Which test is used to identify the presence of occult blood in stool?

Appeared in: DSSSB 14 August 2024

Explanation

The Benzidine test is a chemical method specifically designed to detect trace amounts of blood in feces that are not visible to the naked eye (occult blood).
It operates on the principle that the peroxidase enzyme present in the hemoglobin of red blood cells will catalyze the oxidation of benzidine, resulting in a distinct color change (blue) if blood is present.
This test is highly sensitive and serves as a screening tool for conditions causing gastrointestinal bleeding, such as ulcers, polyps, and colorectal cancer.

Option B: Duke's test measures bleeding time, not the presence of blood in stool. It assesses how quickly a small, standardized skin prick stops bleeding.
Option C: The Ivy test, similar to Duke's test, measures bleeding time. It is a more standardized version where an incision is made on the forearm under controlled pressure.
Option D: The Benedict test is used to detect the presence of reducing sugars, such as glucose, in the urine.

Clinical Relevance

Nursing practice connection: Knowing Diagnostic tests for identifying occult blood in stool helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Fecal Occult Blood Testing (FOBT) is a cornerstone of colorectal cancer screening programs. Nurses play a vital role in patient education regarding sample collection and dietary/medication restrictions (though modern tests have fewer restrictions).
A positive FOBT result requires prompt follow-up. The nurse's responsibility includes communicating the results to the provider and preparing the patient for subsequent diagnostic procedures like colonoscopy.
What if? If a patient has a positive FOBT but is taking iron supplements and regularly eats red meat? The nurse should recognize these as potential causes for a false-positive result with older guaiac-based tests and ensure this information is communicated to the provider. Newer immunochemical tests (FIT) are not affected by diet.

How to Approach the Question

This is a factual recall question that tests your knowledge of common diagnostic procedures.
First, identify the key concept in the question: 'identify the presence of occult blood in stool'.
Next, systematically review each option and recall its primary purpose.
Option A, Benzidine test, is for occult blood. Option B, Duke's test, and Option C, Ivy test, are for bleeding time. Option D, Benedict test, is for reducing sugars in urine.
Match the purpose from the question stem with the correct test. The Benzidine test is the only option used for detecting blood in stool.

Concept Tested & Keywords

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E6 Nursing Fundamentals Taylor p. 689-691

E6 Nursing Brunner Adult Health 3SA Vol 1 Part 2 p. 78-80

Practise the full DSSSB 14 August 2024

Attempt every question from this paper in a timed mock, then review the full solution for each one.