Pregnant but Negative Urine Preg?

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Specializes in Emergency Room.

Hi all! I'm an ER nurse, and had a pt last noc who swore up and down "there's no way I can be pregnant....my period is 4 days late, but I took a test (urine) this morning and it was negative" The doc wanted to do a serum beta, and lo and behold PREGNANT! Thought I would come to the source and see if any of you guys know how common this is. I've had a couple in the last 6 months (one was a urine preg we did 2 days previous, pt came back and we did a beta).

Anyone know what the percentage is of women who don't show positive on urine HCGs?

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Specializes in emergency.

usually takes 7-10 days for the urine testto show... could be explanation????

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Specializes in Critical Care.

With my third one, I took three HPT's. All turned out negative, including the one I took the morning of a doctor appointment using the same sample of FMU. When the doctor came to talk to me she said she had never seen the line show up so fast in all her career.

So, yeah, those urine tests can be wrong. Don't know about a percentage however.

tvccrn

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Specializes in Looking for a career in NICU.
Hi all! I'm an ER nurse, and had a pt last noc who swore up and down "there's no way I can be pregnant....my period is 4 days late, but I took a test (urine) this morning and it was negative" The doc wanted to do a serum beta, and lo and behold PREGNANT! Thought I would come to the source and see if any of you guys know how common this is. I've had a couple in the last 6 months (one was a urine preg we did 2 days previous, pt came back and we did a beta).

Anyone know what the percentage is of women who don't show positive on urine HCGs?

I wonder how far along she is....I read somewhere years ago (not sure if it is a myth or not) that a standard pregnancy test will only show up positive for so many months, and after that, it won't.

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Specializes in Critical Care, Cardiothoracics, VADs.

What does the package insert say? The manufacturer would have to give the failure rate on there.

Actually, I looked up the FDA website and it says the "99% accurate" that the packet claims is compared to other tests, not to actual pregnancy!

The accuracy depends on the level of HCG in the urine, and how well you do the test. Mishandling of the test kit can give inaccurate results.

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Specializes in FNP, Peds, Epilepsy, Mgt., Occ. Ed.
I wonder how far along she is....I read somewhere years ago (not sure if it is a myth or not) that a standard pregnancy test will only show up positive for so many months, and after that, it won't.

I've seen a urine pregnancy test in a lab show positive two weeks after delivery.

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Specializes in Cardiac.
usually takes 7-10 days for the urine testto show... could be explanation????

Not true. HCG will show up in the urine very soon after implantation (can be as early as the next day). Implantation takes 7-10 days after ovulation. Your period can take 12-18 days to come after ovulation. So, a period that's 4 days late has plenty of time to show HCG. But right after implantation it will show up in the urine very soon after. It can be detected around 5 days before a missed period.

However, HPTs are notorious for having false negatives, and women are notorius for not using them properly.

To the OP, do you remember the beta numbers?

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Specializes in Cardiac.
I've seen a urine pregnancy test in a lab show positive two weeks after delivery.

LOL, the HCG doesn't fall out with the baby! It is a chemical that stays around for a while. Women who miscarry (early-like only 5 weeks along) will still have hcg for a while after, and sometimes up to 2 weeks. Your body has to eliminate it!

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Specializes in Emergency Room.

Her quant was barely 100.

Very interesting replies...keep 'em coming!

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Specializes in Cardiac.
Her quant was barely 100.

Very interesting replies...keep 'em coming!

I'd give my right kidney for a hCG of a hundred!

Our baseline is less than 5 and HPTs read at the lowest at 25. Some brands like First Response and some ever worse brands read at 100 or more. If she was using a brand like that then she won't show up on it.

FYI the best and most accurate HPT is the equate at Walmart.....

POAS ~ HPT FAQ

(for people who are really interested about HPTs)

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Specializes in NICU.
I'd give my right kidney for a hCG of a hundred!

Our baseline is less than 5 and HPTs read at the lowest at 25. Some brands like First Response and some ever worse brands read at 100 or more. If she was using a brand like that then she won't show up on it.

FYI the best and most accurate HPT is the equate at Walmart.....

POAS ~ HPT FAQ

(for people who are really interested about HPTs)

Hep, a lot of the store-brand HPTs won't give you a positive unless your HCG is over 100. So if she was barely 100 by blood in the evening, I can see how she'd be under that in the morning. Plus some women don't put enough urine on the test strips or if they drink a ton of water the sample might be diluted...

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LOL, the HCG doesn't fall out with the baby! It is a chemical that stays around for a while. Women who miscarry (early-like only 5 weeks along) will still have hcg for a while after, and sometimes up to 2 weeks. Your body has to eliminate it!

?? Doesn't the fact that the HCG stays positive indicate a molar pregnancy or something like that? I thought that the increased HCG after a miscarriage indicates molar and then in turn that the increased HCG can lead to endometrial cancer? I may be confused....

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