Cytogenetics

Cytogenetics

Medical genetics plays an important role in all the aspects of medical practice: prevention, screening, diagnosis, and management. About 60% of the pregnancy losses, 2-3% of all the neonates and 50% of childhood deafness, blindness, mental retardation and 1 to 10 % of all the malignancies are directly due to genetic factors. Realizing the importance and need of genetic services in our country, Dr. Hema Purandarey founded the Center of Excellence in Cytogenetics (CoX Cytogenetics) formerly known as Centre for Genetic Health Care (CGHC) in 1981, a pioneer Genetic Centre in the country.
 
Dr. Hema Purandarey, Founder-Director eminently qualified for conducting the Centre, has been trained in all aspects of medical genetics at the most advanced centers/laboratories in the U.S.A., U.K. and Singapore. A team of Physicians adds to the credit of our center. Our skilled, trained and dedicated scientific officers and technical staff with the state of the art equipment ensure the output of quality work. The centre has experience of more than 60,000 genetic referrals.

Accreditations
 
The Center has
  • State of the art equipment
  • Range of genetic testing and counseling services
  • Qualified, experienced and dedicated team of MDs, PhDs and scientists
  •  All results interpreted by Qualified Medical Geneticists
  •  Minimum turn around time
 
Common Indications for Genetic Counseling and Testing
Preconception and Prenatal
  •  Consanguineous marriage
  • Members of a high risk ethnic group
  •  Maternal disease (eg. diabetes, PKU, epilepsy )
  • Single gene disorder (thalassemia, DMD)
  • Infertility or patients on IVF programme
  • Two or more pregnancy losses
  •  A previous child or a family H/O genetic / birth defect
  •  Positive triple test
  •  Abnormal ultrasound findings
  •  Women 35 years of age or above

Infants, Children, Adolescent and Adults
  •  Abnormal growth patterns / retardation
  • Ambiguous genitalia; early onset of puberty
  • Dysmorphic features, mental and growth retardation
  •  Metabolic disorder unexplained vomiting / convulsions...
  • Blindness or deafness
  • Primary and secondary amenorrhea
  • DNA parentage studies
  • Hemato-oncology

Cytogenetic Testing
Cytogenetic testing (Karyotyping) can be done on various body tissues in prenatal or postnatal life. This test is for the study of chromosome pattern. Any addition, deletion or structural change in the chromosomes leads to various abnormalities.

Blood
Karyotyping on peripheral blood sample is done for confirmation of clinical diagnosis, recurrence risk estimation and in cases with bad obstetric history, for various reproductive options. (Also refer the indication for genetic counseling).

Specimen: 2 ml whole blood in Sodium heparin vial. (Transport at room temperature).
 
Bone Marrow
Giving confirmation of diagnosis, prognosis and management. Most of the abnormalities are acquired and show characteristic changes in remissions / relapses.
 
Specimen: 0.2 ml to 0.5ml of bone marrow in a sterile sodium heparin vial. Include routine blood count and patient medication. In case sample is not adequate, an additional 2ml of peripheral blood in sterile sodium heparin vial is requested. (transport at room temperature)
 
Products of conception
In cases of early fetal loss 60% is due to chromosomal defects in the conceptus. Karyotyping of the products of conception assists in identifying the chromosomal factor and subsequent counseling and management for future pregnancies.
 
Specimen: Chorionic villi, or placental villi in tissue culture medium / balanced salt solution / normal saline or cord / cardiac blood in sterile sodium heparin vial. (Include ultrasound report; transport at room temperature).
 
Prenatal Diagnosis
The tissues generally studied for prenatal diagnosis are chorionic villi, amniotic fluid and cord blood. All prenatal fetal tissue samplings are done as outpatient procedures, under ultrasound guidance. The patient needs to be adequately counseled for the choice, safety, specificity and sensitivity of the test. An informed written consent is a prerequisite for the test. In-house facility for the obstetric procedure and sonography is available at the centre. The samples are also accepted through centers licensed for fetal tissue sampling. Prior discussion with CoX-Cytogenetics before sampling is important.
 
For indications refer to Genetic Counseling Section.
 
CHORIONIC VILLI
The tissue sampling is done by transcervical or transabdominal route between 10-12 weeks gestation. At a later gestation, placental biopsy (late CVS) is offered. (For enzyme assays and molecular diagnosis, carrier testing in the couple and/or mutation analysis in the affected child is essential. Do not send these samples unless the case is thoroughly discussed with us).
 
