OBGYN Labs & Diagnostics Flashcards
Describe the difference between urine hCG and serum hCG
Which hCG test measures beta human chorionic gonadotropin
serum
Describe the levels of hCG over the first 8 weeks of pregnancy
hCG doubles every 1.5-2 days for the firs 8 weeks
Describe instances of a false negative on a urine pregnancy test
- early pregnancy
- very high hCG (hook effect)
Describe instances of a false positive on a urine pregnancy test
- heterophile antibodies (mono)
- menopause (hCG secretion by pituitary)
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
Describe hCG levels in an ectopic pregnancy
Do not double as it should (1.5-2 days for 8 weeks)
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
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
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
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
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
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)
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
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)
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
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
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)
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)
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)
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
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)
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)
Describe why a CBC is checked in gyn presentations
symptoms of anemia & menstrual abnormalities (menorrhagia)
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
Serum: detectable 8-11 days post conception (urine detectable ~2 weeks)
first trimester screen
neural tube defects
- abnormal FTS and/or quad screen
- maternal age 35+
- fetal US suggesting aneuploidy
- previous aneuploid pregnancy
infection, miscarriage, Rh sensitization
around 36 weeks (vagina & rectum, treat with abx during labor if positive)
False - high NEGATIVE predictive value
A. high/basic pH
false
Around 20 weeks
