Pregnancy Testing and Human Chorionic Gonadotropin (HCG) Lecture

Flashcards covering the biological markers, clinical timelines, obsolete bioassays, and modern immunoassay techniques for pregnancy testing.

Human Chorionic Gonadotropin (HCG)

A glycoprotein hormone secreted by the trophoblast of the developing embryo that acts as a marker for pregnancy and certain tumors.

Trophoblast

The outer coating of the blastocyst that eventually develops into the placenta and produces HCG.

Morula

The stage of cell division reached several days after fertilization, prior to becoming a blastocyst.

Blastocyst

The stage of development occurring approximately on the 5th day after fertilization; its outer coating is the trophoblast.

Hydatidiform mole

A gestational trophoblastic disease that occurs when an empty egg cell is fertilized, resulting in a tumor that produces HCG.

Alpha subunit of HCG

A dimeric protein subunit of HCG that is similar to Luteinizing Hormone (LH), Follicle-Stimulating Hormone (FSH), and Thyroid-Stimulating Hormone (TSH).

Beta subunit of HCG ($\beta\text{-hCG}$)

A unique subunit of HCG that helps maintain the corpus luteum and stimulate progesterone production during the first 6-8 weeks of conception.

Corpus luteum

The remaining space in the ovary after an oocyte is released; it is responsible for producing progesterone to thicken the uterine lining.

25 mIU/mL

The standard detectable amount (cut off point) of $\beta\text{-hCG}$ in urine or serum to confirm pregnancy.

HCG doubling time

The physiological rate where HCG concentration increases twice every 24 hours until reaching peak levels.

Non-viable pregnancy indicator

Occurs when HCG levels plateau before 8 weeks or fail to double in concentration every 24 hours, suggesting a possible miscarriage.

Fetal Down Syndrome marker

A condition indicated when HCG levels in the maternal serum are twice ($2\times$) higher than regular levels.

Ascheim-Zondek test

An obsolete bioassay using immature female mice; a positive result is the formation of hemorrhagic follicles and corpora lutea.

Friedman test

An obsolete bioassay using a mature virgin female rabbit; urine is injected into the marginal ear vein.

Hogben test

An obsolete bioassay using the female South African clawed frog ($\text{Xenopus laevis}$); a positive result is oogenesis and ovulation.

Galli-Mainini test

The only obsolete bioassay that utilizes a male animal (frog or toad) to detect $\beta\text{-hCG}$ via spermatogenesis.

Frank-Berman test / Kupperman test

Obsolete bioassays using female rats where a positive result is indicated by ovarian hyperemia.

Complement fixation (Positive result)

An immunoassay result characterized by NO LYSIS because HCG-antibody complexes fix the complement.

Hemagglutination-inhibition (Positive result)

An immunoassay result characterized by NO AGGLUTINATION because HCG in the specimen neutralizes the anti-hCG reagent.

Direct agglutination (Positive result)

An immunoassay result where the presence of HCG directly leads to visible agglutination of latex particles or RBCs coated with anti-HCG.

Lateral Flow Enzyme Immunoassay

The full name of the principle used in home-based pregnancy kits, involving anti-hCG impregnated on a membrane strip.

Specific Gravity ($S.G.$)

A measurement of urine concentration; for home pregnancy tests, it should be at least $1.015$.

Control line (2nd line)

The line on a pregnancy kit strip containing anti-anti HCG that must turn red to indicate the test is valid.

Chorioepithelioma

A tumor of the trophoblastic cells that can lead to a false positive HCG result.