Handbook of Genetic Counseling/Abnormal Triple Screen and Family History of PKD

Abnormal Triple Screen and Family History of PKD

IntroductionEdit

  • 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?

Medical History (related to PKD)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

Serum markers resultsEdit

  • AFP >2.5 MoM indicates a normal AFTN
  • AFP <0.75 MoM indicates a Trisomy 21

  • hCG >2.5 MoM indicates a Trisomy 21
  • hCG <0.55 MoM indicates a Trisomy 18

  • E3 <0.8 MoM indicates a Trisomy 18 or 21

Patient's resultsEdit

  • AFP =1.oo , HcG=2.21 , UE3=0.99
  • 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
  • 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 (Polycystic Kidney Disease)
    • Multiple cysts in the kidney leading to kidney dysfunction
  • Prevalence = 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
  • 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)
  • 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

NotesEdit

The information in this outline has not been updated since 2003.

Last modified on 15 June 2013, at 03:09