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The first 25 slides, exactly as they appear. The full deck has 96 content slides.
Radiology
Prenatal Genetic Testing A Pragmatic Approach
Built from Obstetric Imaging
What’s inside
6 sections · 96 slides
Overview
- The one idea to hold on to
- Why this has changed so fast
- Routes for testing a pregnancy
- What this topic covers
Screening versus diagnosis
Two tests with two different promises
- What screening actually is
- What a diagnostic test is
- The two side by side
- From whole population to an answer
- The disease has to sit in a sweet spot
- Screening you already know
- The four things a screening test must satisfy
- Screening is a second line of defence
- Principles of screening, part one
- Principles of screening, part two
- Theory versus practice
- Which tests are screening and which are diagnostic
- Typical Tests Used for Fetal Screening or Diagnosis
- Typical Tests Used for Fetal Screening or Diagnosis (continued)
- Screening and diagnostic tests on one page
- How Down syndrome screening used to be done
- up to 99%
- Combined first trimester screening: the ingredients
- Combined screening: what comes out
- An increased neck fluid says more than trisomy risk
- Counselling before screening is the hard part
- The emotional cost is part of the test
- Diagnostic tests need fetal material
- Taking a sample of amniotic fluid
- What placental tissue looks like next to womb lining
- Consent is not paperwork
- Who gets offered what
- What each genetic test on fetal material is for
- Genetic tests from fetal material: what each test is for
- Genetic tests from fetal material: practical limits
- Genetic tests from fetal material on one page
Judging a screening test
Detection rate, false positives and predictive value
- Why the numbers matter
- Detection rate: how many of the affected you catch
- Detection rate: a worked example
- Where the four kinds of result come from
- Where a cut-off creates false positives and false negatives
- The four results a screening test can give
- False positives: the price of catching cases
- The false-positive rate tells you the workload
- 85%
- Reading '85% DR for 5% FPR'
- >99%
- So is NIPT simply the better test?
- Positive predictive value: what a positive means for her
- The same word 'positive', two very different meanings
- Why you still cannot skip the invasive test
The genetic toolbox
What each laboratory test can and cannot see
- From whole chromosomes down to single letters
- Reading chromosomes with glowing probes
- What FISH is used for in practice
- What FISH cannot see
- How a fluorescent probe finds its gene
- Counting chromosomes by copying DNA
- Reading the peaks
- Limits of QF-PCR, and where FISH wins
- Two fast tests, side by side
- Karyotyping without a microscope
- Technique one: comparing patient with control
- Technique two: counting alleles
- How fine, and what it still misses
- A microarray slide in the hand
- Looking at chromosomes down a microscope
- Why karyotyping takes days, not hours
- Three copies of chromosome 21 in a karyotype
- Reading DNA letter by letter
- Spotting missing or duplicated exons
- Sequencing many genes at once
- Exome or whole genome?
- When to reach for genome sequencing
Testing the mother's blood
Cell-free fetal DNA and what it can honestly tell you
- A genetic test that needs only a blood draw
- Where the fetal DNA actually comes from
- Fetal fraction: how much of the signal is the baby's
- Standard NIPT and genome-wide NIPT
- What genome-wide NIPT can pick up
- Why a positive NIPT is still only a screen
- The honest position on NIPT
Putting it to work in clinic
Who is actually at risk, and which test to order first
- The old risk labels have been retired
- Risks that come from the family history
- The healthy carrier problem
- 1–2%
- Reading those recurrence numbers
- Two kinds of ultrasound finding
- Hard markers and soft markers
- The special case of increased neck fluid
- Increased neck fluid plus a heart defect
- Short bones and short ribs
- When the scan is abnormal but nothing fits
- What to carry away, part one
- What to carry away, part two
- Acknowledgment
- References
- References (continued)
- Obstetric Imaging: Fetal Diagnosis and Care, 2nd Edition