Specimen: 20mg of chorionic villi in tissue culture media. (Transport at room temperature)
 
AMNIOTIC FLUID
Obtained by amniocentesis between 15-18 weeks gestation.
 
Specimen: 20ml of amniotic fluid in provided sterile tubes. (Transport at room temperature)
 
CORD BLOOD
This is indicated for rapid karyotyping during second and third trimester of pregnancy with abnormal ultrasound findings or for confirmation of karyotype of CVS or amniotic fluid.
 
Specimen: 2ml cord blood in sodium heparinized vial. Verify at source that the blood is of fetal and not maternal origin. (Transport at room temperature)
 
Genetic Screening
Genetic screening helps to identify an individual who could be at risk for a genetic disorder or a birth defect, in prenatal or postnatal period. eg Thalassemia, Neural tube defect, Huntington's disease, etc. Screening at times needs to be supplemented by diagnostic tests; early intervention helps in patient management. We offer pre-test counseling, interpretation and post-test counseling in these cases.
 
Prenatal Screening
Different strategies are being devised to screen populations of pregnant mothers to help identify those at potential risk of a chromosomally abnormal fetus, targeting them for invasive diagnostic procedures. These procedures include:
  • Ultrasound screening for fetal chromosomal disease and identification of marker. Fetuses with positive ultrasound markers should be considered for prenatal cytogenetic diagnosis. Fetal echocardiography is an important tool for picking up congenital heart diseases (18-20 weeks), and is important for management of CHDs.
  • Maternal serum screening using biochemical markers
 
Triple Test
Screening test for Neural tube defects and Down syndrome
A screening test based on the combination of age, MSAFP, hCG and UE3 picks up fetuses at risk for trisomy 21 and 18. First trimester screening is now possible with an additional marker PAPP-A. Elevated levels of AFP indicate high risk for neural tube defect.
Triple tests provide RISK estimation and are not diagnostic. A screen negative result does not exclude the possibility of Down syndrome or a neural tube defect, because screening does not detect all affected pregnancies. Screen positive patients should be considered for chorionic villi and amniocentesis.
 
Specimen: 2ml maternal blood. (Information required: maternal age, LMP, assisted or normal conception, ultrasound biometry and number of fetuses, diabetic status and weight of the patient; transport at room temperature).
 
Neonatal screening
Effective neonatal screening improves the quality of life. The disorders covered under this screening are- Congenital Hypothyroidism, Congenital Adrenal Hyperplasia (CAH), Phenylketonuria (PKU), Galactosemia, Biotinidase deficiency, Maple Syrup Urine Disease (MSUD), G6PD deficiency and Cystic Fibrosis. Done on a drop of blood by heel puncture on special filter paper (Spot test) or 1ml heparinised blood in a sterile test tube.
Prior discussion with the centre is necessary.
 
Biochemical Studies and Molecular studies
These tests are done in conjunction with the specialized centers. For these studies couples are counseled, samples are taken and forwarded, if required, to the specialized centers nationally and internationally.
These studies are used in the diagnosis of inborn errors of metabolism. They can be performed on blood, urine or body fluids /tissues as per the clinical picture (phenotype) or the clinical impression of the physician.
Inherited metabolic disorders can be inherited as an autosomal recessive, dominant or a sex linked disorder. The diagnosis in an index case provides the basis for further management, recurrence risk estimation and prevention. The clinical presentation of such diseases is often diverse and many present in the neonatal period. Some of the clinical indications include mental retardation, dysmorphology, myopathies, cardiomyopathies and storage disorders.
 
Requisite: Prior discussion is necessary to decide the specific test. List is available on request, done in association with Willink Biochemical Genetics Unit. UK
 
Fluorescent in Situ Hybridization (FISH)
FISH technique is used to detect numerical as well as minor structural rearrangements on all the body tissues as per the indication. For this prior discussion with the lab is essential. Currently it is available for fetal aneuploidy, microdeletion syndromes and oncology. This is done in association with Prof. Dr. Ingo Hansmann Institute for Human Genetics, Halle, Germany).  The most common are blood for rapid syndrome identification, bone marrow for hematological malignancies, classification for diagnosis, prognosis and management and amniotic fluid and chorionic villi for rapid prenatal diagnosis of fetal aneuploidy.
 
Genotoxicity Studies
In-vivo mutagen induced chromosome damage
Cytogenetic studies can be used to monitor populations for a range of environmental and occupational clastogens and mutagens and for radiation, can provide an estimate of individual dose. Studies include structural chromosome aberrations.
  • Sister chromatid exchanges
  • Micronuclear tests
  • Chromosome breaks
 Sample: 5ml of peripheral blood in sodium heparin vial.
 
