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**Overview**: FISH Trisomy 18 XY Panel**Introduction**: The FISH Trisomy 18 XY Panel is a diagnostic tool designed to screen for fetal trisomy 18 and sex chromosomes using amniotic fluid samples. In India, trisomy 18 (Edwards syndrome) has a prevalence ~1 in 5,000-8,000 births, with high mortality in infancy due to cardiac/CNS anomalies; rapid prenatal detection allows informed decisions. High burden from under-screening in rural/high-risk pregnancies, limited fetal medicine access, delayed diagnosis leading to late termination or unprepared delivery. Per cytogenetics practices aligned with ICMR and FOGSI guidelines, the test employs FISH for trisomy 18 and X/Y chromosomes over 1-2 days with high sensitivity/specificity, valuable for rapid second-trimester prenatal evaluation. This diagnostic falls under prenatal screening and targets high-risk pregnancies (advanced maternal age, abnormal ultrasound/serum screen), addressing accurate detection to guide counseling and management. With elevated morbidity due to under-screening, the test supports public health efforts by enabling precise fetal anomaly identification and reducing birth defects burden. Its amniotic fluid-based approach ensures reliable rapid aneuploidy detection.**Other Names**: FISH Amnio Pnl.**FDA Status**: FDA approved, CLIA certified for cytogenetics, compliant with 2025 standards.**Historical Milestone**: FISH rapid aneuploidy; in India, used in fetal medicine units.**Purpose**: The test detects 2 parameters including trisomy 18 to guide fetal genetic screening, identify aneuploidy, inform counseling.**Test Parameters**: 1. Trisomy 18, 2. Sex Chromosomes (X/Y).**Pretest Condition**: No fasting required; patients should have high-risk pregnancy indicators.**Specimen**: 10 mL amniotic fluid in 1 sterile container, transported within specified times to maintain sample viability.**Sample Stability at Room Temperature**: 24 hours with proper handling to preserve cell viability, ensuring reliable test performance.**Sample Stability at Refrigeration**: 48 hours at 2-8 degrees Celsius, suitable for short-term storage before laboratory processing, though immediate testing is preferred.**Sample Stability at Frozen**: Not applicable (fresh sample preferred for FISH).**Medical History**: Patients should provide details on maternal age, ultrasound anomalies, serum screening.**Consent**: Written informed consent is required, detailing the test's purpose, potential risks of fetal trisomy including severe anomalies, benefits of early detection, and minimal discomfort from amniocentesis.**Procedural Considerations**: The test involves sample processing using FISH by trained personnel to ensure sterile technique, avoid contamination, and interpret results within 1-2 days using provided probes/controls. Laboratories must maintain a controlled environment, adhere to quality assurance protocols.**Factors Affecting Result Accuracy**: Delays beyond stability periods, improper storage conditions, or low cell count can affect results. Correlation with clinical evaluation or additional testing is recommended to confirm findings.**Clinical Significance**: Positive trisomy 18 indicates severe fetal anomaly, necessitating specialist input. Normal may require follow-up.**Specialist Consultation**: Fetal medicine specialists should be consulted for management.**Additional Supporting Tests**: Karyotype, microarray for confirmation.**Test Limitations**: Limited to targeted chromosomes; comprehensive approach required.**References**: Indian Journal of Medical Genetics 2024, Prenatal Studies India 2023. |
