Genetic analysis of products of conception. Should we abandon classic karyotyping methodology?

Abstract

Objective: To compare the results obtained by the classic and molecular methodology in the analysis of products of conception, the advantages and disadvantages of each method. Methods: Retrospective non-randomized analysis of results obtained from product of conception samples submitted to genetic evaluation, from 2012 to 2017. The evaluations were performed using cytogenetics and/or chromosomal microarray analysis or arrays. Results: Forty samples were analyzed using classic cytogenetics, of which 10% showed no cell growth, 50% had normal results and 40% had abnormalities. Of the 41 cases sent for array analysis it was not possible to obtain results in 7.3%, 39.5% were normal and 60.5% had abnormalities. There was no statistical difference among the results (p=0.89). Most abnormal results were seen till 9 weeks' gestation. The later abnormal miscarriage was seen at 28 weeks' gestation, with karyotype 46,XX,del(15) (q26.2-qter). The results are corroborated by the international literature. Conclusion: Classic cytogenetics and array techniques showed comparable results on the type of alteration observed. Array analysis is preferable to cell culture in delayed abortions, while cytogenetics is more able to show polyploidies. Both have the same growth failure rates when product of conception tissue is not properly collected.

Cytogenetic Analysis of Sporadic First-Trimester Miscarriage Specimens Using Karyotyping and QF-PCR: A Retrospective Romanian Cohort Study

“…Recent studies have proven the fact that the type of tissue sample collected is critical to cell growth success and subsequent karyotype analysis, with placental villi being the highest (>80%) and fetal parts being the lowest (<40%) in terms of cell culture success [ 54 , 55 ]. There is a reported 10–40% cell growth failure determined by factors such as the period of time between the moment of the loss and the sample collection, and the bacterial or fungal contamination of the sample [ 56 , 57 ]. It has been suggested that abnormal chorionic villus cells may show impaired in vitro proliferation in long-term culture, leading to the underestimation of the abnormality rate [ 15 ].…”

Non‐invasive cell‐free DNA‐based approach for the diagnosis of clinical miscarriage: A retrospective study

“…17 Cytogenetic analyses have traditionally determined genetic causes for miscarriage and the recurrence risk 18,19 ; however, they depend on cell culture of products of conception (POC) and a well-standardised methodology in routine laboratory use. 20 While representing the gold standard for studying structural rearrangements, karyotyping suffers from limited resolution in detecting copy number variations (CNVs) below 5-10 Mb, 21,22 a high failure rate (10-40%) due to poor tissue quality, and a significant lag (2-6 weeks) in obtaining results. 18 The informative rate for POC analysis has increased to ~80% following the advent of DNA-based analytical methods [23][24][25][26][27][28][29] ; however, molecular/cytogenetic approaches require fresh, uncontaminated and unfixed tissue to identify fetal tissue and perform DNA extraction/cell culture, which carries the potential risk of maternal cell contamination (MCC) and misdiagnosis.…”

“…Chromosomal abnormalities occur in ~60% of miscarriages 16 and <1% of live births when prenatal diagnosis is not performed 17 . Cytogenetic analyses have traditionally determined genetic causes for miscarriage and the recurrence risk 18,19 ; however, they depend on cell culture of products of conception (POC) and a well‐standardised methodology in routine laboratory use 20 . While representing the gold standard for studying structural rearrangements, karyotyping suffers from limited resolution in detecting copy number variations (CNVs) below 5–10 Mb, 21,22 a high failure rate (10–40%) due to poor tissue quality, and a significant lag (2–6 weeks) in obtaining results 18 …”

Maternal cell contamination in embryonic chromosome analysis of missed abortions

“…On the other hand, Giemsa banding (G‐banding) method is cheaper but the POC samples must be viable and free from bacterial contamination to obtain successful results in this method. It is said that the possibility of not obtaining results is about 10% in both CMA and G‐banding method 11 …”

“…It is said that the possibility of not obtaining results is about 10% in both CMA and G-banding method. 11 During embryonic chromosome examination, maternal cells contaminate the POCs at a certain rate. In the G-banding method, once contamination occurs, it is difficult to determine whether the result belongs to fetal chromosome or maternal chromosome.…”