CYTOGENETICS

Cytogenetics is a branch of genetics that studies the number and structure of human chromosomes, searching for balanced or unbalanced chromosomal rearrangements. These rearrangements may be present as translocations between two or more chromosomes, inversion within one chromosome, insertion, deletion or duplication of one segment of a chromosome or gain or loss of a whole chromosome (aneuploidy).

Some chromosomal rearrangements are present from birth and in every cell of the body, these are called constitutional abnormalities. Another group of chromosomal abnormalities, which are common in neoplastic and cancerous cells are acquired chromosomal aberrations. It is possible to prepare chromosome samples starting from any tissue (or suspension of mitotic cells) provided that appropriate methods are used for the type of cell to be examined.

An organized profile of a person’s chromosomes classified on the basis of both chromosome number and morphology, is called karyotype. Metaphase cells are required and virtually any population of dividing cells could be used.

The karyotype helps Cytogeneticist to identify chromosomal alterations that may result in any genetic disorder. Thus cytogenetics is a supportive test that helps the clinicians of different specialities in diagnosis and prognosis of patients with various chromosomal abnormalities, which are studied by Karyotyping and Fluorescence in-situ hybridization [FISH].

AJC performs these diagnostic tests in prenatal, postnatal disorders and cancer.
 

PRENATAL CYTOGENETIC ANALYSIS

is performed, preferably after genetic counseling, on any viable tissue, such as chorionic villi (CVS), amniotic fluid, cord blood (POC), Products of conception and placental biopsy in case of:

• Advanced maternal age:
  Chromosomal aberrations can occur in children born to mothers of any age group but the risk of a woman‘s giving birth to a child with trisomy increases with increasing age of conception (commonly over 35 years old).
• Abnormal ultrasound findings:
  Some ultrasound findings can indicate a chromosomal change in the fetus and it is advisable to seek chromosomal analysis and genetic counseling to establish further prenatal diagnostic methods.
• Chromosomal aberrations in a previous child:
  If a couple already has a child with a trisomy or structural chromosomal anomaly, the probability of having another child affected is increased.
• Chromosomal structure changes in the parents:
  Healthy people can carry changes in their chromosomal structure that have no consequences for themselves, but they have an increased risk to have offspring with unbalanced rearrangements (translocations or aneuplodies). If a person is a carrier of a balanced chromosomal rearrangement it is advisable to seek genetic counseling to discuss further prenatal diagnostic options.
• Results of abnormal biochemical tests
  Certain results in the maternal serum screening tests performed in the first pregnancy trimester can indicate that a chromosomal aberration may be present. To elucidate a positive screening test, for diagnosis is necessary to perform a fetal karyotype, analyzing the chromosomes of the fetus.
• Birth of a child with multiple anomalies
  Multiple congenital anomalies are often the result of chromosomal aberrations, those being identified in approximately 30% of all live-born children with deformities and in 5% of stillborn children. Prenatal diagnosis is indicated whenever a previous child was identified with a chromosomal aberration.
• Repeated miscarriages
  Habitual spontaneous abortions can indicate a fetus has a chromosomal aberration. 60% of first trimester miscarriages are due to a fetal chromosomal abnormality. If a chromosomal change was present in previous miscarriages, the risk is increased for subsequent pregnancies. Repeated miscarriages can be a sign of chromosomal changes in one of the parents it is advisable to seek chromosomal analysis and genetic counseling before new pregnancy.

Note: If requested, additional cell cultures can be set-up for molecular diagnostic for other prenatal testing, such as fetal antigen or DNA testing for other suspected genetic disorders.

