Interpretation
The FMF algorithm has been externally validated by several studies in
various populations, showing comparable performance to that of the
original study. Nevertheless, one study showed that some algorithms
could underperform when applied to populations that were different to
the population where they were developed22. In this
study, we show that performance of the FMF algorithm in a Spanish
population was similar to the performance obtained in the original
study, further supporting the external validity of the FMF algorithm. By
contrast, the predictive ability of the Gaussian algorithm has not been
evaluated in other studies, aside from the original study where it was
first validated. It must be noted that the Gaussian algorithm was not
developed in our population, but just validated, since this algorithm
was constructed using previously published data from a large
meta-analysis. This might make this algorithm less likely to be
overfitted to our population and therefore, less likely to underperform
when applied to a different population. Since the first-trimester PE
screening and aspirin prescription has been implemented in most
countries across Europe, prospective external validation of the Gaussian
algorithm in untreated populations seems unlikely. Therefore, a
reasonable indirect approach to assess the predictive performance of the
Gaussian algorithm is to compare it with the FMF algorithm, which has
been extensively validated in various large populations. Although our
results cannot be considered an external validation of the Gaussian
algorithm, the similar accuracies of both algorithms suggest that the
FMF algorithm is unlikely to outperform the Gaussian algorithm in our
population where it is being routinely used in most maternities since
2018. For this reason, we believe that the Gaussian algorithm might be a
reasonable alternative to the FMF algorithm for those settings where the
latter cannot be applied dur to ultrasonographers performing UtAPI both
transabdominally and transvaginally of for settings measuring biomarkers
for the aneuploidy and PE screenings before 11 weeks.
Additionally, as seen in previous studies23, we
confirm that PAPP-A does not increase the predictive accuracy of any of
the algorithms when PlGF was being used; however, when PlGF is not
available, PAPP-A could increase DR by 5% with some marker
combinations.
Finally, we observed that a single measurement of MAP could decrease the
predictive accuracy of the FMF algorithm; therefore, the appropriate
methodology should be performed when using this algorithm.