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Masters Thesis

Clinical utility of expanded carrier screening: reproductive decisions of at-risk carrier couples

Mendelian (single-gene) conditions are individually rare, but when considered collectively are relatively common with a birth incidence as high as 1 in 280 (Srinivasan et al., 2010; Nazareth, Lazarin, & Goldberg, 2015). Advances in next generation sequencing technology have allowed for the development of panels that test over 100 diseases, allowing for pan-ethnic carrier screening in the general population (Ioannou, Delatycki, Massie, Hodgson, & Lewis, 2015). These expanded carrier screens can include all of the ACMG and ACOG-recommended diseases yet literature on the clinical utility of these results is scarce (Edwards et al., 2015). We surveyed at-risk carrier couples, identified from a nationwide population by an expanded carrier screen, to learn about their experience and reproductive decisions after their carrier status was reported. We identified 537 consecutive at-risk carriers who received their results between April 2014 and August 2015, had provided an email address, phone number or mailing address, and consented to be contacted for future research opportunities. Patients were tested using Counsyl’s Family Prep Screen, an expanded carrier screen testing up to 110 genes. At-risk carriers were those whose partners were also carriers for the same autosomal recessive disease. Eligible participants were invited to participate in an online survey via email, SMS text message, and paper mailing. In total, 79 completed the survey and 15 responses were excluded due to incomplete responses or a known family history of the condition. Indications for testing among the remaining 64 were routine screening, a fertility workup or investigation of pregnancy loss, ethnicity based carrier screening, consanguinity, or ultrasound anomalies. 70.3% (45) were not pregnant at the time of screening and 29.7% (19) had prenatal carrier screening. Of the participants who were not pregnant when they received their results, 62.2% (28) indicated that they would pursue alternative reproductive options, either IVF with PGD or prenatal diagnosis. 28.9% (13) indicated that they were not planning to pursue any alternative options based on the results. The remaining 8.9% (4) selected “other” and the responses were not indicative of a clear future direction. Open responses left by the participants who do not plan to pursue alternative options indicated that the main reason for this decision was the perceived severity of the condition (Lazarin et al., 2014): these respondents were carriers of moderate conditions and one severe condition with a common mutation known for a mild phenotype (biotinidase deficiency). Of the 29.7% (N=19) of participants who were pregnant when they received results, 42.1% (8) elected to have prenatal diagnosis and 57.9% (11) did not. When describing their reasons for not pursuing prenatal diagnosis, 2 participants reported that they had planned to have prenatal diagnosis but had a miscarriage before the procedure could be done. The rest (9) indicated that they did not consider the condition sufficiently severe that they would consider terminating the pregnancy. Of the 8 pregnancies that underwent prenatal diagnosis, 5 were unaffected and 3 were affected. Two of the affected pregnancies were terminated and one was continued. The majority of at-risk carrier couples used their results to make alternative reproductive decisions, demonstrating the clinical utility of this information. The perceived severity of the condition was a major factor in the decision making process with diseases classified as moderate (Lazarin et al., 2014) less likely to result in a change in reproductive behavior. Patients have the most options when carrier screening is done in a preconception setting.

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