A positive blood pregnancy test without a pregnancy is also known as a 'false positive' test. There are many conditions which can give a phantom false positive hcg blood or urine pregnancy test.A 'phanto
m hCG test' is a positive blood pregnancy test (usually up to about 700 mIU/cc hCG) without any of the above conditions present. The following conditions are usually present with a phantom hCG test:
- The urine pregnancy test is negative, and
- The blood hCG test is positive but usually does not rise (or drop) according to expectation and remains often below 700 mIU/mL.
The phantom hCG test is usually positive because the laboratory assay falsely identifies other chemicals as hCG.
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.
Bottom line: When a urine pregnancy test is not done in addition to a questionable quantitative blood hCG test, a patient may receive unneccessary tests and treatments.