Improving the Positive Predictive Value of Non-Invasive Prenatal Screening (NIPS)

PLoS One. 2017 Mar 1;12(3):e0167130. doi: 10.1371/journal.pone.0167130. eCollection 2017.

Abstract

We evaluated performance characteristics of a laboratory-developed, non-invasive prenatal screening (NIPS) assay for fetal aneuploidies. This assay employs massively parallel shotgun sequencing with full automation. GC sequencing bias correction and statistical smoothing were performed to enhance discrimination of affected and unaffected pregnancies. Maternal plasma samples from pregnancies with known aneuploidy status were used for assay development, verification, and validation. Assay verification studies using 2,085 known samples (1873 unaffected, 69 trisomy 21, 20 trisomy 18, 17 trisomy 13) demonstrated complete discrimination between autosomal trisomy (Z scores >8) and unaffected (Z scores <4) singleton pregnancies. A validation study using 552 known samples (21 trisomy 21, 10 trisomy 18, 1 trisomy 13) confirmed complete discrimination. Twin pregnancies showed similar results. Follow-up of abnormal results from the first 10,000 clinical samples demonstrated PPVs of 98% (41/42) for trisomy 21, 92% (23/25) for trisomy 18, and 69% (9/13) for trisomy 13. Adjustment for causes of false-positive results identified during clinical testing (eg, maternal duplications) improved PPVs to 100% for trisomy 21 and 96% for trisomy 18. This NIPS test demonstrates excellent discrimination between trisomic and unaffected pregnancies. The PPVs obtained in initial clinical testing are substantially higher than previously reported NIPS methods.

Publication types

  • Validation Study

MeSH terms

  • Chromosomes, Human / genetics*
  • False Positive Reactions
  • Female
  • Follow-Up Studies
  • Humans
  • Male
  • Mass Screening / methods*
  • Pregnancy
  • Prenatal Diagnosis / methods*
  • Trisomy / diagnosis*
  • Trisomy / genetics*

Grants and funding

This study and preparation of this manuscript were done as part of routine work at Quest Diagnostics. Athena Diagnostics and Celera Diagnostics are wholly owned subsidiaries of Quest Diagnostics. Quest Diagnostics provided support in the form of salaries for CMS, BA, DT, KZ, YL, KL, QN, PK, MM, JW, DR, JC, RO and WS, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. Athena/Quest Diagnostics provided support in the form of salaries for CB, ME, and CE, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. Celera/Quest Diagnostics provided support in the form of salary for DW, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.