(2)
Interpretation.
(a) Positive. The moistened area on the filter paper around the tablet
turns blue within two minutes. The time of the appearance and the intensity of the color
developed is in proportion to the amount of blood present. Disregard any color changes
on the tablet or on the filter paper after two minutes.
(b) Negative. No blue color appears within two minutes on the
moistened portion of the filter paper around the tablet.
(3)
Precautions.
(a) Your hands, dropper, and working area must be clean and free of
traces of blood.
(b) If there is any question concerning development of the blue color
near the end of the two minute period, the test should be repeated on the same or
subsequent stool specimen.
(c) Certain plants and bacteria contain reactive substances which may
be present in a specimen in sufficient concentration to produce a false-positive reaction.
When a false-positive reaction is suspected, testing of subsequent specimens should be
performed.
b. Guaiac.
(1)
Preparation of reagents.
(a) Saturated Guaiac solution.
Guaiac crystals.................................................. 10 gm
Ethanol 95 %t .................................................... 50 ml
Mix well and store. It is stable for three to five weeks.
(b) Hydrogen peroxide. Make a three percent solution by diluting the
stock (30 percent) 1:10 with distilled water. Keep this solution in the refrigerator.
(c)
Glacial acetic acid.
(2)
Procedure.
STEP 1: Smear a solid specimen of pus on filter paper, covering an area about the size
of a quarter. Do not emulsify.
MD0841
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