without macroprolactin ultrafiltration may give additional information reflecting individual variations of other molecular variants of prolactin.
Landberg
Eva
E
Division of Clinical Chemistry, Department of Biomedicine and Surgery, Linköping University Hospital, S-581 85 Linköping, Sweden. eva.landberg@lio.se
Wahlberg
Jeanette
J
Rydén
Ingvar
I
Arvidsson
Britt-Mari
BM
Ekman
Bertil
B
D000293:Adolescent; D000328:Adult; D000368:Aged; D011232:Chemical Precipitation; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011092:Polyethylene Glycols / Q000737:chemistry; D011388:Prolactin / Q000097:blood* / Q000302:isolation & purification; D014462:Ultrafiltration / Q000379:methods
C060678:prolactin, polymeric; D011092:Polyethylene Glycols; D011388:Prolactin