What is a phantom pregnancy test?
A positive blood pregnancy test without a pregnancy is also known as a "false positive" test. A pregnancy hCG test checks for the presence of the pregnancy hormone, human chorionic gonadotropin (hCG) in your body. There are many conditions which can give a phantom false-positive hCG blood or urine pregnancy test. A "phantom hCG test" is a positive blood pregnancy test (usually up to about 700 mIU/cc hCG) without any of the above conditions present. Most women who have a positive pregnancy test are actually pregnant and only a few are not. One cause of a false positive pregnancy test is simply reading the home pregnancy test incorrectly. Pregnancy tests have certain instructions and they also differ from one another. Most manufacturers suggest you read their test after 3 minutes and to NOT READ it after 10 minutes. Once you have a negative test after 3-5 minutes throw out the test. Any positive test appearing well after that time is inaccurate and cannot be considered positive.
However, a false positive pregnancy test can also happen after an hCG injection. The reason for a phantom hCG is that some individuals react falsely positive to some substrate in the blood hCG test and thus will display a consistently low positive blood pregnancy test even though they are not pregnant, but their urine test will be negative. This phantom hCG may lead to serious misdiagnosis and intervention but can be detected with serial dilutions. Patients with phantom hCG have a positive blood hCG but a negative urine hCG test. If there is ever a question, a urine test should be done together with the blood hCG test.