The accuracy of every home pregnancy test kit also depends on the factors, mentioned below:
How right you conduct the pregnancy test. Here you are to follow all the instructions exactly, and do not forget to look at the expiration date of the test.
  
When you conduct the pregnancy test. You are to be aware, that the amount of hCG in your urine grows from the least with time, though it does happen rapidly. And this is why the earlier you conduct the pregnancy test, the harder it will be to determine the presence of the hCG in your organism. The best for you would be to do the pregnancy test in about a week after your missed period, though there are tests nowadays, which are sensitive enough to work during the first day of your missed period. 

Who conducts the pregnancy test. It is common, that every pregnant woman has different amount of hCG in the urine. Thus, while some of hem may have 100%accurate results already during the first day of their missed period, while others will have to wait some time.

How soon after my missed period can I conduct a home pregnancy test and get mostly accurate results?
Most home pregnancy tests assure you that you will have the accurate result already at the first day of your missing period. However very few tests are able to provide 100% accuracy that early. The best is to wait at least one week after your missed period, and only after that, you may hope to obtain accurate answer.

However, any home pregnancy test’s accurate result depends on many factors, among which are:
How long it takes for the fertilized egg to get implanted in the uterus after ovulation. All pregnancy tests work by determining the presence or absence of the hCG in your organism, and this hormone is only produced after the fertilized egg gets attached to the wall of the uterus. As a rule it occurs somewhere in 5 – 6 days after the conception, but there are about 10% of women, in whom the embryo gets implanted much later, it is even possible after the first day of the missed period. 

How you conduct the pregnancy test you are to make sure that you follow all the directions, and do not forget to check the expiration date of the test. 

When you conduct the pregnancy test – it is clear, that the amount of hCG in the urine of every pregnant woman increases as the time goes, and the earlier after you have your period missed you conduct the home pregnancy test, the harder it will be to detect the hCG. The best for you is to wait about a week after your missed period and conduct the test, as then you will be more apt to have the accurate result. It is also important to remember, that only first morning urine should be used for the testing. 

Who conducts the pregnancy test. Every woman has her own organism, different from all others; the same with the amount of hCG in the urine at different points during early pregnancy term is different for every woman. Thus, there are women, who may obtain the accurate test result on the very day of missed period, and others will have to wait for some more time. 

The brand of the pregnancy test. There are home pregnancy tests, which are more sensitive than others may be, and they can show accurate results earlier.

I got negative result on a home pregnancy test. Is it possible for me still to be pregnant?
There is a chance for you still to be pregnant, and, besides, most home pregnancy tests’ instructions suggest repeating the test one more time in about a week.
The thing is that every woman has ovulation at different times during her menstrual cycle. Moreover, embryos get attached to the wall of the uterus at different times as well. Moreover, because every home pregnancy test begins to show accurate results only after the implantation occurs, its accuracy may vary from woman to woman. There are also many other factors, which may influence the accuracy of the home pregnancy test.

The same with your test showing you negative result. You should better repeat it in a week, and if it will say again that you are not pregnant, but you still consider that you are, the only way out for you is to apply to your doctor as soon as possible.

Is there anything, which can interfere with the home pregnancy test results?
Most medicines, over the counter as well as prescription, including birth control pills and antibiotics usually do not influence the accuracy of any home pregnancy test. Neither alcohol nor drugs influence the home pregnancy test’s result, though a woman, who plans to get pregnant, should never use neither of these substances. Only those kinds of medicine, which contain the pregnancy hormone hCG (some women may take them, while struggling with infertility), can possibly give you a false positive answer, meaning that the test says that you are pregnant, while you are not.