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FISH(Fluorescence In Situ Hybridization)

Fluorescence in situ hybridization (FISH) is a powerful technique used in the detection of chromosomal abnormalities. The high sensitivity and specificity of FISH and the speed with which the assays can be performed have made FISH a pivotal cytogenetic technique that has provided significant advances in both the research and diagnosis including cancer cytogenetics, prenatal screening of chromosomal aberrations, molecular pathology and developmental molecular biology.

G-banded karyotyping is the most common approach for the detection of genomic alterations. However, despite its indisputable success, this tool has limited resolution, usually being unable to detect genomic changes of less than 5 Mb. In addition, most rearrangements of the ends of the chromosomes (telomere or sub-telomere) are too small to be detected using traditional banding technique. These limitations of conventional chromosome analysis have been overcome by FISH (Fluorescence In Situ Hybridization). The ability of FISH to detect cryptic chromosomal rearrangements exceeds the resolution of any form of cytogenetic banding techniques. However, conventional FISH does not allow a comprehensive evaluation of the whole genome. Thus, FISH provides a high-resolution analysis of only targeted locations. The role of FISH for the rapid detection of various clinically suspected microdeletion syndromes.

FISH analysis may also be performed on additional specimen types:

  • Bone marrow/blood/lymph nodes to evaluate leukemia/lymphoma changes
  • Formalin-fixed, paraffin-embedded tissue
  • Frozen tissue sections
  • Direct smears from blood or bone marrow
  • Buccal smears

Note: FISH results may provide diagnostic and/or prognostic information; however, diagnostic or patient management decisions should be made in the context of clinical symptoms.

FISH as a tool for rapid aneuploidy screening (RAS) of high risk pregnancies, the most frequent fetal chromosomal abnormalities involve the autosomes 21, 18, 13, and sex chromosomes X and Y. Aneuploidy or alterations in copy number of these chromosomes, including trisomy 21 (Down syndrome), trisomy 18 (Edwards’ syndrome), trisomy 13 (Patau’s syndrome), 45, X (Turner’s syndrome), and 47, XXY (Klinefelter’s syndrome) account for 80% of clinically significant chromosomal abnormalities diagnosed in the prenatal period

Sample Type: Amniocentesis, CVS, POC & Blood

The applications of FISH in oncology broadened to include more genetic diseases, hematologic malignancies, and solid tumors. For example, FISH detection of BCR/ABL1 translocation, HER2 amplification, and ALK rearrangement is critical for guiding targeted therapy in chronic myeloid leukemia, breast cancer and lung adenocarcinoma, respectively. Hence, FISH tests have been recognized as vital components of personalized medicine.

Sample Type: Peripheral Blood, Cord Blood, Bone marrow, Paraffin-embedded tissue.

The microdeletion syndrome is characterized by hemizygous microdeletion (less than 5 MB) of chromosomes in which one or more genes are lost. It is mostly spontaneous, and is reported to occur in approximately 5 per cent of patients with unexplained mental retardation. This is frequently associated with multiple congenital anomalies and developmental delay.

The known microdeletion syndromes are :

  1. DiGeorge(22q11.2)
  2. Prader-Willi/Angelman (15q11-13)
  3. William(7q11.23)
  4. Smith-Magenis(17p11.2)
  5. Cri-du-Chat(5p15.2)
  6. Miller-Dieker(17p13.3). etc.,

Sample Type: Amniotic fluid, CVS, POC & Blood

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