The following information has been taken, without
alteration, from the Genetic Testing web page of The
Doctors Laboratory, our sister organisation in the
UK. Please contact us to
determine specific local requirements, hours and contact numbers
for genetic testing at MLP.
From The Doctors Laboratory:
TDL Genetics is a consultant-led service which is able to provide
extensive expertise in the testing, diagnosis and genetic
counselling of inherited disorders. Genetic tests are performed on
DNA for molecular genetic analysis and on whole chromosomes for
cytogenetic analysis. Some tests are part of profiles that can be
linked with assays from other TDL disciplines, such as biochemistry
and haematology, to give more comprehensive results for the
Genetic tests are available for:
- Prenatal diagnosis and rapid trisomy screening by
- Carrier screening
- Newborn chromosome analysis
- Confirmation of symptomatic individuals and pre-symptomatic
- Genetic variation that influences risk of disease
- Identity studies (paternity, zygosity, tissue typing)
- Fertility studies
Genetic testing is sometimes complex and tests will vary in their
ability to detect mutations or to detect all patients who have, or
will develop, the disease. Some tests are diagnostic for a
condition, others are indicative or are associated with an altered
risk for a condition. Results can affect the lives of individuals
and have implications for their family, for insurance and
employment. Where testing will predict the inheritance of a disease
in a healthy person counselling and consent are mandatory. For
these tests, please complete the Genetic Request form at the back
of the guide (including informed consent). Our service provides
result interpretation and risk assessment to patients and their
family members. Genetic counselling can be arranged by TDL's
Consultant Clinical Geneticist.
To meet the increasing range and complexity of genetic testing we
have developed an excellent
collaboration with other specialist laboratories. Tests marked GENE
are sent to these laboratories
within our network and have a fixed price.
|Specimen Receipt at The Doctors Laboratory is 24 hours a
Specifically, TDL Genetics results service is available
Monday to Friday 8.30am - 5.30pm with the laboratory also
for processing of samples on Saturdays from 9.00am - 1.00pm.
Samples should be fresh and in good condition (e.g. not clotted if
EDTA whole blood is required) otherwise testing may be adversely
affected and another sample may be required. Small DNA samples are
stored routinely for one year, larger DNA samples can be stored by
Instructions for transportation, sample labelling, and the
completion of request forms can be attained from our Customer
Support Department by free-phoning 1800 303 349.
If you do not find the test you require or need more information
and advice please telephone the laboratory on 1800 303 349 where
our customer support department will be able to assist you.
TDL GENETICS External
- Constitutional Cytogenetics
- Molecular Genetics
- Histocompatibility and Immunogenetics (includes
Haemochromatosis, HLA B27 and HLA identification)
- Y chromosome microdeletions
* For full information about Amnio PCR testing, see www.amniopcr.com.
The importance of Clinical Details
Clinical details are very important when providing genetic
analysis. The more clinical information that is available (e.g.
details of ultrasound information, phenotypic features or family
history) the better the service we can provide. Failure to provide
this information for cytogenetic studies may result in an
Cytogenetic analysis is performed according to the Professional
Guidelines for the Association of Clinical
Cytogeneticists and the recommendations provided are dependent on
the clinical indications given for
Clinical details inform the investigation at all stages:
- Prior to analysis, clinical details may indicate, for example,
that specialist procedures such as chromosome breakage or leukaemic
studies are required, which must be referred to a specialist
- During analysis they may indicate that extra cells should be
screened to investigate the possibility of mosaicism, for example
in a diagnosis of suspected Turner syndrome, or that particular
chromosomes must be targeted for high-resolution study, for example
chromosome 8 in suspected Langer-Giedion syndrome.
- When the analysis has been completed they may help to provide
an accurate interpretation of the findings and in some instances
prompt further investigations, for example FISH or molecular
When clinical details are not available a routine analysis will
be performed and a conditional report issued.
Clinical details can be extremely important for clinical
interpretation of a molecular genetic test.
For example, the clinical comments accompanying a cystic fibrosis
screening report will vary depending
on whether the patient is a potential gamete donor or a person
exhibiting a cystic fibrosis phenotype.
Similarly, the interpretative comment accompanying Factor II and V
studies may vary depending on
whether the investigation is prompted by a history of recurrent
miscarriage or the need to determine a
It may also be crucial, where a mutation has already been shown to
be segregating in a family, to be
provided with information concerning the mutation and a family
pedigree to ensure the correct analysis
is performed and reliable risk figures calculated.
