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OBGYN Labs & Diagnostics Flashcards

1
Q

Describe the difference between urine hCG and serum hCG

A
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2
Q

Which hCG test measures beta human chorionic gonadotropin

A

serum

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3
Q

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

A

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

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4
Q

Describe instances of a false negative on a urine pregnancy test

A
  • early pregnancy
  • very high hCG (hook effect)
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5
Q

Describe instances of a false positive on a urine pregnancy test

A
  • heterophile antibodies (mono)
  • menopause (hCG secretion by pituitary)
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6
Q

Describe the indications for a serum (quant) hCG

A
  • 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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7
Q

Describe hCG levels in an ectopic pregnancy

A

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

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8
Q

Describe the components of a first trimester screen

A

(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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9
Q

Describe the components of a quad screen

A

(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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10
Q

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

A

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

Trisomy 18
- all decreased

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11
Q

What can you determine from first trimester screening & quad screening

A
  • gestational age
  • maternal weight
  • number of fetuses
  • DM

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

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12
Q

Describe the indications for fetal anomaly screening

A
  • 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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13
Q

Describe cell-free fetal DNA testing

A
  • 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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14
Q

Describe the indications for fetal DNA based screening

A
  • 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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15
Q

Describe chorionic villus sampling

A
  • 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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16
Q

Describe amniocentesis fetal anomaly testing

A
  • 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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17
Q

Describe optional carrier screening

A
  • 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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18
Q

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

A
  • 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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19
Q

Describe the routine tests in pregnancy at 24-28 weeks

A
  • 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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20
Q

Describe the routine tests in pregnancy done at around 36 weeks

A
  • group B strep culture (swab vagina AND rectum: give abx during labor if positive)
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21
Q

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

A

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

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22
Q

Describe testing done in recurrent pregnancy loss

A
  • 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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23
Q

Describe when/why a CBC is checked in pregnancy

A
  • 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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24
Q

Describe why a CBC is checked in gyn presentations

A

symptoms of anemia & menstrual abnormalities (menorrhagia)

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25
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
26
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)
27
Why would we check bile salts in late pregnancy
testing for cholestasis of pregnancy (itching!) - blood test
28
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)
29
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)
30
List some labs that test for infertility
31
Describe estrogen levels during menstruation, pregnancy, menopause
- vary widely during menstrual cycle - increase steadily throughout pregnancy - higher in premenopausal women than postmenopausal
32
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
33
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
34
Describe the indications for checking a progesterone level
- amenorrhea - fertility problems/treatments - history of miscarriages
35
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)
36
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
37
Which meds can impact testosterone levels
- OCPs, estrogens, anticonvulsants can INCREASE T - spironolactone can DECREASE T
38
Describe the indications for testing TSH
- sxs of thyroid disorder - screening pregnant pts at high risk of thyroid dysfunction - part of amenorrhea workup
39
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)
40
What meds can elevate prolactin levles
estrogens, haloperidol, cimetidine, TCAs (levodopa/dopamine can inhibit)
41
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)
42
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)
43
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)
44
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
45
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
46
How do you test for vaginitis
- wet prep (quick, accuracy concerns) - molecular tests (long, accurate) Test for yeast, bacterial, trich
47
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)
48
What are these
Clue cells - BV
49
What are these
pseudohyphae - yeast infection
50
what are these
trichomonads - trichomoniasis
51
What do vaginitis molecular tests assess for
yeast, bacterial, trich
52
how do we test for GC/CT
Urine, vagina, endocervix, rectum, pharynx, NAAT
53
How do we test for syphilis
- non-treponemal - treponemal - blood tests
54
how do we test for HSV
swab vesicular lesion or serologic testing
55
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
56
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
57
Describe the gyn indications for a pelvic ultrasound (TVUS)
- vaginal bleeding - pelvic pain - ovarian mass or enlarged uterus - infertility - IUD localization
58
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)
59
Describe some indications for a pelvic MRI
- gyn malignancies - endometriosis
60
Serum: detectable 8-11 days post conception (urine detectable ~2 weeks)
61
first trimester screen
62
neural tube defects
63
- abnormal FTS and/or quad screen - maternal age 35+ - fetal US suggesting aneuploidy - previous aneuploid pregnancy
64
infection, miscarriage, Rh sensitization
65
around 36 weeks (vagina & rectum, treat with abx during labor if positive)
66
False - high NEGATIVE predictive value
67
A. high/basic pH
68
false
69
Around 20 weeks

OBGYN (22 decks)

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