What Is a Phantom hCG?
Prenatal Testing
Obie Editorial Team
A positive blood or urine pregnancy test without an intrauterine or an ectopic pregnancy is also known as a 'false positive' pregnancy test. A 'phantom hCG test' is a false positive blood (not urine) pregnancy test (usually up to about 700 mIU/cc hCG) without a pregnancy being present. A phantom blood positive pregnancy test is usually due to an error in the laboratory test. In many cases of phantom hCG the urine pregnancy test will be negative.
There are several possibilities which may produce a phantom hCG:
The phantom hCG test can be positive because the laboratory assay falsely identifies other chemicals as hCG. That is because certain chemicals (antibodies) generated in the body against other human antibodies (IgG against IgG) may bind both human and animal antibodies (heterophilic antibodies) and they may interfere with commercial hCG tests, making it falsely positive.
The paraneoplastic symptom is a condition where other parts of the body such as tumors of different body parts produce hCG, the pregnancy hormone. This could include the ovaries, uterus, or even the lung.
If you have a positive blood hCG which is not rising, the first thought is usually a miscarriage. But with the phantom hCG no pregnancy is present, and a confirmatory urine test will be negative. When a urine pregnancy test is not done in addition to a questionable quantitative blood hCG test, a patient may receive unnecessary surgery, tests, and treatments.
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A false positive hCG pregnancy test, or a positive hCG test when you are not actually pregnant rarely happens, but if it does, it can be seen both by blood and urine tests.
How early can pregnancy be detected? Learn all about pregnancy tests, false positives and false negatives, and how early you can take a pregnancy test!