Clinical utility of a new diagnostic genetic testing for prenatal screening in the Indian population

Prenatal screening using dual and quadruple marker testing is a cost-effective approach, but it has its limitations, potentially leading to false positives and negatives. Combining dual and quadruple marker testing with PregascreenTM reflex testing has proven effective. 

A recent study aimed to assess the clinical validity of the Metropolis PregascreenTM reflex testing approach in Indian women by evaluating prenatal screening using maternal biochemical dual and quadruple markers, karyotyping, and non-invasive prenatal testing via next-generation sequencing (NIPT-NGS).

The research analyzed retrospective data from 51,574 Indian women who underwent maternal marker screening between January 2021 and March 2022 at Metropolis Healthcare Limited, India. First and second-trimester screening utilized Roche and Siemens platforms, incorporating risk calculation through SSDW and PRISCA software, ultrasound findings, and biochemical values. NIPT reflex testing was conducted using Thermo Ion torrent S5 NGS systems, and karyotyping was performed on chronic villus sampling or amniocentesis.

Out of the total 51,574 women who chose the combined biochemical markers test (dual and quadruple), 1,394 cases (2.70%) were identified as high-risk, while 50,180 cases (97.28%) were categorized as low-risk. Among the high-risk cases, 483 women (34.65%) opted for NIPT, and 25 (1.79%) chose karyotyping reflex testing. After NIPT, 92% of dual marker high-risk cases and 94% of quadruple marker high-risk cases were reclassified as low risk. Similarly, 91% of dual marker high-risk cases and 93% of quadruple marker high-risk cases were reclassified as low risk after karyotyping.

Hence, both NIPT and karyotyping have similar abilities to rule out false positives. As a result, invasive screening as the initial diagnostic option can be avoided. Metropolis Pregascreen TM reflex testing, in conjunction with NIPT, aids in accurately identifying genuine high-risk cases for safer and more precise diagnosis.

NIPT offers a detection rate of over 99%, making it a valuable option. NGS-based NIPT demonstrates high sensitivity, specificity, and positive predictive value for tested trisomies, making it an excellent alternative to traditional maternal serum screening tests.

Source: Govalkar A, Banerjee M, Christy A, Rajyadhyaksha A, Jatale R, Almeida F, Chanekar M, Gawali Y, Dixit R B, Chadha K. Indian J Obstet Gynecol Res. 2023;10(3):335-341