Pre-implantation screen/policy Flashcards
Define diagnostic testing, what information may it provide?
Confirms a diagnosis in an affected person, may provide prognostic info
Define predictive testing. What are the 3 types?
Testing of unaffected individuals, usually in the absence of corroborating evidence.
Pre-symptomatic - determine whether/not a person will develop disease
Carrier - determine whether person could have affected offspring
Prenatal/pre-implantation - predict whether a child will be born with/develop disease
Define screening testing
Testing of individuals at population-level risk of disease
Define somatic testing
Testing of tumour tissue (not germline testing)
Define pharmacogenetic testing
Drug metabolism/toxicity
What are some considerations of sampling?
- purpose of testing
- biochemistry vs RNA vs RNA testing
- risk to patient (invasiveness, bleeding risk)
- abundance of sample
What is peripheral (whole) blood sample?
Where is it extracted from?
Why is it a preferred source of DNA testing?
DNA found in nucleated cells.
Extracted from white blood cells.
Because it is plentiful, easy access and minimally invasive
What is buccal cells, urine and skin samples and when are they used? What does it compare?
An alternative to blood used if difficult to get blood for some reason. Collected via swab of cheek, morning urine or biopsy. For comparison of tumour DNA to constitutional DNA.
What is chorionic villus sampling and amniocentesis and when is it used?
Chorionic villus sampling: extraembryonic tissue (placenta) at 11-14 weeks
Amniocentesis sampling: foetal cells from amniotic fluid at 15-18 weeks
What are the risks of chorionic villus sampling and amniocentesis?
- Bleeding and infection
- loss of pregnancy
- potential for incorrect results due to contamination with maternal cells
What is cell free DNA sample and when is it used?
DNA not contained by membranes but floating free in circulation can be isolated from peripheral blood. Used for non-invasive prenatal testing (NIPT) - as early as 5 weeks
How to choose which test to use?
- Which change trying to be detected?
- size (molecular or cytogenetic)
- where it occurs (single or multiple loci)
- type of change (sequence, CN, methylation)
- volume of samples being tested
- purpose of testing (known or unknown mutation)
What is targeted and untargeted testing?
Targeted testing: specific alleles or CNVs are tested for the mutation being looked for is there no not
Untargeted testing: whole or multiple genes, whole genome; more than one disease variant may be found, but which ones are causative?
Define pathogenicity
Whether the variant is able to cause the disease
What is the 5 tier classification system of pathogenity?
Class 1 - benign Class 2 - likely benign Class 3 - Uncertain significance Class 4 - likely pathogenic Class 5 - Pathogenic