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OBGYN > OBGYN Labs & Diagnostics > Flashcards

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
Q

Describe the indications for liver enzyme testing in pregnancy

A
  • fatty liver of pregnancy: mild liver enzyme elevation (abnormal coag tests, rarely results in acute liver failure)
  • HELLP syndrome: elevated liver enzymes
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26
Q

Describe the labs for preterm labor testing

A

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)

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27
Q

Why would we check bile salts in late pregnancy

A

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

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28
Q

Describe the tests for rupture of membranes

A

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
Q

Describe which common labs are affected by pregnancy

A
  • 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
Q

List some labs that test for infertility

A
31
Q

Describe estrogen levels during menstruation, pregnancy, menopause

A
  • vary widely during menstrual cycle
  • increase steadily throughout pregnancy
  • higher in premenopausal women than postmenopausal
32
Q

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

A
  • checking for ovarian failure (fertility/menstrual problems)
  • monitoring hormone replacement therapy, breast cancer treatment meds
33
Q

Describe the levels of progesterone during menstrual cycle & pregnancy

A
  • low in first half of menstrual cycle and high during luteal phase
  • progesterone important in maintaining early pregnancy
34
Q

Describe the indications for checking a progesterone level

A
  • amenorrhea
  • fertility problems/treatments
  • history of miscarriages
35
Q

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

A

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
Q

Describe indications for androgen testing

A
  • 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
Q

Which meds can impact testosterone levels

A
  • OCPs, estrogens, anticonvulsants can INCREASE T
  • spironolactone can DECREASE T
38
Q

Describe the indications for testing TSH

A
  • sxs of thyroid disorder
  • screening pregnant pts at high risk of thyroid dysfunction
  • part of amenorrhea workup
39
Q

Describe testing & indications for prolactin levels

A
  • 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
Q

What meds can elevate prolactin levles

A

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

41
Q

Describe some factors that interfere with a pap smear

A
  • blood, mucus, inflammatory cells (more of an issue with slide-based vs liquid based testing)
  • lubricant (messes with both types)
42
Q

Describe the components of a pap smear

A
  • cytology test
  • screening for cervical cancer (21+)
  • sample ectocervix AND endocervix
  • can reflex to HPV testing (for high risk strains, NAAT)
43
Q

Describe the testing for hereditary breast and ovarian cancer syndrome

A
  • 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
Q

Describe the indications for BRCA1/2 testing

A
  • family history suspicious for hereditary breast and ovarian cancer syndrome
  • family history of one or both mutations
  • consult genetic counselor
45
Q

Describe testing of CA-125

A
  • 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
Q

How do you test for vaginitis

A
  • wet prep (quick, accuracy concerns)
  • molecular tests (long, accurate)

Test for yeast, bacterial, trich

47
Q

Describe the components of a wet prep

A

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
Q

What are these

A

Clue cells - BV

49
Q

What are these

A

pseudohyphae - yeast infection

50
Q

what are these

A

trichomonads - trichomoniasis

51
Q

What do vaginitis molecular tests assess for

A

yeast, bacterial, trich

52
Q

how do we test for GC/CT

A

Urine, vagina, endocervix, rectum, pharynx, NAAT

53
Q

How do we test for syphilis

A
  • non-treponemal
  • treponemal
  • blood tests
54
Q

how do we test for HSV

A

swab vesicular lesion or serologic testing

55
Q

When is a breast ultrasound indicated

A
  • eval of palpable mass
  • eval of abnormalities on mammogram
  • ideal imaging for dense breast tissue
  • US-guided breast biopsy
  • no radiation exposure
56
Q

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

A
  • 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
Q

Describe the gyn indications for a pelvic ultrasound (TVUS)

A
  • vaginal bleeding
  • pelvic pain
  • ovarian mass or enlarged uterus
  • infertility
  • IUD localization
58
Q

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

A
  • 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
Q

Describe some indications for a pelvic MRI

A
  • gyn malignancies
  • endometriosis
60
Q
A

Serum: detectable 8-11 days post conception (urine detectable ~2 weeks)

61
Q
A

first trimester screen

62
Q
A

neural tube defects

63
Q
A
  • abnormal FTS and/or quad screen
  • maternal age 35+
  • fetal US suggesting aneuploidy
  • previous aneuploid pregnancy
64
Q
A

infection, miscarriage, Rh sensitization

65
Q
A

around 36 weeks (vagina & rectum, treat with abx during labor if positive)

66
Q
A

False - high NEGATIVE predictive value

67
Q
A

A. high/basic pH

68
Q
A

false

69
Q
A

Around 20 weeks

OBGYN (22 decks)

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