POSTNATAL CYTOGENETIC ANALYSIS

Is performed preferably, after genetic counseling, using peripheral blood in cases of:

• Multiple congenital abnormalities
• Dysmorphism
• Developmental delay
• Mental retardation
• Ambiguous genitalia
• Suspected deletion/microdeletion
• Duplication syndrome
•  Short stature
• Abnormal secondary sexual characteristics
• Secondary amenorrhea or premature meno-pause
• X-linked recessive condition in a female
• Features of a chromosome breakage syndrome, or other syndrome with specific cytogenetic findings
• Parents with prenatal diagnosis detection of a chromosome abnormality or unusual variant
• Couples with stillbirths with a suspected chromosome abnormality
• Multiple miscarriages or infertility
• Monitoring after bone marrow transplantation (e.g. other-sex donor in treatment of Thalassemia)
• Environmental exposure to known mutagens or carcinogens

 CANCER CYTOGENETIC ANALYSIS
 Is performed using bone marrow aspiration, leukemic blood, fine needle aspirates (FNA) and biopsy in cases of patients with leukemia, lymphoma and solid tumors:

The chromosomal changes in tumor cells are unevenly distributed throughout the genome, and specific chromosome regions and genes seem to be preferentially involved in the different neoplasia. Chromosome analysis for hematological disorders of leukemic blood cells are performed to identify specific chromosome rearrangements. These rearrangements in neoplastic cells are often correlated to specific types of leukemia or myelodysplasias. The identification of genes involved in neoplasia provides a better understanding of the disease processes.

MOLECULAR CYTOGENETIC ANALYSIS

FLUORESCENCE IN-SITU HYBRIDIZATION (FISH)

FISH is a molecular cytogenetic technique that enables the analysis of disease specific abnormalities as well as the chromosomal localization of specific DNA sequences by which an assessment is made for the presence, absence, relative positioning and/or the copy number of specific DNA segments by fluorescence microscopy. It is offered for the detection of cryptic rearrangements, microdeletion, marker chromosome, and aneuploidy identification.

It may be utilized to address specific, focused clinical questions and is provided for a variety of clinical applications, including the assessment of both constitutional and acquired chromosomal aberrations. Depending upon the application, FISH can be applied to interphase nuclei / metaphase. Cells obtained from various samples for the effective and rapid detection or identification of chromosomal / gene rearrangements.

Thus FISH results are used as an aid in the prenatal, postnatal and cancer diagnosis of numerical and structural chromosomal abnormalities using different types of FISH probes such as unique sequence probes: (sometimes referred to as LSI or “Locus-Specific Identifier probes) Fusion probes, breakapart and enumeration probes.

The laboratory methodologies employed vary with the type of study requested therefore, it is imperative that the clinical reason for the test be provided at the time of sample submission.

FISH IN PRENATAL DIAGNOSIS USING AMNIOTIC FLUID 

• Cells from amniotic fluid (AF) are cultured and analyzed using the FISH method, a technique that provides shorter turnaround times and a more accurate interpretation in cases of mosaics for an abnormal cell line.
   
• Prenatal interphase aneuploidy screening for chromosomes 13, 18, 21, X and Y (Aneuvysion) can be performed by FISH for those specimens meeting the minimum AF volume requirement.

FISH FOR NEOPLASTIC DISORDERS is suggested for the following indications:

• To identify various translocations, deletions, and chromosomal gains, as well as other rearrangements associated with specific hematopoietic disorders.
• To monitor course of treatment of leukemia and lymphoma and to confirm remission or relapse status.

OUR MERITS/Proficiency/Features

Accuracy, quality, reliable turnaround times and a highly qualified staff are all significant features of Cytogenetics Laboratory.

Staff are highly skilled and achieve outstanding culture success rates. We attain greater than 99% culture success rates for amniocentesis, CVS and blood samples and nearly 85% culture success rate for POC, using our proprietary culture media. We are the only laboratory in Bahrain which is capable of performing prenatal and cancer cytogenetics and our test results are available through an LIS interface, phoned, faxed and/or mailed upon completion of analysis.

FISH (FLUORESCENCE IN SITU HYBRIDIZATION) FOR CONSTITUTIONAL STUDIES

FISH (FLUORESCENCE IN SITU HYBRIDIZATION) FOR CANCER STUDIES

​For more information please contact:

Phone: 17 237 304
E-mail: cytogentics@agu.edu.bh 

For Cytogenetics tests Request Form, please click here.