This application allows estimation of risks of early-PE (delivery at <32 weeks gestation), preterm-PE (<37 weeks) and term-PE (≥37 weeks). It uses Bayes theorem to combine the prior risk from maternal factors and medical history with the results of various biophysical and biochemical measurements made at different stages in pregnancy.
Risk calculation is provided for the gestational age blocks of 11+0 to 14+1, 19+0 to 24+6, 30+0 to 34+6 and 35+0 to 37+6 weeks. Please note that when using biophysical and biochemical markers the measurements should be obtained within the same gestational age block.
Performance of screening
- Useful markers in the first trimester (11+0 to 14+1 weeks) are MAP, UTPI, PLGF and PAPP-A. Optimum screening by a combination of maternal factors, MAP, UTPI and PLGF can detect 89% of early-PE, 75% of preterm-PE and 47% of term-PE, at FPR of 10% (AmJOG1, AmJOG2).
- Useful markers in the second trimester (19+0 to 24+6 weeks) are MAP, UTPI, PLGF and sFLT-1. Optimum screening by a combination of maternal factors, MAP, UTPI and PLGF can detect 99% of early-PE, 85% of preterm-PE and 46% of term-PE, at FPR of 10%.
- Useful markers in the third trimester are MAP, UTPI, PLGF and sFLT-1. Screening at , 30+0 to 34+6 weeks can detect 98% of preterm-PE and 60% of term-PE and screening at 35+0 to 37+6 weeks can detect about 85% of term-PE, at FPR of 10%.
- This application allows calculation of risks for PE based on maternal factors alone and in combination with any of the biomarkers. Details on the performance of the various combinations are provided in the relevant publications.
- The maternal factor derived prior risk has a strong influence on the posterior risk. Therefore, the overall performance of screening in any given population depends on the distribution of various maternal factors in the study population.
- Measurement of MAP requires adherence to a standardized technique (click here).
- Measurement of UTPI requires adherence to a standardized technique (click here).
- Measurement of biochemical markers requires validated equipment and reagents. At present these are provided by DelfiaXpress from PerkinElmer, Kryptor from ThermoFisher and Elecsys from Roche.
- All measurements for biophysical and biochemical markers are expressed as multiples of the normal median (MoMs), adjusting for maternal factors that provide substantive contribution to their value (MAP, UTPI, PLGF, sFLT-1, PAPP-A). This application allows calculation of MoMs from the measurements of MAP and UTPI. However, MoM values for biochemical markers depend on maternal characteristics but also on the equipment and reagents used at a specific laboratory. You will therefore need to obtain the MoM values from your laboratory.
- In the calculation of MoMs and risks of PE, it is important to provide the gestational age at which the measurements are made. This application allows calculation of gestational age from fetal crown-rump-length in the first trimester or fetal head circumference in the second trimester.
Quality of measurements
This application allows you to carry out audits for your measurements of the various biomarkers. This is essential in providing a high quality screening service. If you want to audit your measurements please click here.
The median MoM value for each biomarker should be approximately 1.0 MoM. The audit function will highlight whether your values are outside acceptable limits:
- In the case of MAP and UTPI, you may need to retrain in taking appropriate measurements.
- In the case of biochemical markers, you should review the process of collection and transportation of samples to the laboratory and whether the laboratory uses the appropriate software and adjustments in the calculation of MoMs.
Click here to use the application.