Diagnóstico prenatal y array-CGH II: gestaciones de bajo riesgo

Prenatal cytogenetic diagnosis: results obtained in the specialized laboratory of Clínica Universitaria Colombia from 2013 to 2019

OBJECTIVE

Prenatal cytogenetic evaluation is a key tool for identifying alterations in pregnant women with high risk for fetal chromosomal abnormalities (CA). In Colombia, there are not large-scale reports about the prevalence and pattern of CA in prenatal cytogenetic analysis.

METHOD

A descriptive study was performed from registers of prenatal cytogenetic analysis on amniotic fluid (AF), chorionic villus biopsy (CVS), and fetal blood (FB) samples sent to the specialized laboratory of the Clínica Universitaria Colombia between 2013 and 2019.

RESULTS

The prevalence of CA was 20.9%. The trisomies 21, 18, 13, and monosomy X were the most frequent aneuploidies, and the derivative chromosomes were the most frequent structural abnormalities. Although the rate of CA was higher in women over the age of 35 years old; monosomy X, unbalanced rearrangements, and microduplications were associated with the group of women under the age of 35 (p < .05). Trisomies 21 and 18 were the most common aneuploidies identified by FISH and were found to be altered in 52% of the aCGH studies. Ultrasonographic markers associated with CA were the most frequent clinical indication.

CONCLUSION

In Colombia, the invasive prenatal cytogenetic analysis continues being an important diagnostic tool available for pregnant women with high risk for fetal CA.

Karyotype versus genomic hybridization for the prenatal diagnosis of chromosomal abnormalities: a metaanalysis

OBJECTIVE

The aim of this study was to determine the diagnostic accuracy of comparative genomic hybridization (CGH) compared with karyotyping for the detection of numerical and structural chromosomal alterations in prenatal diagnosis.

STUDY DESIGN

A metaanalysis was performed using searches of PubMed, EMBASE, CENTRAL, Cochrane Register of Diagnostic Test Accuracy Studies, Google Scholar, gray literature, and reference manuals. No language restriction was imposed. We included cross-sectional, cohort, and case-control studies published from January 1980 through March 2014 in the analysis. Studies of pregnant women who received chorionic villus biopsies, amniocentesis, or cordocentesis and then underwent CGH and karyotype analysis were included. Two independent reviewers assessed each study by title, abstract, and full text before its inclusion in the analysis. Methodological quality was assessed using QUADAS2, and a third reviewer resolved any disagreement. Conclusions were obtained through tests (sensitivity, specificity, and likelihood ratios) for the presence of numerical and structural chromosomal abnormalities. The reference used for these calculations was the presence of any abnormalities in either of the 2 tests (karyotype or CGH), although it should be noted that in most cases, the karyotyping test had a lower yield compared with CGH. Statistical analysis was performed in RevMan 5.2 and the OpenMeta[Analyst] program.

RESULTS

In all, 137 articles were found, and 6 were selected for inclusion in the systematic review. Five were included in the metaanalysis. According to the QUADAS2 analysis of methodology quality, there is an unclear risk for selection bias and reference and standard tests. In the other elements (flow, time, and applicability conditions), a low risk of bias was found. CGH findings were as follows: sensitivity 0.939 (95% confidence interval [CI], 0.838-0.979), I(2) = 82%; specificity 0.999 (95% CI, 0.998-1.000), I(2) = 0%; negative likelihood ratio 0.050 (95% CI, 0.015-0.173), I(2) = 0%; and positive likelihood ratio 1346.123 (95% CI, 389-4649), I(2) = 0%. Karyotype findings were as follows: sensitivity 0.626 (95% CI, 0.408-0.802), I(2) = 93%; specificity 0.999 (95% CI, 0.998-1.000), I(2) = 0%; negative likelihood ratio 0.351 (95% CI, 0.101-1.220), I(2) = 0%; and positive likelihood ratio 841 (95% CI, 226-3128), I(2) = 10%.

CONCLUSION

This systematic review provides evidence of the relative advantage of using CGH in the prenatal diagnosis of chromosomal and structural abnormalities over karyotyping, demonstrating significantly higher sensitivity with similar specificity.

Prenatal Diagnosis of Chromosome Abnormalities: A 13-Year Institution Experience

Objective: To analyze trends in screening and invasive prenatal diagnosis of chromosome abnormalities (CA) over a 13-year period and correlate them to changes in the national prenatal screening policy. Methods: We retrospectively reviewed Down syndrome (DS) screening tests and fetal karyotypes obtained by prenatal invasive testing (IT) in our fetal medicine unit between January 1999 and December 2011. Results: A total of 24,226 prenatal screening tests for DS and 11,045 invasive procedures have been analyzed. Over a 13-year period, utilization of non-invasive screening methods has significantly increased from 57% to 89%. The percentage of invasive procedures has declined from 49% to 12%, although the percentage of IT performed for maternal anxiety has increased from 22% to 55%. The percentage of detected CA increased from 2.5% to 5.9%. Overall, 31 invasive procedures are needed to diagnose 1 abnormal case, being 23 procedures in medical indications and 241 procedures in non-medical indications. Conclusions: Our experience on screening and invasive prenatal diagnostic practice shows a decrease of the number of IT, with a parallel decline in medical indications. There is an increasing efficiency of prenatal screening program to detect CA. Despite the increasing screening policies, our population shows a growing request for prenatal IT. The a priori low risk population shows a not negligible residual risk for relevant CA. This observation challenges the current prenatal screening strategy focused on DS; showing that the residual risk is higher than the current cut-off used to indicate an invasive technique.