Revista Brasileira de Ginecologia e Obstetrícia (Sep 2005)
Abordagem citogenética e molecular em material de abortos espontâneos Cytogenetic and molecular evaluation of spontaneous abortion samples
Abstract
OBJETIVOS: avaliar o desempenho da citogenética e das técnicas de hibridização in situ fluorescente (FISH) e reação em cadeia da polimerase (PCR) no estudo das aneuploidias cromossômicas numéricas e na determinação do sexo fetal em amostras de abortos espontâneos. MÉTODOS: duzentos e dezenove amostras de produtos de abortos espontâneos foram submetidas a estudo citogenético. Deste total, 40 amostras foram também submetidas à técnica de PCR-nested para a determinação do sexo fetal: 32 foram selecionadas devido à falha de crescimento no estudo citogenético e oito foram escolhidas ao acaso. Vinte amostras foram selecionadas para detecção de aneuploidias cromossômicas pela técnica de FISH, utilizando-se sondas para os cromossomos 13, 18, 21, X e Y: 13 casos foram submetidos a FISH devido à falha de crescimento no estudo citogenético e sete foram escolhidos ao acaso. Foi calculada a taxa de sucesso (obtenção de cariótipo) de cada técnica. Para comparação das taxas de sucesso foi utilizado o teste de chi2, sendo considerados significantes resultados com pPURPOSE: to evaluate the performance of cytogenetic analysis, fluorescent in situ hybridization (FISH) and polymerase chain reaction (PCR) in the study of numerical chromosomal anomalies and in fetal sex determination of spontaneous abortion material. METHODS: cytogenetic analysis was performed on 219 spontaneous abortion specimens. Forty of these cases were also submitted to fetal sex determination using nested-PCR. Thirty-two of these cases were selected due to failed cytogenetic culture and the other eight were selected randomly. Twenty samples were submitted to the FISH technique, using probes for chromosomes 13, 18, 21, X and Y. Thirteen of these samples were selected due to failed cytogenetic culture and the other seven were randomly selected. The success rates of each technique were compared using the chi2 test and an established p<0.05 level of significance. The results of samples submitted to more than one test were evaluated for accuracy, using the cytogenetic result as the gold standard. RESULTS: cytogenetic analysis was successful in 84.9% of the samples and in 51.1% of them the results were abnormal: 65.2% trisomy, 17.9% triploidy, 9.4% tetraploidy, 4.2% chromosome X monosomy, and 1.1% each for double trisomy, tetrasomy and structural abnormality. The most frequent trisomy was that of chromosome 16 (39%). The success rate of FISH and PCR techniques (90%) did nod differ significantly from the cytogenetic analysis. In all cases submitted to more than one test, the results were identical to those obtained through cytogenetic analysis. Samples that failed to grow on cytogenetic test and that were submitted to other techniques of molecular biology had a success rate of 87.5 and 84.6% for PCR and FISH, respectively. CONCLUSION: cytogenetic analysis of spontaneous abortions had a high success rate and chromosomal anomalies were identified in over half of the cases. Molecular biology techniques (PCR and FISH) complemented the cytogenetic study and proved to be reliable in the detection of numerical chromosomal anomalies and in fetal sex determination.
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