Karyotype Analysis (Cytogenetics)

ISCN 2020 chromosome analysis by G-banding — prenatal, constitutional, and hematology-oncology

10–14 business days (prenatal STAT: 7 days)GTG-banding (G-banding, trypsin + Giemsa) at 550-band resolutionPeripheral blood (lithium-heparin), bone marrow, amniotic fluid (15–20 mL), chorionic villi (CVS), products of conception, skin fibroblasts, or cord blood

What is this test?

A karyotype is a microscopic photograph of all 46 chromosomes arranged in pairs. It remains the gold-standard test for detecting whole-chromosome abnormalities (for example, trisomy 21 / Down syndrome, Turner syndrome, Klinefelter syndrome), balanced rearrangements (translocations, inversions) that cannot be seen by DNA-based tests, and mosaicism. At IMC Genomics the karyotype is prepared by our ISO 15189:2022–accredited cytogenetics laboratory using GTG-banding at 550-band resolution and reported in full ISCN 2020 nomenclature. Every report includes images of the karyogram and metaphase spreads for documentation and second-opinion review.

Key Benefits

Gold-Standard Chromosomal Diagnosis

Karyotype remains the only test that visualizes balanced translocations, inversions, and marker chromosomes — abnormalities that DNA-based tests (microarray, NIPT, WES) cannot detect.

ISCN 2020 + ACMG + E-CA Compliant

Every report follows the International System for Human Cytogenomic Nomenclature (ISCN 2020), ACMG 2019 cytogenomics standards, and European Cytogeneticists Association (E-CA) General Guidelines v1.01 — the three standards that govern accredited cytogenetics worldwide.

Karyogram + Metaphase Images Included

Every PDF report contains a full karyogram (chromosomes arranged in pairs) and a representative metaphase spread image — meeting CAP Cytogenetics Checklist documentation requirements and enabling independent review.

Mosaicism Detection

Standard 20–30 cell analysis detects mosaicism at the 5–10% level; extended 50–100 cell analysis on request improves sensitivity to 1–2% — essential for prenatal diagnosis and post-transplant monitoring.

Oncology Prognostic Value

In leukemia and MDS, specific karyotypes (t(9;22) Ph+, inv(16), t(15;17), complex karyotype) directly determine prognosis and therapy selection per NCCN and ELN guidelines.

How It Works

Specimen Collection & Transport

Blood is collected in sodium-heparin or lithium-heparin tubes (NOT EDTA — chelates calcium required for mitosis). Prenatal specimens (amniotic fluid, CVS) are shipped at room temperature, never frozen. Bone marrow aspirates require the first pull (1–3 mL).

Cell Culture

Lymphocytes are stimulated with phytohaemagglutinin (PHA) for 72 hours; amniocytes and chorionic villi undergo flask or in-situ culture for 6–12 days; bone marrow is processed direct + overnight unstimulated. Colcemid arrests cells at metaphase.

Slide Preparation & GTG Banding

Cells are fixed (methanol/acetic acid), dropped onto slides, trypsin-digested, and stained with Giemsa to produce the characteristic G-band pattern. Minimum 400-band resolution (ACMG 2019); ≥550 bands for constitutional / prenatal per E-CA v1.01.

Microscopic Analysis

A board-certified cytogeneticist counts 20–30 metaphases and fully karyotypes at least 5 cells. Image capture via Zeiss Axio Imager.Z2 + Metafer. When mosaicism or a suspected abnormality is seen, additional cells (up to 100) are scored.

ISCN 2020 Reporting

Results are reported in International System for Human Cytogenomic Nomenclature (ISCN 2020) format, e.g. 47,XY,+21 or 46,XX,t(9;22)(q34.1;q11.2). The PDF report includes the formula, a representative karyogram image, and a metaphase photograph. Abnormal findings are reviewed by a second cytogeneticist before sign-out.

Clinical Correlation & Counseling

Results are interpreted in the context of the referral indication. Genetic counseling is included for all abnormal or uncertain findings; cascade testing recommendations are provided for balanced rearrangements.

Who should consider this test?

