OBGYN Labs & Diagnostics Flashcards by Elizabeth Sager

Describe the difference between urine hCG and serum hCG

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Which hCG test measures beta human chorionic gonadotropin

serum

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Describe the levels of hCG over the first 8 weeks of pregnancy

hCG doubles every 1.5-2 days for the firs 8 weeks

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Describe instances of a false negative on a urine pregnancy test

early pregnancy
very high hCG (hook effect)

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Describe instances of a false positive on a urine pregnancy test

heterophile antibodies (mono)
menopause (hCG secretion by pituitary)

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Describe the indications for a serum (quant) hCG

amenorrhea
early pregnancy
bleeding/abd pain in early pregnancy (ectopic pregnancies will not show hCG doubling as it should, spontaneous abortions will show a decreasing or improperly rising hCG)
monitoring after ectopic, miscarriage, gestational trophoblastic disease
hCG secreting tumors

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Describe hCG levels in an ectopic pregnancy

Do not double as it should (1.5-2 days for 8 weeks)

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Describe the components of a first trimester screen

(Trisomy 21, 18, 13)
at 10-14 weeks

Blood
- hCG
- pregnancy associated plasma protein A: protein from placenta

Ultrasound measurement of nuchal translucency for aneuploidy

THEN do a serum Alpha fetoprotein (neural tube defects) at 15-22 weeks

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Describe the components of a quad screen

(Trisomy 21, 18, 13, neural tube defects)
15-22 weeks

Blood tests only
- hCG
- estriol: predominant
- inhibin A: secreted by ovaries & placenta
- serum AFP: neural tube defects

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Describe the differences in quad screening between Trisomy 21 and Trisomy 18

Trisomy 21
- hCG elevated
- estriol decreased
- inhibin increased
- AFP decreased

Trisomy 18
- all decreased

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What can you determine from first trimester screening & quad screening

gestational age
maternal weight
number of fetuses
DM

Potential causes of abnormal results: incorrect dating, presence of twins, fetal demise

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Describe the indications for fetal anomaly screening

all pregnant patients (FTS or quad screen)
high risk patients: sequential screen (FTS AND quad screen)
if abnormal: cell free fetal DNA, chorionic villus sampling, amniocentesis

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Describe cell-free fetal DNA testing

maternal blood sample (10+ weeks gestation) DNA fragments amplified & sequenced
Trisomies will have a higher % of DNA fragments from the extra chromosome
very low false positive rate
Tests for trisomies & Turner syndrome (monosomy X)

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Describe the indications for fetal DNA based screening

pregnant patients at risk of fetal aneuploidy (AMA, abnormal fetal US, previous aneuploidy, abnormal screen)
offer neural tube ultrasound and/or AFP for neural tube defects

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Describe chorionic villus sampling

sample of chorionic villi removed from placenta via transcervical/transabdominal collection
11-14 weeks gestation
slight risk of miscarriage, Rh sensitization, infection
offer neural tube ultrasound and/or AFP for neural tube defects
indicated after positive screen & diagnoses trisomies or other genetic conditions (CF)

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Describe amniocentesis fetal anomaly testing

sample of amniotic fluid transabdominally
15-20 weeks
indications: genetic testing, fetal lung maturity, fetal infection/hemolytic disease, paternity testing
Risks: miscarriage, Rh sensitization, infection, amniotic fluid leak, needle injury

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Describe optional carrier screening

screens for 175+ genetic conditions
best done prior to conception, can be done during pregnancy
can test one or both partners

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Describe the routine tests in pregnancy at first prenatal visit (10-12 weeks)

Blood type & antibody screen (assess risk of hemolytic disease of the newborn)
CBC
RPR or treponemal syphilis test
Hep B surface antigen
HIV antibody (false positives)
Rubella antibody (vaccine after delivery if non-immune or equivocal)
GC/CT testing (treat if +)
urine culture (treat if asymptomatic bacteriuria)

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Describe the routine tests in pregnancy at 24-28 weeks

1 hr oral glucose tolerance test with reflex to 3 hour fasting if abnormal (for gestational DM)
Hgb and/or CBC (for anemia)

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Describe the routine tests in pregnancy done at around 36 weeks

group B strep culture (swab vagina AND rectum: give abx during labor if positive)

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Describe what a urine dip at a prenatal visit can tell us

Check for proteinuria & glucosuria
- protein: concern for preeclampsia (along with elevated BP)
- glucose: concern for gestational DM

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Describe testing done in recurrent pregnancy loss

karyotype (parental & fetal tissue if possible)
LH, FSH, TSH, PRL, cortisol (endo abnormalities)
thrombophilia panel: protein C & S, antithrombin, Factor V Leiden, prothrombin gene mutation, lupus antigoaculant, anticardiolipin Abs
ANtithyroid Abs
Test for DM (glucose, Hgb A1C)

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Describe when/why a CBC is checked in pregnancy

routine screening in early pregnancy
second trimester anemia check
symptoms of anemia
pregnancy complications
HELLP syndrome (hemolysis, low PLT, also get peripheral blood smear)

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Describe why a CBC is checked in gyn presentations

symptoms of anemia & menstrual abnormalities (menorrhagia)

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Describe the indications for liver enzyme testing in pregnancy

- fatty liver of pregnancy: mild liver enzyme elevation (abnormal coag tests, rarely results in acute liver failure) - HELLP syndrome: elevated liver enzymes

Describe the labs for preterm labor testing

Fetal fibronectin test - indicated in pts with sxs of preterm labor - 22-35 weeks - vaginal swab - HIGH NEGATIVE PREDICTIVE VALUE (protein produced at boundary between amniotic sac & uterus)

