Home-Use Tests - Pregnancy
Basic Information
What does this test do?
This is a home-use test kit to measure human chorionic gonadotropin
(hCG) in your urine. You produce this hormone only when you are
pregnant.
What is hCG?
hCG is a hormone produced by your placenta when you are pregnant.
It appears shortly after the embryo attaches to the wall of the
uterus. If you are pregnant, this hormone increases very rapidly.
If you have a 28 day menstrual cycle, you can detect hCG in your
urine 12-15 days after ovulation.
What type of test is this?
This is a qualitative test -- you find out whether or not you
have elevated hCG levels indicating that you are pregnant.
Why should you do this test?
You should use this test to find out if you are pregnant.
How accurate is this test?
The accuracy of this test depends on how well you follow the
instructions and interpret the results. If you mishandle or misunderstand
the test kit, you may get poor results.
Most pregnancy tests have about the same ability to detect hCG,
but their ability to show whether or not you are pregnant depends
on how much hCG you are producing. If you test too early in your
cycle or too close to the time you became pregnant, your placenta
may not have had enough time to produce hCG. This would
mean that you are pregnant but you got a negative test
result.
Because many women have irregular periods, and women may miscalculate
when their period is due, 10 to 20 pregnant women out of every
100 will not detect their pregnancy on the first day of their
missed period.
How do you do this test?
For most home pregnancy tests, you either hold a test strip in
your urine stream or you collect your urine in a cup and dip your
test strip into the cup. If you are pregnant, most test strips
produce a colored line, but this will depend on the brand you
purchased. Read the instructions for the test you bought and follow
them carefully. Make sure you know how to get good results. The
test usually takes only about 5 minutes.
The different tests for sale vary in their abilities to detect
low levels of hCG. For the most reliable results, test 1-2 weeks
after you miss your period. There are some tests for sale that
are sensitive enough to show you are pregnant before you miss
your period.
You can improve your chances for an accurate result by using
your first morning urine for the test. If you are pregnant, it
will have more hCG in it than later urines. If you think you are
pregnant, but your first test was negative, you can take the test
again after several days. Since the amount of hCG increases rapidly
when you are pregnant, you may get a positive test on later days.
Some test kits come with more than one test in them to allow you
to repeat the test.
Is this test similar to the one my doctor uses?
The home pregnancy test and the test your doctor uses are similar
in their abilities to detect hCG, however your doctor is probably
more experienced in running the test. If you produce only a small
amount of hCG, your doctor may not be able to detect it any better
than you could. Your doctor may also use a blood test to see if
you are pregnant. Finally, your doctor may have more information
about you from your history, physical exam, and other tests that
may give a more reliable result.
Does a positive test mean you are pregnant?
Usually, but you must be sure to read and interpret the results
correctly.
Do negative test results mean that you are not pregnant?
No, there are several reasons why you could receive false negative
test results. If you tested too early in your cycle, your placenta
may not have had time to produce enough hCG for the test to detect.
Or, you may not have waited long enough before you took this test.
Where can you get more information about pregnancy and pregnancy
tests?
Safety Tips
Home Pregnancy Tests – How to Use a Popular
Test Wisely
(posted 4/2/04)
The first home pregnancy tests were marketed in the mid 1970’s.
These tests are one of the most popular products for home diagnostic
testing. It is estimated that about 33% of women have used these
tests. The tests are popular because they allow women rapid access
to highly sensitive and personal information. These tests can lead
to earlier diagnosis and can provide pregnant women an opportunity
to seek earlier health care intervention.
FDA is involved in the premarket review of these tests. Since the
1976 Medical Device Amendment, FDA assures that new pregnancy tests
perform as well as those tests on the market since 1976. Premarket
compares test performance between a new test and an established
test. In these kinds of pregnancy devices the new test is compared
to varying levels of the hormone human chorionic gonadotropin (hCG)
that is the marker for pregnancy.
Recent investigators point out that the FDA review of analytical
performance does not always mean a woman is pregnant. This discrepancy
is because different tests have different abilities to detect low
levels of hCG. Also hCG levels differ between pregnant women depending
on the timing of the onset of pregnancy with regard to a menstrual
period and depending on each woman’s unique biology.
The result is that pregnancy tests may be labeled up to 99% accurate
when compared to other hCG tests, not to pregnancy. This may be
true based on information submitted to the FDA. Therefore, labeling
of these tests should clearly indicate that there is a possibility
for both false positive tests and false negative tests, so patients
should contact their health care provider to discuss any result.
Patients may frequently recognize incorrect results with the passage
of time. False negatives may be detected by ongoing failure to have
a period or the development of other obvious signs of pregnancy.
False positives may be demonstrated by the unexpected onset of menses
(regular vaginal bleeding associated with “periods”.)
Repeat testing and/or other investigations such as ultrasound may
provide corrected results.
If a patient has a negative result, it is always wise to consider
this a tentative finding. Women should not use medications and should
consider avoiding potentially harmful behaviors, such as smoking
or drinking alcohol, until they have greater certainty that they
are not pregnant.
Since September of 2003, studies for pregnancy tests have been
posted on the Office of In Vitro Diagnostic Web Page (www.fda.gov/cdrh/oivd/)
under new 510(k)s – decision summaries. FDA is considering
what educational or regulatory tools might be available to help
clarify the status, use, and interpretation of these tests.
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