Couples with recurrent pregnancy loss (≥2 miscarriages) — to detect balanced translocations in either partner
Pregnancies with abnormal ultrasound findings, high-risk NIPT, or high-risk combined 1st-trimester screen (via amniocentesis or CVS)
Couples with unexplained infertility (to exclude balanced rearrangements, 47,XXY Klinefelter, 45,X/46,XX mosaicism)
Children with multiple congenital anomalies, unexplained intellectual disability, or ambiguous genitalia
Patients with suspected chromosomal syndromes (Down, Turner, Klinefelter, Edwards, Patau)
Patients with hematologic malignancies — leukemia / MDS / lymphoma — for diagnosis, prognosis, and MRD monitoring
Carriers of a known familial balanced translocation considering pregnancy

Conditions Screened

Autosomal aneuploidies — trisomy 21 (Down syndrome), trisomy 18 (Edwards), trisomy 13 (Patau)Sex-chromosome aneuploidies — 45,X (Turner), 47,XXY (Klinefelter), 47,XYY, 47,XXXBalanced reciprocal translocations (recurrent miscarriage, infertility)Robertsonian translocations (t(13;14), t(14;21), t(21;21))Inversions (pericentric, paracentric)Deletions and duplications ≥5–10 MbMarker chromosomes and ring chromosomesMosaic chromosomal disorders (true fetal mosaicism, confined placental mosaicism)Hematologic malignancy signatures — Philadelphia chromosome t(9;22), inv(16), t(8;21), t(15;17), complex karyotype, monosomy 7, del(5q)

Accuracy & Clinical Evidence

Test Accuracy

Conventional karyotyping detects chromosomal abnormalities ≥5–10 Mb in size with >99% accuracy for numerical aberrations. Mosaicism detection limit is approximately 5–10% with a standard 20–30 cell count, and can be improved to 1–2% on request by extended analysis (50–100 cells per ISCN 2020 §9.3).

Karyotype analysis has been the foundation of clinical cytogenetics since 1960. It is recommended by ACMG (Silva et al., Genet Med 2019), ACOG (Practice Bulletin 226 — prenatal aneuploidy), NCCN (leukemia/MDS guidelines), and ELN (AML risk stratification) as the standard for chromosomal analysis. Combined karyotype + chromosomal microarray (CMA) increases prenatal diagnostic yield by 6–10% over either test alone. In hematologic malignancies, karyotype is required for WHO classification and is included in ELN 2022 AML risk stratification.

For Healthcare Providers

Karyotype analysis at IMC Genomics is performed in an ISO 15189:2022–accredited cytogenetics laboratory following ISCN 2020 nomenclature, ACMG 2019 cytogenomics standards, E-CA General Guidelines v1.01, and CAP Cytogenetics Checklist requirements. Standard protocol: PHA-stimulated 72-hour lymphocyte culture (or tissue-appropriate protocol), colcemid arrest, hypotonic treatment, methanol/acetic-acid fixation, GTG banding. Minimum 20 cells counted and 5 cells fully karyotyped at ≥550-band resolution. Abnormal findings are double-reviewed before sign-out. FISH confirmation is available as a reflex for structural rearrangements; chromosomal microarray (CMA) is recommended for sub-microscopic (<5 Mb) findings. Every report delivers the ISCN formula, a full karyogram image, and a representative metaphase photograph. Turnaround: 10–14 business days standard; 7-day STAT available for prenatal and hematology-oncology referrals.

Important Limitations

Conventional karyotyping does not detect sub-microscopic deletions or duplications below ~5–10 Mb. Chromosomal microarray (CMA) or FISH is recommended for such findings.
Low-level mosaicism (<5–10%) may not be identified with standard 20–30 cell analysis. Extended cell-count analysis (50–100 cells) can be performed on request.
Uniparental disomy (UPD) is not detectable by karyotype — SNP microarray or methylation testing is required.
Single-nucleotide variants and small indels are not detected by karyotype — these require targeted sequencing, WES, or WGS.
Results depend on successful cell culture. Culture failure (<1% for blood, 2–5% for prenatal specimens) requires a fresh sample.
Maternal cell contamination in prenatal specimens is controlled by QC protocols but can occasionally limit interpretation.