Spontaneous abortion. How long after will one test positive?

[DwayneEMTP]

I pulled a 28 year old woman into the clinic a few weeks back when I noticed her walking down a path with a significant limp and apparent RLQ guarding.

After an assessment I decided on appendicitis and/or ectopic pregnancy at the top of my differential. I know, not exactly a stretch.

Patient had no significant pain when pulling the effected knee to her chest, and when supine banging on her heel created no painful response either, afebrile, so, right, wrong or indifferent I was leaning towards an ectopic pregnancy. Pulse rate and B/P were elevated but I was comfortable that this was secondary to pain and not a bleed.

I asked for a pregnancy test from the nursing staff while I started organizing a medivac.

Final diagnosis was infection secondary to spontaneous abortion of an ectopic pregnancy with retained POC (products of conception).

The reason I mention all of this is that I dropped that off of my list because when I asked for the preg test results I was told, "It was negative. That's not it." I said, "Did you repeat the test to verify?" She said, "Yeah, it's not pregnancy."

So I changed my opinion to acute appendicitis though was still kind of nagged by the possibility of the pregnancy.

And that got me to wondering... How long after the abortion would she likely have still shown positive on a pregnancy test? I really, really wanted to call bullshit on her being given the tests, but I'm not sure if that would have been fair or not. Plus, it would likely have made no difference in their behavior for the next patient.

Does anyone have any idea? I've done the Google thing, and have found a variety of answers but none from a truly reputable source...

[chbare]

Dwayne, urine pregnancy tests can be positive for several weeks following a spontaneous abortion. Unfortunately, a urine pregnancy test is rather useless at quantifying hCG levels. If you have the resources, running serial serum hCG levels over several days and noting a downward trend can be quite helpful.

It's generally a good idea to st least entertain an OB/Gyn issue regardless of urine pregnancy results.

[paramedicmike]

What CHBARE said. A urine pregnancy test will be positive for up to several weeks post abortion. A quant HCG, especially a serial quant, is going to provide more information for you... if you have access to it (and I don't know if you do or not).

If you don't have access to it it might be worth while to argue for it. Serial quant HCGs can confirm pregnancy, help confirm ectopics (especially when presented with a case similar to yours) and/or help confirm that the abortion, spontaneous or otherwise, is complete.

The down side is I don't know how much it costs or how you guys run your labs over there.

[DwayneEMTP]

When we have them we just have simple urine tests.

My main questions is, is there a way for her to have aborted 5 days past yet show negative, confirmed, on a urine test?

[chbare]

Most urine pregnancy tests that are reasonably sensitive will likely be negative at the two week mark. A positive urine pregnancy test more than a full month following abortion would lead you to suspect incomplete abortion. However, your test was negative. This could mean a couple of things:

1) Interesting physiology with the patient.

2) Something may have been wrong with your tests or lot of tests.

Can you find somebody who is known to be pregnant and has a verified + test? You should be able to take a random sample of your pregnancy test kits and compare their results. I would rule that out first.

[akflightmedic]

based on my very limited knowledge....

False negatives are possible

False positives are impossible

Tests taken later in the day could read as a false negative as the concentration of HcG is not as concentrated as much as it is first pee of the morning (another reason they recommend testings to be done earlier in day as opposed to later)

[chbare]

False positives are possible and can have many causes.

[akflightmedic]

False positives are possible and can have many causes.

Please feel free to educate me as every piece of literature with the kits and the limited reading I have done on this says false positives are not possible as there has to be HcG for it to register. The only way to have HcG is if they are preggers....

Grasshopper is ready to receive....

[chbare]

Certain types of cancers and immune disorders can cause false positive results along with women who receive hCG injections as part of infertility treatment. I am sure there are other causes and operator error such as interpreting the test well after the recommended read time must also be condsidered.

[akflightmedic]

So these cases of false positives are more of a statistical outlier as opposed to a common occurrence...in the absence of cancer, autoimmune disease( which ones?) and someone receiving treatment in order to conceive then it is darn near impossible to have a false positive?