The analytical specificity of human chorionic gonadotropin assays determined using WHO International Reference Reagents.
BACKGROUND
Human chorionic gonadotropin (hCG) is a heterodimeric glycoprotein hormone with considerable molecular heterogeneity. There is uncertainty regarding which hCG variants are detected by different hCG assays. The analytical specificity of 8 hCG assays was investigated.


METHODS
WHO International Reference Reagents for hCG, nicked hCG (hCGn), beta subunit (hCGbeta), nicked beta subunit (hCGbetan), and beta core fragment (hCGbetacf) were individually added to hCG-free human serum. Specimens were analyzed with 8 commercially available hCG assays. Equimolar detection of hCG variants was defined as a recovery of 90-110%.


RESULTS
All assays detected hCG and hCGn with mean recoveries of 98.3 and 94.6%, respectively. Seven assays detected hCGbeta (mean recovery 103.8%) but with high variation, and equimolar detection was observed only in four. The mean recovery of hCGbetan was 85.5% but was highly variable with only two assays showing equimolar detection. With a mean recovery of 53.4%, two assays detected hCGbetacf and both underestimated it considerably. Information provided by the assay manufacturer regarding hCG variant analytical specificity was inadequate or unclear in 75% of the assays.


CONCLUSIONS
hCG assays vary considerably in their ability to detect different hCG variants. Manufacturers of hCG assays should clearly indicate the hCG variant specificity of their reagent systems.
University of Utah Health Sciences Center, Department of Pathology, Salt Lake City, UT 84108, USA.
JoDell
J
Whittington
Corinne R
CR
Fantz
Ann M
AM
Gronowski
Christopher
C
McCudden
Richard
R
Mullins
Lori
L
Sokoll
Carmen
C
Wiley
Andy
A
Wilson
David G
DG
Grenache
D006063:Chorionic Gonadotropin / Q000032:analysis* / Q000097:blood / Q000592:standards / Q000652:urine; D006801:Humans; D007202:Indicators and Reagents / Q000737:chemistry*; D012015:Reference Standards; D015203:Reproducibility of Results; D014944:World Health Organization
D006063:Chorionic Gonadotropin; D007202:Indicators and Reagents