Why Orange juice causes False Negative Guaiac Test

  1. help!!! i am studying for nclex and i bumped into a question that orange juice or vitamin c should be avoided when performing a guaiac test because it gives a false negative reading. does anybody know the rationale' for this? why false-negative?
    Last edit by NGACAYAN-CORTES on May 25, '04
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  2. 4 Comments

  3. by   psychomachia
    Quote from ngacayan-cortes
    help!!! i am studying for nclex and i bumped into a question that orange juice or vitamin c should be avoided when performing a guaiac test because it gives a false negative reading. does anybody know the rationale' for this? why false-negative?
    hemoglobin contains pseudoperoxidase, which causes guaiac to turn blue in the presence of hydrogen peroxide (developer). vitamin c interferes with the psuedoperoxidase in the hemoglobin, thus causing a false negative reaction.

    kind of like a "pseudoperoxidase blocker."
  4. by   psychomachia
    Now we know why nurses need to take chemistry...
  5. by   Nurse Ratched
    Very interesting! Thanks .
  6. by   ceecel.dee
    Never heard this! I've learned something today!

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