Faecal Occult Blood Test: Introduction, Principle, Procedure, Result Interpretation and Keynotes

achaurasiya

4 years ago

Faecal Occult Blood Test: Introduction, Principle, Procedure, Result Interpretation and Keynotes

Introduction of Faecal Occult Blood Test

Faecal Occult Blood Test is the common routine test in the clinical laboratory to find out the hidden blood passing in the faeces. Bleeding into the intestine may cause the passage of blood in the stool. When the bleeding is chronic with only small amounts of blood being passed with faces, the blood is not seen in the stool and is referred to as occult or hidden blood. The commonest causes of positive occult blood in tropical countries include hookworm infection and gastrointestinal disorders such as colitis, polyps, diverticulitis.

Principle of Faecal Occult Blood Test

In the ‘Faecal Occult Blood Test’, oxygen is produced when the haemoglobin in the blood comes into contact with hydrogen peroxide the liberated oxygen reacts with a chromogen ( aminopyrine) to yield a blue colour.

Test Requirements for Faecal Occult Blood Test

Hemospot kit uses the standard guaiac method to determine occult blood in the stool. Kit contains-

Test card
Developer solution-Dropper bottle containing the developer solution and it is ready to use.
Positive Control
Sample applicator
Extra need- Gloves
Waste discarding bin

Procedure of Faecal Occult Blood Test

Add stool sample on test card sample pad.
Spread it and leave it for drying.
Add developer solution.
Take result within 5 minutes.
Also, run positive control to validate the testing procedure.

Result Interpretation

Positive: Blue colouration

Negative: Absence of blue colour

Positive control: It should show blue colour.

Keynotes

Instruction to the patient-

For one day before the faecal occult blood (FOB) test, the patients should be not eating any meat and meat production.
Do not take any iron-containing drug.
Do not brush his teeth vigorously.

Older kits were cumbersome but this Hemospot kit is very simple to handle.
Hemospot kit is very convenient since no sample preparation is required and also kit is storable at room temperatures for 2 years.
Cortez Fecal Occult Blood RapiCard Insta Test uses the technology of immunochromatographic sandwich assay and thus its sensitivity and specificity are higher than the conventional guaiac method.
Faecal Occult Blood test in short is also called FOB test.
In the case of the positive test, additional testing such as a colonoscopy is needed to locate the source of the bleeding.