Pregnancy, prenatal and neonatal testing Flashcards
What are the clinical indications for measuring hCG?
- Pregnancy
- Malignancy (gestational trophoblastic disease)
- Prenatal screening for fetal aneuoploidies
- Exogenous hCG (doping, hCG diet, Munchausen)
Describe the hCG molecule
145 AA beta subunit and 92 AA alpha subunit
The alpha unit of hCG is identical to what hormone?
LH, FSH and TSH
How many bioactive forms of hCG are there?
5
What are the 5 forms of hCG?
hCG sulfated hCG hyperglycosyclated hCG hCGB hyper]glycosylated hCGB
hCG (endocrine)
PREGNANCY
syncytiotrophoblast
LH/hCG receptor
sulfated hCG (endocrine)
PITUITARY
gonadotrope
LH/hCG receptor
Hyperglycosylated hCG (autocrine)
Pregnancy, GTD, testicular germ cell tumors
cytotrophoblast
TGFb antagonism
What two types of hCG are associated with advanced malignancies?
hCGB
hyperglycosylated hCGB
Both have TGFbeta antagonism
GTD
germ cell
advanced non torphoblastic
Free alpha subunit is quite elevated in both serum and urine of pregnant women. What issue prohibits its use as a good biomarker of pregnancy?
Antibodies that detect free alpha subunit would detect the alpha subunits of other hormones like LH, FSH and TSH
therefore it is NOT specific for pregnancy
What is an hCG assay best for diagnosing?
pregnancy?
What is the best platform for detecting cancer related hCG?
Siemens Immulite
What does a total hCG assay measure?
intact and free beta subunits
What is the only instrumentation recommended for use of both pregnancy and tumor marker?
Siemens immulite
What is the difference between qualitative vs quantitative hCG tests?
Qualitative:
- positive vs negative answer
- urine or serum
- positive if between 10-50
- measure intact hCG only
Quantitative
- numerical amount
- detection limit down to 2 IU
- more sensitive but WIDE variation in what forms are detected
What test should be done to diagnose early pregnancy if a patient’s period is less than a week late?
serum hCG because early pregnancies may have a positive serum test and negative urine test
(qualitative detects down to 10, quantitative down to 2)
Why are UPTs less sensitive?
they only detect hCG down to 20-50 IU/L
When does a gestational sac or intrauterine fluid appear?
4.5-5 weeks
When does the yolk sac appear?
5-6 weeks
What is an expected level of hCG if a patient’s period was 4 weeks ago?
72
3 weeks 12 4 weeks 72 5 weeks 521 6 weeks 1800 7 weeks 16,000 8 weeks 47, 000 9 weeks 64, 000 10 weeks 102, 000 11 weeks, 95,000
What is the expected rise in hCG after 2 days?
hCG should double (or atleast increase by half) every 30-53 hours during the first 30 days after implantation
What is the ddx for persistently low levels of hCG?
- Spontaneous abortion/resolving ectopic
- biochemical pregnancy
- GTC
- pituitary hCG (can be as high as 20-40)
- Active GTD (usually high)
- other tumors (bladder, uterine, lung, liver, pancreas)
- familial hCG syndrome
- false positive hCG
What is quiescent GTD?
– Typically occurs after completemole,butcanoccurafter choriocarcinoma, invasive moles and partial moles
– SofewcytotrophoblaststhathCGlevelsarelow(<212IU/L)
A urine pregnancy test is administered in the clinic and found to be negative. What is a possible cause for the discrepancy between serum and urine results?
Differing sensitivity of urine and serum assays:
– If the urine test “cut‐off” is 50 IU/L then urine test could be negative and hCG falling due to biochemical pregnancy or spontaneous abortion
• False positive or “phantom hCG” – Heterophile antibodies:
• Humanscangeneratehumananti‐humanantibodiesthatcross‐react with and bind animal antibodies
• AnimalantibodiesareusedinhCGtesting
• ThereforetheseantibodiescanrarelyinterferewithhCGassayscausing
a false positive
• Common in patients with IgA deficiency one study demonstrated false positive pregnancy tests in 30% of IgA deficient patients
– The key is that urine hCG is negative because the interfering antibodies are too large to be filtered into the urine
What is the ddx for a serum hCG of 301,120?
- Multiple gestation pregnancy
– Singleton pregnancies typically peak at 100,000 IU/L
– Highest reported in literature for singleton pregnancy is ~265,000 IU/L - Gestational trophoblastic disease
– 40% of complete moles have hCG > 100,000 IU/L
When should a physician initiate an infertility evaluation?
- Typically after 1 year of unprotected sex for woman < 35 years of age
- After 6 months for women 35 years and older
- Evaluation can be initiated earlier if the patient has known risk factors for infertility such as endometriosis or a history of pelvic inflammatory disease
- Recommended that both partners should begin evaluation for infertility simultaneously
What is the initial test that should be done in the evaluation for male infertility?