Notes for Cytogenetics
As cytogenetic studies require living cells, please ensure that
samples reach the laboratory quickly. If a delay
before despatch is unavoidable, samples may be stored in a
refrigerator (4°C) but they must not be
On completion of analyses, fixed cell suspensions are stored for
a minimum of three months and are available
for additional follow-up studies (for example, FISH), if
Requesting additional tests
Any further tests not requested at the time of sample receipt must
be requested within:
- 2 weeks for DNA testing
- 2 weeks for cell culture testing
- 3 months for FISH testing
Samples can be stored for longer periods if specifically
requested at the time of sample receipt.
Postnatal Diagnosis (Blood Culture)
Reasons for analysis: Chromosome studies are
requested where problems that may have a cytogenetic
basis are suspected, e.g. babies with birth defects; children with
developmental delay and physical handicaps,
or adults with fertility problems. Additionally, prospective gamete
donors are screened to detect carriers of
balanced chromosome rearrangements.
Sample requirements: Lithium heparin whole blood
specimens are required - gently mixed to prevent clotting
and must not be frozen. Sample volumes may be reduced for children
(2-4ml) and neonates (1-2ml).
Turnaround time: The usual turnaround time is 2-3 weeks
however the laboratory will endeavour to respond
to urgent requests. Where a major trisomy is suspected, a rapid PCR
screen may be performed to provide an
urgent provisional result.
a) Rarely, blood samples fail to culture
b) The culture may yield chromosomes of
insufficient quality. This will be indicated on the report and a
repeat study suggested;
c) The laboratory should be informed if the
patient has recently received a blood transfusion.
Leukaemic Studies (Bone Marrow)
Sample requirements: 5-10ml bone marrow in
preservative free heparin and RPMI medium. This can be supplied by
Clinical information: Please complete the
Leukaemic Studies Request form at the back of the laboratory guide,
including WBC, reason for referral, stages of disease/treatment and
analysis required i.e. karyotype and/or FISH.
Reasons for analysis: Chromosome studies are
requested where pregnancies are identified as being at risk
of a cytogenetic abnormality e.g. advanced maternal age; positive
maternal serum screening; fetal abnormalities found on ultrasound;
or where a parent is a known carrier of a chromosome anomaly.
a) amniotic fluid - 10ml+ in a plain sterile,
leak-proof container. Suitable containers can be provided by the
laboratory. The specimen must not be frozen.
b) chorionic villus - 5mg+ in sterile transport
medium. Suitable containers containing medium can be provided by
the laboratory. The specimen must not be
c) fetal blood - 1-2ml LITHIUM HEPARIN
whole blood, gently mixed to prevent clotting.
The specimen must not be frozen.
Turnaround time: This is dependant on the rate of cell
growth, however, the usual turnaround time is approximately two
weeks. Fetal blood results will usually be reported within 7
a) Maternal contamination, and mosaicism may
complicate the analysis and may lead to the suggestion that a
second invasive test is performed.
b) Rarely, cultures fail to grow (overall
c) Very small chromosome abnormalities may not be
detected (this is why the phrase 'No trisomies or major chromosome
abnormalites detected...' is used in our reports).
Reasons for analysis: Fibroblast cultures may
be used in addition to blood cultures, for example where
specific mosaicism is suspected, or where blood samples cannot be
obtained. Analysis may be requested for early spontaneous
miscarriages, stillbirths, or to confirm a prenatal
Sample requirements: All specimens should be
placed in a sterile container, preferably containing
medium. This can be supplied by the laboratory. Sterile normal
saline can be used if transport medium is
not available. Samples must not be placed in
formaldehyde or other preservative and must not be
Turnaround time: This is dependant on the rate of cell
growth, however, the usual turnaround time is
approximately 4 weeks.
a) Material from miscarriages has a relatively
high culture failure rate (around 20%)
b) If no villus or fetal parts are identified in
supposedly POC material and a normal female chromosome result is
found, this may indicate that maternal tissue has been cultured
(this will be noted on our report)
c) Disposal of material from miscarriages will be
by incineration. Other arrangements can be made if requested at the
time of sample receipt
Fluorescence In Situ Hybridisation (FISH)
Where FISH studies for specific microdeletion syndromes are
required this must be indicated on the request form.
Note: FISH studies for a prenatal aneuploidy screen have now been
superceded in our laboratory by multiplex-PCR technology and
subtelomeric screens are now performed by an MLPA assay.