Maternal weight correction of maternal serum PAPP-A and free β-hCG MoM when screening for trisomy 21 in the first trimester of pregnancy
Article first published online: 10 SEP 2003
Copyright © 2003 John Wiley & Sons, Ltd.
Volume 23, Issue 10, pages 851–855, October 2003
How to Cite
Spencer, K., Bindra, R. and Nicolaides, K. H. (2003), Maternal weight correction of maternal serum PAPP-A and free β-hCG MoM when screening for trisomy 21 in the first trimester of pregnancy. Prenat. Diagn., 23: 851–855. doi: 10.1002/pd.708
- Issue published online: 10 SEP 2003
- Article first published online: 10 SEP 2003
- Manuscript Accepted: 21 JUL 2003
- Manuscript Revised: 16 JUL 2003
- Manuscript Received: 10 APR 2003
- Down syndrome;
- prenatal screening
To assess the suitability of either the log-linear or reciprocal-linear regression procedure for maternal weight correction of biochemical marker MoMs in the first trimester.
Data from two prospective first-trimester OSCAR screening programmes including 32 010 women with first-trimester maternal serum-free β-hCG and PAPP-A measured by the Kryptor analyser was analysed by regression analysis to provide parameters for the log-linear and reciprocal-linear MoM correction procedures. Assessment was made by goodness of fit to the data. The impact on detection rate and false-positive rate of the different correction procedures was assessed using statistical modelling with biochemical markers alone.
Both log-linear and reciprocal-linear correction were shown to fit the data well. For free β-hCG, the log-linear procedure was marginally superior to the reciprocal-linear procedure (r2 = 0.986 v 0.980), whilst for PAPP-A the reciprocal-linear procedure was marginally better (r2 = 0.991 v 0.985). Log-linear correction reduced the variance for both markers more than did the reciprocal-linear procedure. For free β-hCG, the sd was reduced from 0.2675 to 0.2605 and for PAPP-A, it was reduced from 0.2545 to 0.2336. Correcting for maternal weight was shown to reduce the population false-positive rate from 7.0 to 6.5%, whilst maintaining the same detection rate at a risk cut-off of 1 in a 100. At individual levels, a two-fold variation in risk was demonstrated depending upon the individual's weight.
To provide accurate individual patient-specific risks for trisomy 21, maternal weight must be taken into account and should be a mandatory data item for screening programmes. Maternal weight correction in the first trimester using free β-hCG and PAPP-A can be best achieved using the log-linear procedure. Copyright © 2003 John Wiley & Sons, Ltd.