D H Ledbetter1, J M Zachary, J L Simpson
1Institute for Molecular Genetics, Baylor College of Medicine, Houston, TX 77030.
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This study evaluated the accuracy of chorionic villus sampling (CVS) in detecting fetal genetic abnormalities across nine U.S. centers. Out of 11,473 procedures, 99.7% provided successful cytogenetic results using direct, culture, or combined methods. A small percentage of patients needed a second procedure due to diagnostic uncertainty or contamination. The study found no errors in detecting common trisomies like 21, 18, and 13. However, rare aneuploidies and structural abnormalities sometimes led to false positives, suggesting the need for follow-up with amniocentesis. Mosaicism occurred in 0.8% of cases, with higher confirmation rates in culture methods. Maternal cell contamination affected 1.8% of culture results but rarely caused diagnostic errors. These findings support the use of both direct and culture methods to improve prenatal genetic screening accuracy.
Area of Science:
Background:
Current prenatal screening methods rely heavily on cytogenetic analysis to detect fetal abnormalities. While chorionic villus sampling (CVS) is a common diagnostic tool, its accuracy and limitations remain areas of active investigation. Prior research has shown that CVS can provide early genetic insights, but concerns about false positives and diagnostic errors persist. This gap motivated the U.S. NICHD collaborative study to evaluate the diagnostic accuracy of CVS across multiple centers. That uncertainty drove the need for a large-scale assessment of cytogenetic outcomes. No prior work had resolved the frequency of diagnostic errors and false positives in real-world clinical settings. Researchers aimed to clarify the reliability of direct and culture methods used in CVS. The study also sought to identify the rate of maternal cell contamination and its impact on results. Understanding these factors is essential for improving prenatal care and diagnostic confidence.
Purpose Of The Study:
The study reported a 99.7% success rate in obtaining cytogenetic diagnoses from 11,473 chorionic villus sampling procedures.
Thirty-two percent of cases used a combination of direct and culture methods to obtain diagnostic results.
A second procedure was needed in 1.1% of cases due to laboratory failures, maternal cell contamination, or ambiguous results.
False positives included tetraploidy, trisomy 7, and rare trisomies like 3, 8, 11, 15, 16, 20, and 22.
The U.S. NICHD collaborative study aimed to assess the diagnostic accuracy of chorionic villus sampling (CVS) across nine clinical centers. The primary goal was to determine the success rate of cytogenetic diagnosis using direct and culture methods. Researchers also sought to evaluate the frequency of false positives and false negatives in detecting fetal abnormalities. This study focused on the reliability of results for common trisomies and sex chromosome aneuploidies. The motivation stemmed from clinical concerns about misdiagnosis and maternal cell contamination. By analyzing 11,473 procedures, the study aimed to provide data on diagnostic accuracy. The results could inform best practices for follow-up procedures like amniocentesis. This work contributes to improving the safety and reliability of prenatal genetic screening.
Main Methods:
The U.S. NICHD collaborative study collected cytogenetic data from 11,473 chorionic villus sampling procedures across nine centers. Researchers used the direct method, culture method, or a combination of both to obtain results. Diagnostic success was defined as a successful cytogenetic diagnosis in 99.7% of cases. The study tracked reasons for repeat procedures, including laboratory failures and maternal cell contamination. Aneuploidy detection involved analyzing trisomies for chromosomes 21, 18, and 13. Researchers also assessed false positives and false negatives in rare aneuploidies. Structural abnormalities were evaluated using both direct and culture methods. The study compared outcomes between direct and culture methods to identify trends in diagnostic accuracy.
Main Results:
The study found a 99.7% success rate in obtaining cytogenetic diagnoses from 11,473 CVS procedures. Most results came from the culture method (42%), direct method (26%), or a combination (32%). A total of 1.1% of patients required a second procedure due to diagnostic uncertainty. No diagnostic errors were observed for trisomies of chromosomes 21, 18, and 13. One case of non-mosaic 47,XXX led to a false-positive termination, later corrected by cultured cells. Thirteen false positives involved rare aneuploidies like tetraploidy and trisomy 7. Two structural abnormalities detected in the direct method were not confirmed in cultured samples. Eight false negatives were observed in the direct method, including one trisomy 18 and seven mosaics.
Conclusions:
The U.S. NICHD collaborative study concluded that chorionic villus sampling (CVS) has a high success rate in providing cytogenetic diagnoses. Researchers found no diagnostic errors for common trisomies like 21, 18, and 13. False positives were observed in rare aneuploidies, suggesting the need for follow-up with amniocentesis. Structural abnormalities detected in the direct method were not always confirmed in cultured samples. Mosaicism occurred in 0.8% of cases, with higher confirmation rates in the culture method. Maternal cell contamination affected 1.8% of culture results but rarely led to diagnostic errors. One case of incorrect sex prediction due to maternal contamination was reported. The study supports the use of both direct and culture methods to improve diagnostic accuracy.
Mosaicism was confirmed as fetal mosaicism in 24% of culture method cases, compared to 10% in direct method cases.
The culture method had a 1.8% maternal cell contamination rate, with only one case leading to incorrect sex prediction.