Question

Specific gravity is the principle involved in the following methods of faecal examination
A. Direct smear method
B. Lanes technique
C. Agglutination test
D. Willis technique
E. Faecal trypsin test
Choose the correct answer from the options given below:

• A. A and C only
• B. A and E only
• C. B and E only
• D. B and D only

Hint:

Fecal Flotation Techniques (Specific Gravity Principle): Willis Technique (Saturated NaCl, sp. gr. 1.20), Lane's Centrifugal Flotation, Sheather's Sugar Flotation (sp. gr. 1.27).

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Qualitative and quantitative coprological flotation techniques utilize high specific gravity salt/sugar solutions to buoyant helminth ova to the surface.
Key Formula or Approach:
\[ \text{Specific Gravity of Floatation Solution (1.18--1.30)} > \text{Specific Gravity of Helminth Ova (1.05--1.18)} \]

Step 2: Detailed Explanation:
Evaluating coprological fecal examination techniques:
1. Willis Technique (Simple Flotation) (D): Uses saturated sodium chloride solution ($\text{sp. gr. } 1.20$) to float lighter nematode ova (hookworms, trichostrongyles) to the surface meniscus.
2. Lane's Technique (Centrifugal Flotation) (B): Centrifuges fecal suspensions in high-density sugar/salt solutions to rapidly concentrate floating ova.
3. Direct smear relies on direct microscopic visualization; agglutination is serological; fecal trypsin test assesses proteolytic digestion.
Therefore, flotation methods operating on specific gravity are B and D only.

Step 3: Final Answer:
Therefore, specific gravity is the principle in B and D only, corresponding to option (D).