Comparison of urinary free beta (hCG) and beta-core (hCG) in prenatal screening for chromosomal abnormalities

To evaluate the potential utility of free beta (hCG) and beta‐core (hCG) in a prenatal screening protocol for Down syndrome we analysed these markers in dried maternal urine specimens from 163 control, 13 Down syndrome and 5 trisomy 18 pregnancies from 8 to 25 weeks' gestation. All results are reported after normalization for urinary creatinine determined by modified Jaffe reagent assay. The correlation of urinary free beta (hCG) and urinary beta‐core (hCG) was 0·61 in controls and 0·93 in Down syndrome. Median MoM values in Down syndrome were 2·42 for urinary free beta (hCG) and 2·40 for beta‐core (hCG). In trisomy 18 the median MoM was 0·35 and 0·34 for free beta (hCG) and beta‐core (hCG), respectively. The degree of elevation observed in DS cases with urinary free beta (hCG) is consistent with previous reports. Studies of beta‐core (hCG) in Down syndrome have yielded discrepant results. In this study, beta‐core (hCG) in Down syndrome is lower than values observed in early reports but consistent with more recent reports. © 1998 John Wiley & Sons, Ltd.