A "Phantom hCG" is a positive blood pregnancy test without being pregnant. Patients with a phantom hCG will have a persistently and not significantly rising positive blood pregnancy test but the urine test is negative.
The reason for a phantom hCG is that some individuals react falsely positive to some substrate in the blood hCG test and thus they will display a consistently low positive blood pregnancy test even though they are not pregnant.
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.