Human Chorionic Gonadotropin

Photo of average

14 y.o. patient at

the Children’s

ED

6 Questions

How Early is it detectable?

Causes of false +ve urine HCG?

Causes of false -ve urine HCG?

U/S findings at different hCG levels?

Does dilution really matter?

Is doubling time accurate?

How long does it take to get back?

Urine: 3 minutes

Serum: 1 hour

Ascheim-Zondek test: 100 hours

What is HCG?

• Glycoprotein

• First measurable placental product

• Supports the corpus luteum

-

Alpha Subunit

Beta Subunit

How does the test work?

Tracer Antibody

Capture Antibody

Tracer Antibody

Capture Antibody

Alpha Subunit

Beta Subunit

Antibody Sandwhich

How early will it be positive?

Depends…

HCG Trends

Day HCG (mIU/ml)

1 0.65

2 2.21

3 5.2

4 11.83

5 25.22

6 51.87

7 87.88

Detection Level:

Urine: Above 25

Ddx (+) hCG

• Physiologic artifact

• Exogenous hCG

• Gestational Trophoblastic Disease

• HAAA

• Non-gestational malignancy

False Negative Ddx

• Early Pregnancy • Hook Effect• Expired test• Sensory deficit• Inadequate test time

What should I see and when should I see it

Is Dilution really a problem?

• Standard of 1.010 - 1.015

• QuickVue: “1.007”

• Need more data to be 100% sure

Is doubling-time accurate?

“Doubling Time”

66%53%

Summary

• Ab Sandwhich

• As early as 28 days post LMP

• Remember false + and false -

• Minimum 53% rise in 2 days