Comparing Pregnancy TestsAug 18, 2000 (Updated Mar 9, 2002) Write an essay on this topic.
The Bottom Line Home pregnancy tests measure a hormone HcG which is not detectable until at least 10 days past ovulation.
Despite the small differences in mechanism, all home pregnancy tests work the same. They measure the amount of a hormone HCG (human chorionic gonadotropin) in the mother's urine. This hormone is put out my the developing embryo and will not be detectable until at least 10 days past ovulation. It is at this time that the fertilized egg implants in the womb wall and begins to be able to effect the mother's blood stream directly. Generally however, one must wait until their period is 1 day before testing at home.
Different brands however, have different sensitivity levels. The ones which will register a positive at lower amounts can be used the earliest on successfully. In fact, some can test positive even before a woman is technically "late".
Tests which measure 20 mlU are capable of showing an acurate positive reading as early as 10 days after ovulation. Keep in mind that it is always best to use first morning's urine as it will contain the highest concentration of hCG if you should, in fact, be pregnant.
If you are "sure" you are pregnant but show a negative result even after taking this precaution, try again in 2 days. The levels of hCG in the body double approximately every 48 hours. So, for example, if your hCG levels were only 15 mIU on the day you tested, in 2 days you should hit 30 mIU, and get a positive result on the most sensitive tests.
When the time comes that you are shopping for a test, keep in mind the sensitivity you need. And don't be afraid of price. Oddly enough the most sensitive test on the below list, also happens to be on of the least expensive. And the least sensitive also happens to be one of the most expensive.
HCG sensetivty in common home tests:
AimStick Pregnancy Test 20 mIU hCG
Confirm 1-Step 25 mIUs hCG
Lifesign One Step Pregnancy Test 25 mIUs hCG
One Step Be Sure Pregnancy Test 25 mIUs hCG
Clearblue Easy (U.K.) 25 mIU
CVS detects 25 mIU
Health Check 25 mIU
Insta Test hCG 25 mIU
Lifesign One-Step 25 mIU
LifeSign 1 Midstream 25 mIU
One Step Be Sure 25 mIU
E.P.T. 40 mIUs hCG
First Response (U.K.) 40 mIU
Clearblue Easy 50 mIUs hCG
Store Brands: Rite-Aid, Target 50 mIUs hCG
Answer 100 mIUs hCG
Equate (Wal-Mart) 100 mIUs hCG
First Response 100 mIUs hCG
Precise 100 mIUs hCG
QTest 100 mIUs hCG
Store Brand: Walgreens 100 mIUs hCG
Fact Plus 150-250 mIU
From personal experience I can tell you that with my last pregnancy I used a "Cornfirm" home test and received a positive result 3 days before my period was due.
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