What is the acuacy of blood pregnancy tests?  If one was not pregnant
and thought they were what could it be? What illness or disorder would
cause pregnancy symptoms, such as morning sickness, late period?

Hi! Thanks for the question.

I will answer your query in a point-by-point manner.

What is the accuracy of blood pregnancy tests?

“Doctors can accurately diagnose pregnancy with a blood test within a
few days after a missed period.”

“Blood pregnancy tests, offered only by physicians, are the most
expensive, but also the most accurate. They can establish pregnancy
before a period is missed, and can also estimate how far along the
pregnancy is. Blood tests are virtually 100 percent reliable. To
confirm your pregnancy, the doctor will follow up with a pelvic exam,
to see if the uterus has enlarged.”

“Diagnosing Pregnancy”
http://www.mtauburn.caregroup.org/htinfo/Women/diagpreg.asp 


In answering your question, I consulted with a medical professional on
the accuracy of blood tests in pregnancy. The figure isn’t 100% as
compared to the one above but it is pretty accurate. According to him,
if the result is positive it is 99% accurate. Meanwhile if it is
negative, the accuracy drops a little bit to 98%.


When talking about blood pregnancy tests, it is usually compared with
the accuracy of home pregnancy tests. Blood pregnancy tests seem more
accurate since in a clinical laboratory, the test is more controlled
and thus less error occurs during the procedure.

“Most pregnancy tests claim 99 percent accuracy. In general, if
instructions are followed carefully, tests are 95 percent sensitive
and specific. That means that 95 percent of the positive tests will
accurately confirm pregnancy and 95 percent of the negative tests will
be accurate in determining a negative pregnancy status. Five times out
of 100, the test will be inaccurate, even if done correctly. Accuracy
is dependent on ease of use, because the simpler the instructions, the
more likely the women are to perform the test correctly. Test kits
that show a clear obvious result are easier to interpret.”

“Lab pregnancy tests (qualitative tests) use the same technology as
home pregnancy tests and they are similar in accuracy. They can be
more reliable, however, because they are done under strict protocols
by professionals who do such testing frequently. Quantitative hCG
tests are the most reliable but they require two blood tests drawn 36
to 48 hours apart. HCG levels should double during this time.”

“Home pregnancy test primer”
http://www.parentsplace.com/print/0,,244736,00.html?arrivalSA=1&arrival_freqCap=2


2. If one was not pregnant and thought they were what could it be?
What illness or disorder would cause pregnancy symptoms, such as
morning sickness, late period?

The following conditions are alternative diagnosis for pregnancy that
may cause these symptoms.

1. Menopause
2. Eating Disorder
3. Ovarian Cancer
4. Ectopic Pregnancy
5. Breast Cancer
6. Prolactinoma

“Misdiagnosis of Pregnancy”
http://www.wrongdiagnosis.com/p/pregnancy/misdiag.htm


Search terms used:             
Pregnancy accuracy blood tests hcg alternative diagnosis misdiagnosis
    
I hope these links would help you in your research. Before rating this
answer, please ask for a clarification if you have a question or if
you would need further information.
            
Thanks for visiting us.            
            
Regards,            
Easterangel-ga            
Google Answers Researcher

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Clarification of Answer by easterangel-ga on 23 Sep 2003 01:02 PDT

Hi again!

My good friend pinkfreud-ga passed on this additional information for
another condition that is usually misdiagnosed as pregnancy.

Pseudocyesis
http://www.infoplease.com/ce6/sci/A0840377.html

Thanks again!

Easterangel-ga

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Request for Answer Clarification by bakegoodz-ga on 23 Sep 2003 10:52 PDT

Could a thyroid disorder trigger pregnancy conditions?

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Request for Answer Clarification by bakegoodz-ga on 23 Sep 2003 10:54 PDT

I mean "pregnancy symptoms"

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Clarification of Answer by easterangel-ga on 23 Sep 2003 17:16 PDT

It seems that the most possible misdiagnosis of pregnancy that will
have a chance of a thyroid disorder is Hypothyroidism. Here is an
overview of Hypothyroidism.

Hypothyroidism
http://dictionary.reference.com/search?q=hypothyroidism&r=67


The link of Hypothyroidism and pregnancy will be one of the
alternative diagnosis for pregnancy, which is Prolactinoma.

Misdiagnosis of Hypothyroidism 
http://www.wrongdiagnosis.com/h/hypothyroidism/misdiag.htm


"Prolactinoma: A prolactinoma is a benign tumor of the pituitary gland
that produces a hormone called prolactin. It is the most common type
of pituitary tumor"

"Prolactin stimulates the breast to produce milk during pregnancy."

"Introduction: Prolactinoma"
http://www.wrongdiagnosis.com/p/prolactinoma/intro.htm

This article also connects Hypothyroidism and pregnancy.

"'The signs and symptoms of hypothyroidism are nonspecific and can be
masked by pregnancy; blood tests are the best way to make such a
diagnosis. It now appears that maternal thyroid hormone deficiency can
be added to the list of correctable maternal conditions that can have
an important impact on the fetus.'"

"Pregnant Women Should Be Tested for Thyroid Disorder To Prevent
Mental Deficiencies in Unborn Children"
http://medicalreporter.health.org/tmr0999/pregnant_women_should_be_tested.html


If you want to take a look at a list of signs of symproms of
pregnancy, the following websites provide a good list.

WebMD Fertility Center
http://www.babymed.com/docs/english/21.asp

"Signs of Pregnancy"
http://www.childbirth.org/articles/pregnancy/signs.html

I hope the additional information enhances my original answer.

Best Regards,
Easterangel-ga

Good as expected, thank you.

I read in "What To Expect When You're Expecting" that some children
have been born 7 months after a doctor assured the mother they weren't
pregnant. I've read a lot of reports from women online about this as
well -- one woman took a test at home and it was negative and the next
week she took one at the doctor's which was negative as well. She took
yet ANOTHER one 3 days later and it was positive. It seems that since
pregnancy is so individualized it is very hard to tell even with all
those tests.