Reproductive System (Test of Pregnancy and Fetal well-being) Flashcards
-hCG production starts a few days after ________, and before _________
-it enters maternal circulation immediately after ____________
-hCG concentration in maternal blood rises exponentially, doubling every__ days
-excellent marker for confirming pregnancy
-levels detectable by some pregnancy tests within __-__ days post-implantation and should be detectable by all tests within __ days
fertilization; implantation
implantation
2
3-4
7
-hCG levels rise sharply and peak about __-___ weeks after fertilization
-it then sharply decreases to a stable low level for the remainder of gestation
8-10
hCG Structure
-glycoprotein composed of 2 polypeptide subunits: alpha and beta joined non-covalently
-____ subunit identical pituitary hormones FSH, LH and TSH
-___ subunit unique to hCG
-commercial test kits are generally beta-specific
alpha
beta
Qualitative hCG Analysis
-_________ test using serum or urine is used to confirm pregnancy
-specimen collection
—–serum: _______ sensitivity than urine in earliest weeks of pregnancy
—–urine: _______ _______ specimen preferred; most concentrated; other/more dilute urine may test negative initially
Qualitative
greater
first morning
this Qualitative hCG test uses solid phase, double-antibody, enzyme immunoassay
-utilizes 2 antibodies that recognize different epitopes on hCG molecule:
—–one specific for alpha subunit
—–other specific for beta subunit
sandwich assay:
1st Ab is anti-____, mouse monoclonal
2nd Ab is anti-___, goat polygonal
-_____-______ system
—-reagents immobilized on membrane of reaction disc
-reaction disc contains “On Board Controls: 1 negative and 1 positive
sensitivity:
detects hCG as low as 25 mIU/mL
(as early as 3-4 days after implantation)
Test Pack +Plus hCG COMBO with OBC
anti-alpha
anti-beta
flow-through
Test Procedure
Specimens and reagents should be at room temperature
- remove disc from the pouch
- draw specimen to the line marked on the transfer pipette supplied
- dispense contents into the Sample Well
——-specimen migrates across the membrane
——-you will see a light pink colour move through the window - read results at exactly __ minutes
5
Basic Test Principle
-specimen (serum/urine possibly containing hCG) migrates across membrane & reacts with/mobilizes (makes it move) the first antibody: anti-alpha hCG antibody complex
-this first complex continues to migrate across membrane to react with/be captured by immobilized anti-beta hCG antibody (capture region), then continues to end of membrane
-if hCG is present in specimen it is detected by the enzyme-labelled-antibody which converts a colourless substrate to a coloured chromogen = positive test
How does it work?
How does it work?
How does it work?
How does it work?
How does it work?
How does it work?
Limitations
False ________
-urine specimen too dilute
-specimen collected too early in pregnancy
False ______
-some post-menopausal specimens (low hCG levels unrelated to pregnancy)
-conditions other than pregnancy (hCG-producing tumours e.g. choriocarcinoma)
-nonspecific hCG-like substances
-specimens that originally test as positive during first few days post-conception may later be negative due to natural termination of pregnancy
——occurs in 31% of all pregnancies (22% are unrecognized)
——-request a repeat test (using serum specimen)
-urine preservatives which lower specimen pH < 3 will interfere
Negative
Positive
Quantitative analysis of hCG
useful when qualitative testing inconsistent with clinical evidence
- diagnosis of ________ pregnancy
—–implantation outside uterus
—–hCG levels are lower for gestational age
—–collect serial specimens
——hCG levels fall rather than rise
———-normal pregnancy: levels double every 48 hrs between 4 and 7 weeks gestation——– - impending spontaneous abortion (miscarriage)
- multiple pregnancies (______ levels)
4.detection & follow-up of hCG-producing tumours
——tumour marker test
——-germ cell tumours (ovary, testes)
- Down Syndrome
ectopic
higher
