Sometimes analysis pregnancy test tape at home may you find an imaginary line illusion as positive with the appointment menstrual cycle has come and sometimes some tests give positive results in the original there is no positive real if re-analysis under different conditions, and likewise in the results negative, which may turn into positive under different conditions or after a period of time.
So that, What are false-positive and false-negative test results?
A false-positive test result is one that shows a disease or condition is present when it is not present. A false-positive test result may suggest that a person has the disease or condition when he or she does not have it. For example, a false-positive pregnancy test result would appear to detect the substance that confirms pregnancy, when in reality the woman is not pregnant.
A false-negative test result is one that does not detect what is being tested for even though it is present. A false-negative test result may suggest that a person does not have a disease or condition being tested for when he or she does have it. For example, a false-negative pregnancy test result would be one that does not detect the substance that confirms pregnancy, when the woman really is pregnant.
Some lab tests can give you specific information. For example, your doctor may suspect you have strep throat and order a throat culture to see if streptococcus bacteria are present. A positive lab test confirms that you have strep throat and helps your doctor choose the right treatment for you.
But some tests give only a clue that must be considered with other information to support a diagnosis, identify a risk, or help choose a treatment. For example, if your cholesterol test results show you have high LDL (“bad”) cholesterol, your doctor will weigh your other risk factors for heart disease before deciding on treatment.
The source is from what explained in WEBMED website.