The probability of a false positive in a chemical assay for a drug or poison (something appearing to show up when it isn't really there) is reasonably well known.

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Geron and GE Healthcare, a division of General Electric, are developing and commercializing cellular assay products derived from human embryonic stem cells for use in drug discovery, development and toxicity screening.

FORBES

General Electric ( GE - news - people ), are developing and commercializing cellular assay products derived from human embryonic stem cells for use in drug discovery, development and toxicity screening.

FORBES: Four Standard-Bearers For Stem Cell Therapies