[Discordant Down syndrome risk calculation with low maternal serum markers: About five cases of digynic triploidies]

Abstract

Objective: We compare the risk of Down syndrome among five patients carrying a foetus with digynic triploidy and suggest a course of action for these particular serological profiles.

Methods: The concentrations of the different markers used are transformed into multiples of the median by using each of the three software types present on the French market which then determine the risk of Down syndrome.

Results: For comparable biochemical and ultrasound profiles, the risk of Down syndrome turns out to be vastly different depending on the type of software employed. The relevance of an immediate diagnostic procedure, of a cell free DNA test or of a basic ultrasound follow-up then arises, leading to a potentially variable care pathway for the patient.

Conclusions: This study confirms that for this type of biochemical profile, the laboratory's advisory service is fundamental, that a control ultrasound is essential and that an invasive procedure must be used almost invariably due to the extremely substantial risk factors.

Keywords: Aneuploidy risk calculation; Calcul de risque d’aneuploïdie; Digynic triploidy; Down syndrome screening; Dépistage de la trisomie 21; Marqueurs sériques maternels; Maternal serum markers; Triploïdie digynique.