A Home Pregnancy Test, HPT, is an over the counter test that measures the hCG level in your urine. Each brand of test has a different level of sensitivity, as you can see by the chart below. Depending on how far along you are in your pregnancy determines how soon a HPT will detect the hCG levels.
When it comes to interpreting the tests, there are a few important keys to increasing accuracy and early-detection. These include:
1. Use first morning urine. Why? Because FMU will contain the highest amount of hCG. This means you can receive an accurate result sooner!
2. Hold your urine: If you need to test in the afternoon or evening, don't flush your body with liquids or urinate before testing. Hold your urine as long as (comfortably) possible. This way the hCG in the urine will not be diluted. This is a good alternative if you want to re-test or if you cannot use FMU.
3. Adhere to the test reaction time! If you go to Drugstore.com or any product review site, you will find many women complaining about false positive pregnancy tests. Actually, a false positive pregnancy test is quite rare. What may be happening here is that the test user is trying to read the test after the given reaction time specified by the manufacturer. The fact is, every test has a time interval that must be respected, typically between five and ten minutes. Any result determined after the reaction time should be disregarded or considered "invalid". Why? Two reasons. The first is that a test will become increasingly more sensitive over time and may indicate a very faint test line based on naturally levels of hCG (present in non-pregnant women and even men!). Second, sometimes the chemical composition of urine will cause a ghost line or evaporation line. Typically colorless, an evaporation line will only appear well after the given reaction time of the test. In other words, if you see an evaporation line, you should not be looking at the test anyway! In other words, if you see a ghost line, this is not a false positive, as the test reaction time has passed and the any result should be considered not valid.
A false negative pregnancy test is typically due to situations where the user is testing to early or there is not enough hCG in the urine sample. To avoid false negative results, observe tips one and two, and follow the testing guidelines of the manufacturer. There may also be instances where hCG levels differ among women. In other words, for women the rate of hCG production is slower, meaning that she may need to wait a few days longer before receiving a positive result. Also, implantation may occur later, which will also result in a bit of a delay in determining a positive result.