Performance of a targeted cell-free DNA prenatal test for 22q11.2 deletion in a large clinical cohort.

OBJECTIVE: 22q11.2 deletion is more common than trisomies 18 and 13 combined, yet no routine approach to prenatal screening for this microdeletion has been established. This study evaluated the clinical sensitivity and specificity of a targeted cell-free DNA (cfDNA) test to screen for fetal 22q11.2 deletion in a large cohort, using blinded analysis of prospectively enrolled pregnancies and stored clinical samples. METHODS: In order to ensure that the analysis included a meaningful number of cases with fetal 22q11.2 deletion, maternal plasma samples were obtained by prospective, multicenter enrolment of pregnancies with a fetal cardiac abnormality and from stored clinical samples from a research sample bank. Fetal genetic status, as evaluated by microarray analysis, karyotyping with fluorescence in-situ hybridization or a comparable test, was available for all cases. Samples were processed as described previously for the Harmony prenatal test, with the addition of DANSR (Digital Analysis of Selected Regions) assays targeting the 3.0-Mb region of 22q11.2 associated with 22q11.2 deletion syndrome. Operators were blinded to fetal genetic status. Sensitivity and specificity of the cfDNA test for 22q11.2 deletion were calculated based on concordance between the cfDNA result and fetal genotype. RESULTS: The final study group consisted of 735 clinical samples, including 358 from prospectively enrolled pregnancies and 377 stored clinical samples. Of 46 maternal plasma samples from pregnancies with a 22q11.2 deletion, ranging in size from 1.25 to 3.25 Mb, 32 had a cfDNA result indicating a high probability of 22q11.2 deletion (sensitivity, 69.6% (95% CI, 55.2-80.9%)). All 689 maternal plasma samples without a 22q11.2 deletion were classified correctly by the cfDNA test as having no evidence of a 22q11.2 deletion (specificity, 100% (95% CI, 99.5-100%)). CONCLUSIONS: The results of this large-scale prospective clinical evaluation of the sensitivity and specificity of a targeted cfDNA test for fetal 22q11.2 deletion demonstrate that this test can detect the common and smaller, nested 22q11.2 deletions with a low (0-0.5%) false-positive rate. Although the positive predictive value (PPV) observed in this study population was 100%, the expected PPV in the general pregnant population is estimated to be 12.2% at 99.5% specificity and 41.1% at 99.9% specificity. The use of this cfDNA test to screen for 22q11.2 deletion could enhance identification of pregnancies at risk for 22q11.2 deletion syndrome without significantly increasing the likelihood of maternal anxiety and unnecessary invasive procedures related to a false-positive result. © 2021 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Calcaneal ultrasound attenuation and vitamin-D-receptor genotypes in celiac disease.

BACKGROUND: Osteopenia is common in patients with celiac disease and is believed to result from malnutrition. Osteoporosis in otherwise healthy individuals is related to genetically determined polymorphisms within the vitamin-D-receptor (VDR) gene. We hypothesized that in celiac patients particular genes of the VDR enhance the susceptibility for malnutrition-associated low-bone density. METHODS: We determined allelic frequencies within the VDR gene by restriction fragment length polymorphism analysis in 92 patients with celiac disease (age, 15-83 years). Thirty-eight patients were on a gluten-free diet; 54 patients did not adhere to a diet. The determined VDR polymorphisms in 111 unrelated newborns served as controls. Osteopenia was determined by means of ultrasound measurements of the calcaneus (n = 78). Bone turnover was estimated by osteocalcin determination (n = 60). RESULTS: There was no difference in the frequency of the VDR gene polymorphisms in patients with celiac disease compared with controls. Adjusted ultrasound measures of the calcaneus were low in 47% of patients, but there was no difference of the VDR gene frequencies in these patients compared with those with normal ultrasound results or controls. Bone turnover was higher in patients without a gluten-free diet (P = 0.02). Again, there was no association with any particular VDR gene. CONCLUSIONS: Patients with celiac disease frequently have osteopenia, which is not related to any of the determined genes within the VDR.

Genotypes of the vitamin-D-receptor gene and bone mineral density in Caucasoid postmenopausal females.

OBJECTIVE: To evaluate the relation of bone mineral density (BMD) to inherited polymorphisms within the gene coding for the vitamin D receptor (VDR) in postmenopausal women. METHODS: DNA samples from 163 post-menopausal women and from 112 controls were genotyped for common allelic determinants within the VDR gene as defined by the restriction enzyme sites for BsmI, ApaI, and TaqI. BMD was evaluated at the lumbar spine (L2-L4) by dual energy X-ray absorptiometry. Single restriction enzyme site polymorphisms as well as their joint genotypes were evaluated for their association with BMD in postmenopausal women. RESULTS: The three restriction site polymorphisms showed a close association indicating linkage disequilibrium (P < 0.0001). There was no relationship between any of the single restriction site polymorphisms and BMD. The distribution of the five most common joint genotypes among postmenopausal women and controls was similar. There was no relation of BMD and any of the five most common VDR genotype groups. Females more than 5 years after menopause had a significantly lower BMD than those less than 5 years after menopause (P < 0.001). This age-related decrease of BMD was also decernible within genotype groups. CONCLUSION: In our population, the postmenopausal period has a major influence on BMD, but BMD is not controlled significantly by any of the common allelic variations within the VDR gene.