Why would we check bile salts in late pregnancy

testing for cholestasis of pregnancy (itching!) - blood test

Describe the tests for rupture of membranes

**Fern test** (amniotic fluid crystallizes in tree like pattern on slide) - sample vaginal fluid, let it dry, look for ferning under microscope - check pH of fluid (Nitrazine test)(amniotic fluid has high pH = BASIC) Amnisure (@ hospital) - sterile vaginal swab detects amniotic fluid protein (fast)

Describe which common labs are affected by pregnancy

- cholesterol/trigs: increased - hematocrit: decreased - Total T3/T4: increased (different reference ranges in each trimester of pregnancy for TSH) - alk phos: increased (placenta activity) - coag factors: increased (increased thrombotic risk)

List some labs that test for infertility

Describe estrogen levels during menstruation, pregnancy, menopause

- vary widely during menstrual cycle - increase steadily throughout pregnancy - higher in premenopausal women than postmenopausal

What are the indications for checking a serum/plasma estrogen (Estradiol/E2)

- checking for ovarian failure (fertility/menstrual problems) - monitoring hormone replacement therapy, breast cancer treatment meds

Describe the levels of progesterone during menstrual cycle & pregnancy

- low in first half of menstrual cycle and high during luteal phase - progesterone important in maintaining early pregnancy

Describe the indications for checking a progesterone level

- amenorrhea - fertility problems/treatments - history of miscarriages

Describe the indications for checking FSH/LH levels and how to interpret results

Indications - evaluation of reproductive dysfunction (high in ovarian failure) - part of amenorrhea workup - assessment of menopause (high) - may be low in corticosteroid use Interpretation (need to know) - age - tanner stage - sex - time of menstrual cycle (FSH highest in first half, LH highest right around ovulation)

Describe indications for androgen testing

- amenorrhea workup in women/AFAB with signs of androgen excess - PCOS (elevated) - adrenal hyperplasia Reference ranges of total/free T & DHEA-S lower in females - insulin, steroids can decrease

Which meds can impact testosterone levels

- OCPs, estrogens, anticonvulsants can INCREASE T - spironolactone can DECREASE T

Describe the indications for testing TSH

- sxs of thyroid disorder - screening pregnant pts at high risk of thyroid dysfunction - part of amenorrhea workup

Describe testing & indications for prolactin levels

- best to check serum level 3-4 hours after waking (fast overnight, no stress, exercise, significant activity prior) Indications - amenorrhea/galactorrhea workup - fertility (anovulation) - postpartum lactation issues (low PRL)

What meds can elevate prolactin levles

estrogens, haloperidol, cimetidine, TCAs (levodopa/dopamine can inhibit)

Describe some factors that interfere with a pap smear

- blood, mucus, inflammatory cells (more of an issue with slide-based vs liquid based testing) - lubricant (messes with both types)

Describe the components of a pap smear

- cytology test - screening for cervical cancer (21+) - sample ectocervix AND endocervix - can reflex to HPV testing (for high risk strains, NAAT)

Describe the testing for hereditary breast and ovarian cancer syndrome

- whole blood test - autosomal dominant - mutations in BRCA1 & BRCA2 genes - 5-10% of BC cases attributed to these mutations, they pose a 60-80% lifetime risk of BC (compared to 12.5% of gen pop)

Describe the indications for BRCA1/2 testing

- family history suspicious for hereditary breast and ovarian cancer syndrome - family history of one or both mutations - consult genetic counselor

Describe testing of CA-125

- serum test tumor marker - elevated in many pts with ovarian cancer but not all - elevated in pancreatic, colon, breast, stomach, endometrial cancers - normal CA-125 does not rule out cancer - false positives in endometriosis, PID, uterine fibroids - most useful in postmenopausal women

How do you test for vaginitis

- wet prep (quick, accuracy concerns) - molecular tests (long, accurate) Test for yeast, bacterial, trich

Describe the components of a wet prep

sample of vaginal secretions assessed for... - color/consistency - pH (<4.5 yest, >4.5 BV, >5 trich) - saline & KOH (saline for clue cells & trich, KOH for whiff test & fungi)

What are these

Clue cells - BV

What are these

pseudohyphae - yeast infection

what are these

trichomonads - trichomoniasis

What do vaginitis molecular tests assess for

yeast, bacterial, trich

how do we test for GC/CT

Urine, vagina, endocervix, rectum, pharynx, NAAT

How do we test for syphilis

- non-treponemal - treponemal - blood tests

how do we test for HSV

swab vesicular lesion or serologic testing

When is a breast ultrasound indicated

- eval of palpable mass - eval of abnormalities on mammogram - ideal imaging for dense breast tissue - US-guided breast biopsy - no radiation exposure

Describe the indications of a breast MRI (requires IV contrast)

- breast cancer screening in very high risk patient - checking for cancer in contralateral breast in pts newly diagnosed - breast cancer screening in pts with breast augmentation where mammo is difficult - breast cancer treatment

Describe the gyn indications for a pelvic ultrasound (TVUS)

- vaginal bleeding - pelvic pain - ovarian mass or enlarged uterus - infertility - IUD localization

Describe the OB indications for a pelvic ultrasound (TVUS or transabdominal)

- pelvic pain and/or bleeding (ectopic pregnancy, abortion) - pregnancy dating - nuchal translucency scan - fetal anomal scan - high risk pregnancies (biophysical profile, growth scans, cervical measurements, placental conditions)

Describe some indications for a pelvic MRI

- gyn malignancies - endometriosis