Screening

Maternal plasma cell-free DNA is a highly effective form of early prenatal screening of common trisomies (21, 18, 13) after 10 weeks’ gestation (II-2A). Currently, offering maternal plasma cell-free DNA to all women as a primary screening method is not fiscally feasible in most provinces. Offering cell-free DNA in a … Maternal plasma cell-free DNA is a highly effective form of early prenatal screening of common trisomies (21, 18, 13) after 10 weeks’ gestation (II-2A). Currently, offering maternal plasma cell-free DNA to all women as a primary screening method is not fiscally feasible in most provinces. Offering cell-free DNA in a contingent model is an affordable option that has the potential to achieve improved performance while maintaining the benefits of conventional screening serum analyte and early ultrasound (III). View more

Avoidance of invasive testing

Pregnant women 10week of gestation or more with high-risk of fetal anueploidy. Participating in the Quebec Prenatal Screening Program (public).

Is research allowed on the sample after clinical testing is complete? Help
no

MPSS read counts and chromosomal ratios.

None/not applicable

Clinical follow up with genetic counselling and volountary definitive diagnosis

Tests performed
Entire test performed in-house

Sensitivity ≥ 99% for T13, T18 and T21 Specificity ≥ 99.8% for T13, T18 and T21 Accuracy ≥ 99.3% for T13, T18 and T21 Based on 1933 high risk pregnant women samples (212 aneuploid pregnancies confirmed by caryotype or equivalent)

Women who are considering undergoing maternal plasma cell-free DNA (cfDNA) screening should be informed that: • It is a highly effective screening test for the common fetal trisomies (21, 18, 13), performed after 10 weeks’ gestation (II-1A). • There is a possibility of a failed test (no result available), false … Women who are considering undergoing maternal plasma cell-free DNA (cfDNA) screening should be informed that: • It is a highly effective screening test for the common fetal trisomies (21, 18, 13), performed after 10 weeks’ gestation (II-1A). • There is a possibility of a failed test (no result available), false negative or positive fetal result, and an unexpected fetal or maternal result (II-1A). • All positive cfDNA screening results should be confirmed with invasive fetal diagnostic testing prior to any irrevocable decision (II-1B). • Management decisions, including termination of pregnancy, require diagnostic testing and should not be based on maternal plasma cfDNA results alone because it is not a diagnostic test (II-2B). • If a fetal structural abnormality is identified in a woman regardless of previous screening test results, the woman should undergo genetic counselling and be offered invasive diagnostic testing with rapid aneuploidy detection and reflex to microarray analysis if rapid aneuploidy detection is normal or inconclusive (II-2B). • Although cfDNA screening for aneuploidy in twin pregnancy is available, there is less validation data than for a singleton pregnancy and it should be undertaken with caution (II-2C). • Routine cfDNA screening for fetal microdeletions is not currently recommended (II-2B). View more

Is proficiency testing performed for this test? Help
No

Method used for proficiency testing: Help
Formal PT program

PT Provider: Help
College of American Pathologists, CAP

Description of PT method: Help
Regular analysis of plasma samples from pregnant women with return of results to CAP and independent performance analysis.

Description of internal test validation method: Help
Prospective head-to-head comparison of accuracy of two sequencing platforms for screening for fetal aneuploidy by cell-free DNA

Software used to interpret novel variations Help
not applicable

Laboratory's policy on reporting novel variations Help
not applicable