Which test is done for identifying the presence of occult blood in stool?

AIIMS Bhuvneshwar NO- 2018

Medical Surgical Nursing

Easy

Appeared in: AIIMS Bhuvneshwar NO- 2018

Explanation

The Guaiac Fecal Occult Blood Test (gFOBT) is a widely used screening method for detecting hidden blood in the stool.
The test works based on the principle that the heme portion of hemoglobin has peroxidase-like activity.
When a developer solution is applied to a stool sample on guaiac paper, the heme catalyzes a reaction that turns the paper blue, indicating a positive result for blood.
This test is a crucial initial screening tool for conditions like colorectal cancer, ulcers, and other causes of gastrointestinal bleeding.

Option A: The Orthotolidine test is an older method for detecting occult blood that is now considered obsolete in most clinical settings due to its high rate of false-positive results.
Option B: The Benzidine test is no longer used because the main reagent, benzidine, is a known carcinogen and poses a significant health risk to laboratory personnel.
Option C: Fouchet's test is used to detect bile pigments (bilirubin) in urine, not blood in stool. It is a diagnostic tool for liver and biliary tract disorders.

Visual 1: Diagram - A step-by-step illustration of the Guaiac Fecal Occult Blood Test (gFOBT) procedure, showing how to apply the stool sample, add the developer, and interpret the blue color change for a positive result.
Visual 2: Comparison Chart - A chart comparing the Guaiac Fecal Occult Blood Test (gFOBT) and the Fecal Immunochemical Test (FIT), highlighting differences in principle, specificity, and patient preparation requirements.

Clinical Relevance

Nursing practice connection: Knowing Diagnostic tests for occult blood in stool helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Screening for colorectal cancer is a critical nursing responsibility. Understanding the principles and patient preparation for tests like gFOBT is essential for accurate results and early detection.
Patient education is a key nursing role. Nurses must clearly explain the dietary and medication restrictions required for the gFOBT to prevent false-positive or false-negative results, ensuring the test's validity.
What if? If a patient's gFOBT is positive, the next nursing action is to notify the healthcare provider and prepare the patient for follow-up diagnostic procedures, such as a colonoscopy, to determine the source of the bleeding.

How to Approach the Question

First, identify the key terms in the question: 'occult blood' and 'stool'. This directs you to look for a test specifically designed for hidden blood in feces.
Next, evaluate each option based on your knowledge of common laboratory tests.
Recall that the Guaiac test is a standard, well-known chemical test for this exact purpose.
Consider the other options. Recognize that Benzidine and Orthotolidine are outdated or unsafe tests for the same purpose, and Fouchet's test is for a different substance (bile) in a different sample (urine).
Confirm your choice. The Guaiac test is the most appropriate and commonly known answer among the choices for detecting occult blood in stool.

Concept Tested & Keywords

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