Diagnostic performance of the noninvasive prenatal FetoGnost RhD assay for the prediction of the fetal RhD blood group status

Abstract

Purpose: To evaluate the diagnostic accuracy of a commercially available test kit for noninvasive prenatal determination of the fetal RhD status (NIPT-RhD) with a focus on early gestation and multiple pregnancies. Methods: The FetoGnost RhD assay (Ingenetix, Vienna, Austria) is routinely applied for clinical decision making either in woman with anti-D alloimmunization or in order to target the application of routine antenatal anti-D prophylaxis (RAADP) to women with a RhD positive fetus. Based on existing data in the laboratory information system the newborn’s serological RhD status was compared with NIPT RhD results. Results: Since 2009 NIPT RhD was performed in 2,968 pregnant women between week 5+6 and 40+0 of gestation (median 12+6) and conclusive results were obtained in 2,888 (97.30%) cases. Diagnostic accuracy was calculated from those 2244 (77.70%) cases with the newborn’s serological RhD status reported. The sensitivity of the FetoGnost RhD assay was 99.93% (95% CI 99.61% - 99.99%) and the specificity was 99.61% (95% CI 98.86% - 99.87%). No false positive or false negative NIPT RhD result was observed in 203 multiple pregnancies. Conclusion: NIPT RhD results are reliable when obtained with FetoGnost RhD assay. Targeted routine anti-D-prophylaxis can start as early as 11+0 weeks of gestation in singleton and multiple pregnancies.

Recommendation for validation and quality assurance of non‐invasive prenatal testing for foetal blood groups and implications for IVD risk classification according to EU regulations

“…If a laboratory makes minor modifications to an existing published protocol, fewer specimens are needed. Based on the extensive literature about the application of real‐time PCR for the determination of the foetal RHD status [7, 8, 12–25, 33–36], with real‐time PCR details published for >50,000 cases from several protocols [7, 12–25], the investigation of 100 specimens is sufficient for a performance evaluation of an assay using this well‐validated and published real‐time PCR technology in pregnancies of at least 10 weeks of gestation. Oligonucleotides and probes for RHD exon 5 and 7 have been verified in a multicentre study [37].…”

Nichtinvasiver Pränataltest zur Bestimmung des fetalen Rhesusfaktors

“…Die Empfehlung der Mu-RL zur gezielten Anti-D-Prophylaxe beschränkt sich auf Einlingsschwangerschaften, da sich der G-BA einer wissenschaftlichen Stellungnahme des Instituts für Qualität und Wirtschaftlichkeit im Gesundheitswesen (IQWiG) aus dem Jahr 2018 angeschlossen hat 10 . Frühere und seither veröffentlichte Studienergebnisse belegen eine Zuverlässigkeit des NIPT-RhD auch bei Mehrlingsschwangerschaften 11 , 12 , 13 , 14 .…”

“…Die Nukleinsäureextraktion erfolgte nach Zentrifugation aus 2 ml EDTA-Plasma nach Zusatz einer Extraktionskontrolle (IPC = interne Positivkontrolle) automatisiert (Qiasymphony SP, Qiagen, Hilden). Das Eluat wurde unter Verwendung des FetoGnost-Kit RhD (Ingenetix, Wien, Österreich) in dem Real-Time-PCR-Gerät Quantstudio 5 (Thermo Fisher Scientific Life-Technologies GmbH, Darmstadt) entsprechend einem publizierten Protokoll untersucht [14]. Ein Schwellenwert (Threshold) wurde zur Analyse von RHD Exon 5 und 7 bei 0,07 und bei der Analyse von Exon 10 sowie IPC bei 0,03 gesetzt (▶ Abb.…”