Genetic counseling: Abnormal Triple Screen and Family History of PKD
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Abnormal Triple Screen and Family History of PKD
Introduction
Edit
- What have you been told about why you are here today?
- We want to discus the triple screen results and what they really mean
- We want to get a family history to assess for any other risks related to pregnancy
- We want to talk about the different testing options available to you.
Family history update (at beginning depending on level of anxiety)Edit
- Who in the family has been diagnosed with PKD?
- What age were they diagnosed?
- Do any of your family members have high blood pressure?
- Do any other people in your family have kidney problems?
Edit
- Do you see a doctor regularly?
- Are you currently on any medication?
- Have you had a renal ultrasound or CT scan?
- Have you experienced any urinary tract infections?
- Have you had high blood pressure?
- Have you experienced any pain in your stomach or back?
Pregnancy HistoryEdit
- Verify dates
- Any exposures?
- Any cig/alcohol/drug use?
- Any increase in blood pressure?
- Any ultrasounds so far? When is the next one scheduled?
Triple screen info.Edit
- The test itself
- Best results at 16-18 weeks gestation (can be done from 15-22 weeks)
- Tests mother's blood
- NOT diagnostic...simply an indication for additional testing
- Uses three markers to determine indicators for certain fetal problems
- The three markers
- produced by the fetus and the placenta
- Alpha feto protein(AFP)
- Human chorionic gonadotrophin (HcG)
- Most sensitive risk factor for DS
- Greater than 2.5 MOM indicated risk for DS
- Estriol
- Median of 0.5 MOM in Trisomy 18
Interpreting ResultsEdit
- Certain combinations of levels give us an indication for possible chromosomal abnormalities
- Standard results AFP =1.0, hCG =1.0, uE3 =1.0
- High AFP >2.0 or 2.5 MoM indicates ONTD ( see above)
- High hCG >2.5 MoM indicates Down Syndrome(see above)
- Low uE3 >0.8 MoM indicates Trisomy 18(see above)
- Low AFP, high hCG, low uE3 indicates Down Syndrome
- Low AFP(>0.75 MoM), low hCG(<0.55 MoM), low uE3(<0.60 MoM) indicates Trisomy 18
Patient's resultsEdit
- AFP = , HcG= , UE3=
- Increased risk for Down syndrome
Explain chromosomes and what Down syndrome isEdit
- Trisomy 21 (usually - every cell of body)
- Characteristics
- mental retardation (mild to moderate)
- heart difficulties
- ear infections
- Do everything a regular kid can…ride a bike, walk, talk
- Slower to reach milestones
- Facial features
- There is no cure
Calculating risk for Down Syndrome (explain how they determine num.)Edit
- Look at maternal age + AFP MoM + hCG MoM + uE3 MoM = Down Syndrome Risk
- Risk ³ 1/270 is considered screen positive
- This is equal to the midtrimester DSR for 35 year-old women
- AMA woman's risk may be made less by the triple screen results, but it is still considered a test positive because of her age.
Recommendations for abnormal testsEdit
- Ultrasound for examination of physical abnormalities
- Down Syndrome
- Nuchal fold (2nd trimester)
- detects 34%
- Nuchal translucency (1st trimester)
- detects 77%
- Short femur/humerus (detects 80-90% when combined with one of the following two)
- Echogenic bowel
- Short ear
- Nuchal fold (2nd trimester)
- Down Syndrome
- Amniocentesis
- Explain procedure
- 1/200 risk for complications
- Can't detect all problems with the baby BUT will determine chromosome status
- Fetal karyotype
- Down Syndrome
- Triploidy
- Trisomies 13, 18
- Other chromosomal abnormalities
The Basics of PKDEdit
- Definition
- Multiple cysts in the kidney leading to kidney dysfunction
- Prevalance = 1/400 - 1/1000
- Characteristics
- 90% penetrant
- initial signs = high blood pressure, blood in urine (50%), pain in side, back or abdomen, UTI, kidney stones (20-30%)
- Final stage = renal failure (60%) after age 40
- Mitral valve prolaspse (26% compared to gen pop 2-3%)
- aneurysms (5-10%) - occurs in familial clusters
- liver cysts are possible
- Diagnosis/medical management
- renal ultrasounds
- only after age 30 is a negative ultrasound = 5% risk of disease
- computed tomography (CT) - to detect aneurysm
- MRI
- renal ultrasounds
- Prevention
- Diet control = avoid red meat, eat low protein diet, less salt, fresh fruits and veggies, drink lots of water, avoid caffeine
- Treatment
- For pain
- acetaminophren may help
- laparoscopic surgery to "unroof" cysts
- For renal failure
- dialysis
- renal transplant (75-80% of kidneys work for 5 years)
- For pain
- Inheritance (dominant more commonly - recessive is RARE)
- Description of autosomal dominant and why this is the type
- Chance of recurrence if the mother has it = 50% chance
- Chance of recurrence if the mother doesn't have it same as population risk= <1%???? approximately 10% of the PKD patient community became infected through spontaneous mutation, and not through inheritance.
- Genetics
- Two genes identified (a third suspected)
- PKD1 - 16p (90% of PKD) DX is earlier, progresses more rapidly, more likely to be hypertensive
- PKD2 - chromosome 4
- Testing is done through linkage
Her optionsEdit
- A amniocentesis for chromosome risk
- A renal ultrasound for herself (PKD surveillance)
- If it is negative and she is 30+, chance of having PKD is <5%
- Testing by linkage analysis for herself and family
- Costs approx. $2200 per family
- >95% accurate in families
- Prenatal determination (preferably after linkage has been established)
- CVS testing for linkage studies (9-15 weeks)
- Amniocentesis for linkage studies (15+ weeks)
Psychosocial issuesEdit
- How her brothers illness has affected her
- Scared about the possibility of having PKD?
- Worried about PKD for baby?
- Would a diagnosis of PKD influence a pregnancy decision?
- How would having a child with DS feel?
- Support and resources at home?
- Would the dx of DS influence pregnancy planning?
Resources for patientEdit
- [Polycystic kidney disease access center http://www.nhpress.com/pkd/]
- [www.adam.com http://www.adam.com]
NotesEdit
The information in this outline has not been updated since 2003.
Material obtained under GFDL Licence from http://en.wikibooks.org/wiki/Handbook_of_Genetic_Counseling
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