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- Title
Autocorrelation and cross-correlation between hCGβ and PAPP-A in repeated sampling during first trimester of pregnancy.
- Authors
Nørgaard, Pernille; Wright, Dave; Ball, Susan; Newell, Paul; Kirkegaard, Ida; Petersen, Olav Bjørn; Uldbjerg, Niels; Tørring, Niels; Jørgensen, Finn Stener; Friis-Hansen, Lennart; Ekelund, Charlotte; Tabor, Ann; Sørensen, Steen
- Abstract
Background: Theoretically, repeated sampling of free β-human chorionic gonadotropin (hCGβ) and pregnancy associated plasma protein-A (PAPP-A) in the first trimester of pregnancy might improve performance of risk assessment of trisomy 21 (T21). To assess the performance of a screening test involving repeated measures of biochemical markers, correlations between markers must be estimated. The aims of this study were to calculate the autocorrelation and cross-correlation between hCGβ and PAPP-A in the first trimester of pregnancy and to investigate the possible impact of gestational age at the first sample and time between sampling on the correlation. Methods: A prospective study was conducted including 3891 unaffected singleton pregnancies. Two measurements of hCGβ and PAPP-A were obtained during the first trimester in each pregnancy. Correlations between the four parameters, hCGβ first, hCGβ second, PAPP-A first and PAPP-A second, were estimated and presented in terms of Pearson's r coefficients. Furthermore, the correlation between paired samples as a function of time between samples was investigated. Results: The study demonstrated high correlation between first and second samples of hCGβ and PAPP-A with a correlation coefficient of 0.80 and 0.79, respectively. By contrast, the correlations between hCGβ and PAPP-A were low. In addition, the study demonstrated that the correlation between paired samples of hCGβ and PAPP-A decreases with earlier gestational age at the first sample and with increasing time between samples. Conclusions: We have developed a parameter set in terms of correlations between biochemical markers, which can be incorporated into a T21 screening algorithm based on repeated measures within the first trimester.
- Subjects
AUTOCORRELATION (Statistics); CROSS correlation; CHORIONIC gonadotropins; BLOOD proteins; PREGNANCY
- Publication
Clinical Chemistry & Laboratory Medicine, 2013, Vol 51, Issue 9, p1781
- ISSN
1434-6621
- Publication type
Article
- DOI
10.1515/cclm-2012-0805