First, some background information. After an egg is fertilized by a
sperm, the egg has to travel down teh fallopian tube down to the uterus where it will implant itself and grow. After the ferilized egg implants, it starts to produce the hormone, hCG. HCG is the hormone most home pregnancy tests detect in your urine. Implantation can take up to 7-14 days after fertilization. If a home pregnancy test is used too soon (before the ferlized egg has had the change to implant), the test will give a negative result, even if you happen to be indeed pregnant; a false negative result.
Most home pregnancy tests will indicate on the package that for the most accurate result, the test should be done at least a day after the missed period. If you are a woman who have very regular cycle, it is pretty easy to know when you've missed your period. But if you're like most every other women, the day of your period may not be so easy to predict. But no worries, because if you read home pregnancy tests information pamphlets, you will find out that most of them can detect pregnancy with some degree of accuracy up to 5 days before your next expected period; keeping in mind that the closer you are to the date of your next period, the more accurate the test is.
I have also heard on recent advertisements of a home pregnancy test kit that measures the amount of a hormone variant (instead of measuring the hCG) allowing for the kit to detect pregnancy sooner than other kids.
As far as whether a name brand is better than buying a non-name brand, I really don't think it matters (especially if you've already missed a period). When I got pregnant with my son, I had a pack of 2 pregnancy tests. They both turned positive, but the line was faint. Thinking that this was due to the fact that it wasn't a popular brand, my husband and I bought 4 more brands of pregnancy tests. I used half the test the next day, and they all turned positive. I used the last couple the day after that, and they turned positive as well. In my current pregnancy, I learned my lesson and saved some money, I only bougth 2 - 2pack tests!
Reading the information print-out that comes with home pregnancy test kits will also tell you that any line, no matter how faint, is a positive result. If you use the tests only days after the implantation has occured, the hCG may not have built up in your body as of yet. If you have a 2pack test kit, use the 2nd one week later and it should turn out nice and bright.
As a last note, when you buy a pregnancy test, please read all the information and directions carefully. This will lessen your anxiety about whatever result you get. It is also important to only look at the result after the time window indcated on teh box. Oh, and make sure it isn't expired!!