Nicked free beta-subunit of human chorionic gonadotropin: a potential new marker for Down syndrome screening.
OBJECTIVE
Our purpose was to investigate maternal serum levels of nicked free beta-subunit in normal and Down syndrome pregnancies.


METHODS
Serum specimens were obtained from 64 karyotypically normal and 6 Down syndrome pregnancies before amniocentesis. Two immunoenzymometric assays for the beta- subunit of human chorionic gonadotropin were used to determine the level of free beta-subunits with peptide linkage breaks ("nicks") between residues 43 to 48.


RESULTS
The mean level of nicked free beta-subunit in Down syndrome was 4.76 multiples of the median, which was significantly elevated compared with normal controls (1.07 multiples of the median, p<0.05). In 5 of 6 cases levels were > or = 2 multiples of the median, with a range of 1.96 to 15.43 multiples of the median, which was 2- to 3-fold higher than the regular free beta-subunit assay (mean level 1.53 multiples of the median, range 0.70 to 3.10 multiples of the median). In one case no nicked free-beta subunits were detectable.


CONCLUSIONS
Our preliminary data indicate that nicked free beta-subunit of human chorionic gonadotropin might be a sensitive marker for Down syndrome screening.
Rotmensch
S
S
Division of Maternal-Fetal Medicine, Hasharon Hospital, Petah Tiqva, Israel.
Liberati
M
M
Kardana
A
A
Copel
J A
JA
Ben-Rafael
Z
Z
Cole
L A
LA
D015415:Biomarkers / Q000097:blood; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood*; D004314:Down Syndrome / Q000097:blood / Q000175:diagnosis*; D005260:Female; D005865:Gestational Age; D006801:Humans; D007124:Immunoenzyme Techniques; D011247:Pregnancy; D011296:Prenatal Diagnosis; D012016:Reference Values
D015415:Biomarkers; D018997:Chorionic Gonadotropin, beta Subunit, Human