Chromosomal Microarray (CMA 750K) – Affymetrix CytoScan 750K

Overview

Chromosomal Microarray Analysis (CMA 750K) using the Applied Biosystems / Affymetrix CytoScan™ 750K platform is a high-resolution genetic test designed to detect chromosomal abnormalities, including microdeletions, microduplications, copy number variations (CNVs), aneuploidies, and regions of loss of heterozygosity (LOH). It is widely used for evaluating developmental disorders, congenital anomalies, autism spectrum disorders, intellectual disability, infertility, recurrent pregnancy loss, and prenatal abnormalities.

Technology

The Affymetrix CytoScan 750K Array contains:

• Approximately 750,000 genomic markers
• Around 550,000 non-polymorphic CNV probes
• Around 200,000 SNP probes for enhanced genomic analysis
• Genome-wide coverage with high sensitivity and specificity

What the Test Detects

• Chromosomal gains and losses
• Microdeletion & microduplication syndromes
• Copy Number Variations (CNVs)
• Aneuploidies
• Uniparental Disomy (UPD)
• Loss of Heterozygosity (LOH)
• Regions of homozygosity
• Submicroscopic chromosomal abnormalities not detectable by routine karyotyping

Clinical Indications

This test is recommended for:

• Developmental delay
• Intellectual disability
• Autism Spectrum Disorder (ASD)
• Multiple congenital anomalies
• Dysmorphic features
• Epilepsy/seizure disorders
• Prenatal abnormal ultrasound findings
• Recurrent pregnancy loss
• Infertility evaluation
• Products of conception analysis
• Hematological malignancy research and chromosomal abnormality assessment

Sample Requirements

Common sample types include:

• Peripheral blood (EDTA)
• Amniotic fluid
• Chorionic villus sample (CVS)
• Bone marrow
• Cord blood
• Buccal swab
• Tissue samples
• Products of conception (POC)

Advantages

• Higher resolution than conventional karyotyping
• Detects cryptic chromosomal abnormalities
• Genome-wide comprehensive analysis
• Improved diagnostic yield in genetic disorders
• Useful for prenatal and postnatal genetic evaluation
• Supports accurate clinical decision-making

Limitations

This test generally does NOT detect:

• Balanced translocations
• Low-level mosaicism
• Single gene mutations
• Small insertions/deletions
• Point mutations
• Mitochondrial disorders

Turnaround Time

• Approximately 2–3 weeks depending on sample type and laboratory workflow.

Useful For

• Pediatric genetics
• Prenatal diagnosis
• Neurological disorders
• Reproductive medicine
• Oncology and hematological research
• Rare disease evaluation

Interpretation

Results are interpreted according to ACMG guidelines and categorized as:

• Pathogenic
• Likely pathogenic
• Variant of Uncertain Significance (VUS)
• Likely benign
• Benign