Genetics of Organ System Diseases
Genetic testing and counseling besides being important for obstetric, gynecological, pediatric and oncological practice is also of great importance in case of organ system diseases.
 
Other Medical Disciplines
  • Cardiovascular diseases (congenital heart disease, familial hypercholesteremia)
  • Endocrine diseases (congenital hypothyroidism, adrenogenital syndrome)
  • Gastrointestinal diseases (hereditary pancreatitis, adenosis polyposis)
  • Hematological disorders (Blooms syndrome, ataxia telangiectasia, hereditary anemias, hemoglobinopathies)
  • Diseases of the skeletal muscles (spinal muscular atrophy, DMD, Becker's muscular dystrophy)
  • Neurological diseases (Friedrich's ataxia, Huntington's disease, epilepsy, neurofibromatosis, tuberous sclerosis)
  • Eye diseases (congenital cataract, retinoblastoma, retinitis pigmentosa)
  • Hereditary hearing loss (acoustic neuroma, prelingual hearing loss)
  • Renal disorders (polycystic kidney disease, chronic heredity nephritis)
  • Respiratory system disorders (cystic fibrosis, congenital bronchiectasis)
  • Heritable skeletal dysplasias (achondroplasias, osteogenesis imperfecta)
  • Disorders of skin (epidermolysis bullosa, congenital ichtyosis)
  • Hereditary defects of teeth and oral structures (dentinogenesis imperfecta)
FAQ
 
What is genetic testing?
Genetic testing is the study of inherited material or products of metabolism to rule out / identify the cause of a hereditary disorder. It is possible in all the age groups - from fetal life to the adult individual. It is "once in a lifetime" test.
 
Why is genetic testing important? What is the burden of genetic disorders?
Genetic testing confirms a clinical diagnosis. It identifies the basic cause underlying a disease, assists in its management and opens up new options and reproductive choices.
  • 50% of the pregnancy losses are associated with a chromosomal abnormality
  • 2% of the newborns have a single gene disorder or a chromosomal abnormality
  • 50% of the mental retardation, childhood blindness or deafness are the result, of genetic defects
  • 1-10% of the cancer patients show chromosomal aberrations
  • 5% of the adult disorders by the age of 25 have genetic factors as a major cause
 
What are the various branches of Genetic Testing?
  • Study of chromosomes - Cytogenetics
  • Study of metabolic products - Biochemical Genetics
  • Study of DNA - Molecular Genetics
  • Genetic Counseling - An important and a cost effective test where a medical 'geneticist with the help of a detailed history and relevant investigation reports can offer various options, which are open to the concerned individual/couple. This interactive session with the patient will aid further planning /selection of tests or rehabilitation.
 
What are the tissues that can be studied?
  • Peripheral blood - A routine karyotype is most often done on the peripheral blood for the individual’s chromosomal characteristics. The important indications are: bad obstetric history, unexplained infertility in males and females, males with oligozoospermia, primary and secondary amenorrhea, sexual infantilism in males and females, patients with dysmorphic features mental retardation, hematological disorders.
  • Bone marrow - for hematological malignancies
  • Amniotic fluid, chorionic villi, cord blood - for prenatal diagnosis
  • Products of conception for abortus studies.
 
What are the pre-requisites?
  • Fasting is not required
  • Results of mailed samples are equally reliable in most of the cases
  • Samples should be transported at ambient temperature
  • Pre-test instructions and counseling is required in prenatal cases
  • Post-test counseling, after the reports are ready, is offered by way of interpretation
Additional personal counseling may be required and is suggested whenever necessary
 
How is the sample processed?
Processing of the samples involves the following steps:
  • Initiation of the culture by using culture media and nutrients for cell growth
  • Incubation for maturation of the cell and accumulation of mitotic cells
  • Harvesting for termination of culture
  • Slide preparation, staining and banding
  • Analysis and interpretation
 
What is the responsibility of the collection centre?
  • Identify the test recommended by the referring physician
  • Read any relevant instructions before collecting the specimen
  • Include clinical history, label the sample appropriately including time and date of collection and forward it to the main laboratory
  • Do not accept samples if they are unsuitable or inappropriately collected 
  • If the sample is inadequate in quantity or quality for evaluation, a request for a repeat sample will be made at no extra cost to the patient