Cross-trimester repeated measures testing for Down’s syndrome screening: an assessment

Abstract

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Maternal serum soluble fms‐like tyrosine kinase‐1 at 22 and 32 weeks in the prediction of pre‐eclampsia

“…The findings of combining second-and early third-trimester serum sFlt-1 in screening for PE are compatible with those of combining first-and second-trimester serum PAPP-A in screening for trisomy 21 11,12 . These results provide further evidence in favor of the concept that certain combinations of highly correlated markers, some of which individually have poor discriminatory power, can improve the overall performance of screening.…”

Repeat measurements of uterine artery pulsatility index, mean arterial pressure and serum placental growth factor at 12, 22 and 32 weeks in prediction of pre‐eclampsia

“…In both unaffected pregnancies and those that develop PE, there is a high correlation between second‐ and early third‐trimester measurements of serum sFlt‐1. These results provide evidence in favor of the concept that certain combinations of highly correlated markers, some of which individually have poor discriminatory power, can improve the overall performance of screening.…”

“…The prevailing view in multimarker screening tests for pregnancy complications is that, first, the individual markers should have good discriminatory power and second, there should be low correlations between markers so that they provide independent information. However, this view has been challenged by the demonstration that certain combinations of highly correlated markers, some of which individually have poor discriminatory power, can improve the overall performance of screening. For example, serum pregnancy‐associated plasma protein‐A (PAPP‐A) in the second trimester is a very poor marker for trisomy 21, but the addition of second‐trimester PAPP‐A to first‐trimester PAPP‐A results in substantial improvement in the performance of screening by the latter.…”

“…However, this view has been challenged by the demonstration that certain combinations of highly correlated markers, some of which individually have poor discriminatory power, can improve the overall performance of screening. For example, serum pregnancy‐associated plasma protein‐A (PAPP‐A) in the second trimester is a very poor marker for trisomy 21, but the addition of second‐trimester PAPP‐A to first‐trimester PAPP‐A results in substantial improvement in the performance of screening by the latter. This is the consequence of a high correlation between first‐ and second‐trimester levels of PAPP‐A in both euploid and trisomic pregnancies.…”

Secondary tests for stratification of risk for atherosclerosis

“…The sampling method used in case-control selection from larger cohorts can significantly affect the results of any analysis 21 . Use of a single pass assessment of the model will give a false impression of the performance: a non-parametric boot-strapping technique as described for other screening populations where multiple data sets are hard to acquire should have been used to improve assessment, in particular to identify confidence intervals for the effectiveness of the test 22 . Further work therefore needs to be carried out to assess whether this risk stratification panel would be clinically useful.…”