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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?.
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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? Alpha Subunit • Glycoprotein • First measurable placental product • Supports the corpus luteum - Beta Subunit
How does the test work? Tracer Antibody Capture Antibody
Antibody Sandwhich Tracer Antibody Alpha Subunit Beta Subunit Capture Antibody
How early will it be positive? Depends…
Detection Level: Urine: Above 25 HCG Trends
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
Is Dilution really a problem? • Standard of 1.010 - 1.015 • QuickVue: “1.007” • Need more data to be 100% sure
“Doubling Time” 66% 53%
Summary • Ab Sandwhich • As early as 28 days post LMP • Remember false + and false - • Minimum 53% rise in 2 days