A comparison of sample collection methods for quantifying cell-free fetal neurodevelopment transcripts in amniotic fluid

Performance of Zika Assays in the Context of Toxoplasma gondii, Parvovirus B19, Rubella Virus, and Cytomegalovirus (TORCH) Diagnostic Assays

Infections during pregnancy that may cause congenital abnormalities have been recognized for decades, but their diagnosis is challenging. This was again illustrated with the emergence of Zika virus (ZIKV), highlighting the inherent difficulties in estimating the extent of pre- and postnatal ZIKV complications because of the difficulties in establishing definitive diagnoses. We reviewed the epidemiology, infection kinetics, and diagnostic methods used for Toxoplasma gondii, parvovirus B19, rubella virus, and cytomegalovirus (TORCH) infections and compared the results with current knowledge of ZIKV diagnostic assays to provide a basis for the inclusion of ZIKV in the TORCH complex evaluations. Similarities between TORCH pathogens and ZIKV support inclusion of ZIKV as an emerging TORCH infection. Our review evaluates the diagnostic performance of various TORCH diagnostic assays for maternal screening, fetal screening, and neonatal screening. We show that the sensitivity, specificity, and positive and negative predictive value of TORCH complex pathogens are widely variable, stressing the importance of confirmatory testing and the need for novel techniques for earlier and accurate diagnosis of maternal and congenital infections. In this context it is also important to acknowledge different needs and access to care for different geographic and resource settings.

Measuring fetal brain and lung transcripts in amniotic fluid supernatant: a comparison of digital PCR and RT-qPCR methods

PURPOSE

Amniotic fluid (AF) cell-free RNA is a promising source of information regarding fetal physiology. Digital PCR (dPCR) is a direct approach to nucleic acid detection that reports absolute transcript copy number. The aim of this study was to compare quantification of cell-free fetal brain and lung RNA transcripts in AF by reverse transcription-qPCR (RT-qPCR) and dPCR.

MATERIAL AND METHODS

Prospective hospital-based study was performed in 2016-2017. Pulmonary genes were quantified in term AF samples collected at elective cesarean birth; neurodevelopmental genes were measured in preterm samples (<34 weeks) obtained from women undergoing clinically-indicated amniocentesis.

RESULTS

All 11 women in the term cohort had three lung transcripts and a reference gene successfully amplified from their AF supernatant using RT-qPCR and dPCR. SFTPC was the most abundant lung transcript, present in higher concentrations than the reference gene in seven of the eleven samples. Neurodevelopmental gene transcripts in 12 preterm pregnancies were less reliably detected by both methods and were present in low copy numbers (<10 copies/μl). We observed significant positive correlations between transcript quantification by RT-qPCR and dPCR.

CONCLUSION

This study confirms the presence of several potential mRNA markers of lung and brain development with dPCR and RT-qPCR, and a high correlation between the two methods. Transcripts of presumed fetal brain origin are present in very low copy numbers, which presents challenges to their feasibility as biomarkers of neurodevelopment.