In each test there is a control and test area, in which two strips are located: one of them is a control, the manifestation of which indicates the suitability and informative nature of this test. The second strip appears only if there is hCG in the urine - it is covered with a reagent that reacts to the gonadotropin.
In each test, the instruction specifies the time, during or after which the test result should be evaluated, usually 5-10 minutes. After this time, the test becomes already uninformative. It is now possible to manifest, for example, a weak second stripe, which is not a confirmation of pregnancy.
Also, the appearance of a white or gray second strip should not be regarded as a positive result - this is the so-called drying strip (i.e., a trace from the reagent that did not show up), or similar happens if too much liquid .
It should be noted that for the positive result should take the manifestation of two clearly delineated, not blurred strips of the same size, which are necessarily located in the control and test area and are equal in color, brightness and intensity. It happens that a test performed too early can already show the presence of hCG in the urine, however, because of its very low level, the reagent appears weakly, not expressed. But without a repeat test, one should not rely on it. In the instructions to the tests they write that even a weakly expressed second strip can be regarded as a positive result. However, practice shows that this turns out to be true not always. If the second strip is too pale and blurry - most likely, it indicates that the test is unusable (it is late or defective) or incorrect testing. Also, false positive results may occur when the test is performed shortly after the abortion, against the background of taking drugs from infertility, in the presence of a woman with tumors, with impaired renal function or with the development of pathological pregnancy.
In general, a weak fuzzy second strip should be regarded as a false result and to confirm one's guesses again or another test. In this case, keep in mind that usually tests do not show pregnancy before the first day of expected, but not the coming of menstruation, although there are exceptions.
There is an opinion that a weak second stripe indicates an ectopic pregnancy - this is not entirely true. As we have already said, it is likely that the onset of pregnancy develops with disabilities. But in general, all tests determine the presence or absence of pregnancy in general, but where exactly it develops, only ultrasound can be installed.