Fecal Occult Blood Test
This test is a non-evasive test that detects occult (hidden) blood in the stool samples. The occult blood test can be used to screen for any bleeding along the gastrointestinal tract and also for colon cancer.
Materials used:
Hemoccult Sensa Test Kit which comprises of 2 main component:
1) Hemocult Sensa Slides : Test cards containing the guaiac paper.
2) Hemocult Sensa Developer: A developing solution that contains a stabilized mixture of hydrogen peroxidase (42%), 80% ethyl alcohol and enhancer in aqueous solution.
Principle of Test:
The Fecal Occult Blood test is based on the oxidation of guaiac by hydrogen peroxidase into a blue compound. The heme portion of hemoglobin (if present in the fecal specimen) has peroxidase activity which will catalyze the oxidation of alpha-guaiaconic acid (an active component of the guaic paper) by hydrogen peroxidase. Hence, forming a highly conjugated blue quinone compound.
Method:
1) Label the test card with the patient's sticky label
2) Open up the test card, there will be 2 boxes A and B.
3) Using the wooden applicator, collect a small amount of fecal sample of the patient.
4) Apply a thin smear in box A.
5) Re-using the same applicator, obtain a second sample from a different part of the fecal sample. Apply a thin smear in Box B.
6) Close the cover flap and flip the card backwards.
7) Open the flap on the back of the card. There will be (i) an area to allow the developer to drop
directly on the smear, (ii) a Performance monitor area that consists of a positive and negative control.
8) Apply 2 drops of the Hemoccult SENSA Developer onto the guaiac paper directly over the smears.
9) Apply 1 drop of the Hemoccult SENSA Developer between the positive and negative performance monitor areas.
Results:
10) For the test, results must be read within 60 seconds. Any trace of of blue at or on the edge of the smear, the test is considered positive for occult blood.
11) For the performance Monitor, results have to be read within 10 seconds. If the test slide is functional, a blue colour will appear on the positive performance monitor area and no blue for the negative performance monitor area.
* In this case, the test card is functioning well, and the test is negative for occult blood. i.e the patient do not have occult blood.
Note
To avoid false positive results:
*Sample should not be collected when patient is having menstruation.
*Patient should aviod taking red meat (beef, lamb, liver) 3 days before stool collection.
*All pictures are taken and posted after permission granted by my supervisor.
Posted By: Tan Siew Ming
0702862D
hi mai!,
ReplyDeleteyour post is very interesting!!
it's also quite interesting how the card has 2 flaps and you just smear the sample on one side and the other side you just drop the sample and you have the results there..
do you have to perform this experiment in the fume hood? or u can juts perform this test in open table?
why the patient should avoid taking red meat 3 days before stool collection? would the red pigment in the meat be mistaken in blood??
opps im jiahui by the way,
ReplyDeletetg01 group 2
Hey joey!
ReplyDeleteThanks for your compliment! (:
Yep, this test is performed in the fume hood. If not, you'll be smelling the feces...=X
Patients should not consume red meat before the stool collection because red meat contains myoglobin and hemoglobin, which have peroxidase activity.
I hope i answered your questions!
Cheers,
Siew Ming
0702862D
hey siew ming.
ReplyDeleteyou perform the test in the fumehood to remove the bad odour.
if one can bear the smell, it is not needed to be conducted in the fumehood ?
furthermore, how is the stool sample collected?
Hey wess!
ReplyDeleteYep, the test can be done on the bench if one can bear the smell.. but I doubt anyone would want to inhale something unpleasant? Howeverm you also have to think for the people working around you! :D
For the stool collection part:
The bottle that is used to collect the stool sample, has a cap that has a scoop-like-thing attached to it.
If I'm not wrong, one has to place some toilet paper on the slope part of the toilet bowl and kinda aim on it... Next, they have to scoop a little of the specimen (that is on the toilet paper) using the bottle cap and put the specimen into the bottle and close it tightly.
It is important that they do not collect the specimen that has fallen into the water. =X
Thanks for you question!
Siew Ming