SEMEN ANALYSIS
- Men are asked to abstain from sex for 2‐5 days prior to giving a sample
- Ideallythespecimenshouldbeobtainedonsite in the laboratory
- Samplecanbeobtainedviamasturbationorless ideally using a special semen collection condom
- Ifcollectedathomethesampleshouldbe brought to the lab for examination within an hour and kept at body/room temp
What parameters are looked at for semen analysis?
Ejaculate volume pH sperm concentration total sperm number percentage moltility forward progression normal morphology sperm agglutination viscosity
What are the main causes of female infertility?
• Ovulatory dysfunction (25 %) – Includes PCOS, obesity, weight gain/loss, strenuous exercise, thyroid dysfunction • Endometriosis (15 %) • Pelvic adhesions (12 %) • Tubal blockage (11 %) • Other tubal abnormalities (11 %) • Hyperprolactinemia (7 %)
How can ovulatory function be evaluated?

• Menstrual history
– Women with abnormal uterine bleeding, oligo‐ or amenorrhea can generally be diagnosed with ovulatory dysfunction without further testing
• Serum progesterone
– Progesterone is produced by the corpus luteum after
ovulation
– Therefore it’s a reliable and objective measure of ovulatory function
– Should be measured approximately 1 week prior to expected menses (approximately when it peaks)
– Progesterone > 3 ng/mL is presumptive evidence of recent ovulation
• LH surge:
– Ovulation occurs ~36 – 40 hours after the LH surge
– Patients can use OTC urinary LH ovulation predictor kits – Confirm in serum if no surge detected
• Additional tests to identify cause of ovulatory dysfunction:
– TSH and prolactin to identify thyroid disorders or hyperprolactinemia
– FSH and estradiol
• High FSH, low estradiol in primary ovarian failure
• Low FSH, low estradiol in hypothalamic amenorrhea
What is ovarian reserve, why and how is it measured?
- Ovarian reserve is reproductive potential as a function of quality and quantity of oocytes
- Women with decreased ovarian reserve will have diminished response to ovarian stimulation
- Measure ovarian reserve with a cycle day 3 FSH and E2
• Anti‐mullerian hormone (AMH):
– Produced by granulosa cells of early follicles
– Can be measured any day of the cycle
– AMH < 1 ng/mL associated with poor response to ovarian stimulation, poor embryo quality, and poor pregnancy outcomes in IVF
• Antral follicle count (AFC):
– Transvaginal ultrasonography in early follicular phase
• Clomiphene citrate challenge test
– Involves measurement of FSH before and after treatment
with clomiphene citrate
– Use has declined since AMH and AFC are simpler and highly predictive of ovarian reserve
What levels of FSH and E2 are associated with poor response to stimlulation and lower pregnancy reates?
- FSH > 10 – 20 IU/L associated with failure to conceive and poor response to ovarian stimulation
FSH high because the reduced quantity/quality of oocytes leads to insufficient production of ovarian hormones, and thus insufficient inhibition of pituitary secretion of FSH
- If FSH is normal but E2 > 60 – 80 IU/L, also associated with poor response to stimulation and lower pregnancy rates
- Elevated E2 due to advanced premature follicle recruitment in women with poor ovarian reserve (typically seen with aging)
- High E2 suppresses FSH and thus it is in the normal range
What is the differential diagnosis for hypertension in pregnancy?
Preeclampsia‐eclampsia
• Chronic hypertension
• Combination of above
• Gestational hypertension • Other
What are the diagnostic criteria for preeclampsia?
ONE:
BP greater than or equal to 140 or greater than or equal to 90 on two occasions at least 4 hours apart after 20 weeks in a women with previously normal blood pressure
OR
BP greater than or equal to 160 ore greater than or equal to 110
PLUS
TWO: - greater than or equal to 300 mg per 24 hr urine collection OR - protein/cr ratio > .3 - dipstick reading 1 +
What is the definition of chronic hypertension vs. gestational hypertension?
- Chronic hypertension: hypertension that predates pregnancy
* Gestational hypertension: blood pressure elevation after 20 weeks gestation in the absence of proteinuria
What is the diagnosis in a patient with BP 180/106 and 3+ protein on ur dipstick? What tests should be ordered?
Preeclampsia based on 3+ protein in urine and blood pressure at > 20 weeks gestation exceeding 160 mm Hg systolic
Laboratory testing should include: – Platelet count – Serum creatinine – Serum AST or ALT – Additionally can perform blood smear, LDH and bilirubin
What is the diagnostic Criteria for HELLP syndrome?
