Algorithm development and diagnostic accuracy testing for non-invasive foetal RHD genotyping: an Indian experience.

Area of Science:

• Genetics
• Maternal-Fetal Medicine
• Molecular Diagnostics

Background:

• Cell-free fetal DNA (cffDNA) in maternal plasma allows non-invasive fetal RHD genotyping.
• This technique avoids risks associated with invasive prenatal procedures.
• It is standard for managing alloimmunized women and for targeted antenatal prophylaxis.

Purpose of the Study:

• To evaluate the diagnostic accuracy of non-invasive fetal RHD genotyping using cffDNA.
• To establish the feasibility of routine antenatal RhD screening in India.

Main Methods:

• Extracted cffDNA from plasma of 217 RhD-negative pregnant women (10-34 weeks gestation).
• Determined fetal RHD genotype via real-time PCR amplification of RHD exons.
• Compared results with cord blood serological typing at birth.

Main Results:

• Achieved 100% diagnostic accuracy, sensitivity, and specificity in 209 women with conclusive results.
• Overall diagnostic accuracy and sensitivity exceeded 95% when including inconclusive samples.
• Fetal RHD genotyping was successful from the 10th week of gestation.

Conclusions:

• Non-invasive fetal RHD genotyping using cffDNA demonstrates high accuracy and sensitivity.
• The method is suitable for routine diagnostic use in RhD-negative pregnant women in India.
• This approach can benefit the Indian antenatal population by enabling targeted prophylaxis and management.