1. How does the test that I do at home myself compare with the results of a test done in a lab?
Home pregnancy testing is very similar to qualitative urine hCG testing in the laboratory, but there are factors surrounding its use that are important to note.
Home pregnancy tests come with very specific instructions that must be followed explicitly. If you are using a home pregnancy test kit, always follow the instructions provided extremely carefully.
Home pregnancy tests are sometimes performed too soon after the missed menstrual cycle (period) to result in a positive test - it takes 10 days after conception before the presence of hCG can be detected by the urine test. That is why a home test is sometimes negative when the test done by your doctor is positive - the doctor's test is often done several days later when hCG levels have become detectable.
All urine qualitative hCG tests should, if possible, be done on a first morning urine sample. Urine becomes much more dilute after ingestion of liquids (tea, coffee, juice, water, etc.) and urine hCG concentrations may become too low to register as positive.
Generally, when used correctly, the home pregnancy test should produce the same result as the urine hCG test done by your doctor. Quantitative blood testing for hCG is more sensitive than urine hCG testing, so sometimes a blood test will indicate pregnancy when the urine test is negative. Quantitative hCG testing requires a blood sample and testing must be performed in a laboratory.
An ectopic pregnancy is the condition when the fertilised ovum (blastocyst) implants somewhere other than in the uterus. This is a serious condition needing immediate treatment. Patients with ectopic pregnancies often have abdominal pain and uterine bleeding. Usually, abnormal levels of hCG are produced in ectopic pregnancies with slower-than-normal rates of increase.
Gestational trophoblastic disease refers to a group of disorders that can affect a woman’s uterus. The disorders include benign tumours, molar pregnancies and malignant choriocarcinoma. The tumours start in the trophoblast cells (cells that form the placenta in a normal pregnancy). Blood hCG tests can be used to help to diagnose and monitor gestational trophoblastic disease.
4. When is a blood hCG test requested instead of a urine hCG?
The blood hCG test actually measures the amount of hCG present in the bloodstream; the urine hCG is used to detect the presence of hCG. Since hCG is not normally detected in the urine of a non-pregnant woman, the urine hCG test is usually enough to confirm a pregnancy. Sometimes, it is important to know how much hCG is present: to evaluate a suspected ectopic pregnancy, to monitor a woman following a miscarriage, to monitor the treatment of a tumour or to detect recurrence. In these circumstances, your doctor will request a blood hCG test.
5. How many days after a miscarriage would it take for a urine pregnancy test to show a negative result?
Urine hCG disappears at about the same rate as blood hCG, which can take anywhere from 9 to 35 days, with a median of 19 days. However, the timeframe for when an hCG result will be negative is dependent on what the hCG level was at the time of the miscarriage. Frequently miscarriages are monitored with quantitative blood hCG testing. If the levels of hCG do not fall to undetectable levels, some hCG-producing tissue may remain and have to be removed.
This article was last reviewed on 19 December 2013. | This article was last modified on 20 December 2013.
The review date indicates when the article was last reviewed from beginning to end to ensure that it reflects the most current science. A review may not require any modifications to the article, so the two dates may not always agree.
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