– Microangiopathic hemolytic anemia with schistocytes on blood smear
• Elevated indirect bilirubin and low serum haptoglobin
– Platelets ≤ 100x109/L
– Total bilirubin ≥ 1.2 mg/dL
– Serum AST ≥ 70 U/L
Once HELLP has been diagnosed, what should be done next with this patient?
• Delivery is curative and offers the only effective treatment
• Delivery!
• Prompt delivery is indicated after maternal stabilization for
any of the following:
– Pregnancies ≥ 34 weeks of gestation (our patients is 35 2/7 weeks)
– Nonreassuring fetal status tests
– Presence of severe maternal disease i.e. multiorgan failure, DIC, liver infarct/hemorrhage, pulmonary edema, renal failure, abruptio placenta
• For patients ≤ 34 weeks, administer corticosteroids before delivering
– Do not recommend delaying delivery by more than 48 hours
Can preeclampsia be diagnosed in a patient lacking proteinuria?
Yes, if they have any of the signs/symptoms that define severe preeclampsia:
- thrombotcytopenia
- renal insufficiency
0 impaired liver fxn - pulmonary edema
- cerebral or visual sxs
In a patient with preeclampsia without severe features, what laboratory testing is recommended for routine monitoring?
Weekly assessment of platelet count and liver enzymes
The result of a new born screen show:
Phenylalanine
554 nmol/L (abnormal >130)
PHE/TYR ratio
15 (abnormal >2.5)
What are these findings suggestive of?
These findings are suggestive of a deficiency of the enzyme phenylalanine hydroxylase that causes hyperphenylalaninemia or phenylketonuria (PKU). More rarely these findings can reflect an impairment of tetrahydrobiopterin synthesis or recycling. Profound and irreversible mental retardation can occur if treatment for phenylketonuria (PKU) is not initiated shortly after birth.
When and how should newborn screening be performed?
• National standards require collection by heel stick
– Alternative methods available for NICU babies or babies with injured feet
• Heel stick sample must be obtained between 24 – 48 hours of age
– All normal values and reference ranges are validated for infants in this age window
– Early or late specimens may lead to false positives or negatives
– Specimens may be drawn early if the patient will be transfused
• Minnesota also mandates hearing screening and critical congenital heart disease (CCHD) screening
– Hearing screen should be at least 12 hours after birth
– CCHD screen involves pulse oximetry between 24 hours of age and discharge
Which disorders are part of the newborn screen?
a TON
What are the criteria for inclusion of a disorder in the newborn screening panel?
significant morbidity/mortality available/effective treatment time exists before onset of sxs so that intervention can be effective cost beneficial incidence in population to be screened
Once a primary care physician is notified of a positive newborn screen, what should be done next?
In Minnesota they tell you what to do on the report: Contact the genetics/metabolic specialist at the University of Minnesota Children’s Hospital, Children’s Hospitals and Clinics of Minnesota, or Mayo Clinic immediately.
Initiate confirmatory testing
What type of confirmatory testing does a patient with PKU need?
plasma amino acid profile
What immediate intervention should be taken for this child with PKU now that the diagnosis is confirmed?
• Place child on low phenylalanine diet
– Phenylalanine‐free formula called Periflex – Typically handled by a metabolic dietician
• Maintenance on a low‐phenylalanine diet will prevent mental retardation
An 18 month old presents to the ED with vomiting and lethargy. Mom states she tends to vomit “a lot.” Medical record shows a normal newborn screen. Is an inborn error of metabolism a possible diagnosis?
• Yes!
• Inborn errors of metabolism can present at ANY
stage of life, into adulthood
•Therearemanymetabolicdisorderswhere abnormal laboratory values only occur during acute decompensations
– Another illness can push these patients into acute metabolic decompensation
– Consumption or exposure to large load of compounds they cannot process can lead to toxic accumulation
What common laboratory tests are important for screening a patient in an acute metabolic crisis?
Ammonia CBC with diff glucose ABG and electrolytes BUN and Cr Uric acid
You order a plasma ammonia on the patient, and notice it sitting at the bedside in a rack an hour after it was drawn. Should you send it to the lab or re‐draw the specimen?
REDRAW!
Blood collected for ammonia measurement must be placed immediately on ice and sent ASAP to the laboratory
• Hemolysis, prolonged time at room temperature, and delayed processing will all falsely ELEVATE ammonia
• This can lead to incorrect diagnosis of hyperammonemia in patients
If an inborn error of metabolism is strongly suspected based on initial lab results or clinical presentation, what specialized tests are typically ordered to further screen for these disorders?
• Plasma amino acids • Urine organic acids • Plasma acylcarnitines • Serum lactate and pyruvate Answer 9 – Lactate:pyruvate ratio helpful in distinguishing mitochondrial disorders (generally high) from other IEM
