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khagihara, OB/GYN (Doctor)
Category: OB GYN
Satisfied Customers: 6414
Experience:  Trained in OB & GYN for many years.
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My wife and I are at the end of her first trimester today,.

Customer Question

Hi.. My wife and I are at the end of her first trimester today,. We have been to the doctor twice, last time was about a 1 and 1/2 weeks ago.. We heard the baby's heartbeat and everything was fine.. We took a pregnancy test today just to make sure everything is still fine and the pregnancytest had a very faint line when n the past it showed up dark. Can you please tell me if we should be concerned?
Submitted: 5 months ago.
Category: OB GYN
Expert:  TheGermDoctor replied 5 months ago.
are you still looking for a phone call?
Expert:  khagihara replied 5 months ago.
At serum levels of hCG above 500,000 mIU/mL, a "hook effect" can occur, resulting in an artifactually low value for hCG. I think the similar thing occurs in the urine sample. This is because the sensitivity of most hCG tests is set to the pregnancy hCG range (ie, 27,300 to 233,000 mIU/mL at 8 to 11 weeks of gestation). Therefore, when an extremely high hCG concentration is present, both the capture and tracer antibodies used in immunoradiometric assays become saturated, preventing the binding of the two to create a sandwich. Since the non-sandwiched tracer antibodies are washed away with the excess material, the test result will be negative. You should try to perform another urine hCG test at 1:1000 dilution. If it still causes faint line, she should go to her doctor to have ultrasound and measure the hCG levels at several dilutions.

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