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

stool?

Appeared in: UPPSC 2017

Explanation

The Benzidine test is a chemical method specifically designed to detect occult (hidden) blood in stool.
The test relies on the peroxidase-like activity of the heme component of hemoglobin found in red blood cells.
When a stool sample containing blood is mixed with the benzidine reagent, it produces a distinct blue or green color, indicating a positive result.
While highly sensitive, the Benzidine test has been largely replaced in clinical practice by safer alternatives like the guaiac-based fecal occult blood test (gFOBT) and the fecal immunochemical test (FIT) because benzidine is a known carcinogen.

Option B: The Duke's test measures the time it takes for bleeding to stop from a small puncture, typically on the earlobe. It assesses capillary function and platelet plug formation, not the presence of blood in stool.
Option C: The Ivy test is another method for measuring bleeding time. It involves making a standardized incision on the forearm and measuring how long it takes to clot. It evaluates platelet function.
Option D: The Benedict test is a qualitative test used to detect the presence of reducing substances, primarily sugars like glucose, in a urine sample. It has no role in detecting blood.

Clinical Relevance

Nursing practice connection: Knowing Diagnostic tests for fecal occult blood helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Fecal occult blood testing (FOBT) is a vital, non-invasive screening tool for colorectal cancer and other causes of gastrointestinal (GI) bleeding, such as ulcers or polyps.
A positive FOBT result does not provide a diagnosis but signals the need for more definitive diagnostic procedures, most commonly a colonoscopy, to identify the source of bleeding.
Nurses play a key role in educating patients on how to properly collect stool samples and explaining any necessary dietary or medication restrictions (though restrictions are less common with modern FIT tests).

How to Approach the Question

First, identify the key concept in the question stem: the detection of 'occult blood' in 'stool'. 'Occult' means hidden.
Your goal is to find the test specifically designed for this purpose.
Evaluate each option based on your knowledge of common laboratory tests.
Recall or deduce that the Benzidine test is a chemical test for blood.
Recognize that Duke's and Ivy tests are functional tests for bleeding time (hemostasis), not for detecting blood in a sample.
Identify the Benedict test as a test for reducing sugars, typically in urine.

Concept Tested & Keywords

QO7iGh5xyq_zVTuNO7d3O3

E6 Nursing Fundamentals Taylor p. 689-691

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

Practise the full UPPSC 2017

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