**Question:** Yard-stick of detection in Snyder's test is:

A. Normal plasma proteins
B. Albumin
C. Globulin
D. Alpha-fetoprotein

**Correct Answer:** D. Alpha-fetoprotein

**Core Concept:**

Snyder's test, also known as the protein electrophoresis test, is a laboratory diagnostic procedure used to measure the levels of different plasma proteins, which can help identify various diseases and conditions. These proteins are classified into three categories: Normal plasma proteins (including albumin, globulin, and alpha-1, alpha-2, beta, and gamma globulins), which are essential for maintaining osmotic balance, clotting, and immune response.

**Why the Correct Answer is Right:**

In Snyder's test, the yardstick of detection refers to the measurement of alpha-fetoprotein (AFP), which is a specific protein produced during pregnancy and in certain pathological conditions like hepatocellular carcinoma (liver cancer). Alpha-fetoprotein levels are usually low or absent in normal plasma proteins. Therefore, the correct answer is D. Alpha-fetoprotein, as it represents a distinct component in the context of this test.

**Why Each Wrong Option is Incorrect:**

A. Normal plasma proteins: While normal plasma proteins are essential components of the test, the yardstick of detection is specifically alpha-fetoprotein (D), not the entire group of normal plasma proteins.

B. Albumin: Albumin is a normal plasma protein, but it is not the yardstick of detection in Snyder's test.

C. Globulin: Globulin is a general term for plasma proteins, but it is too broad and does not represent the specific yardstick of detection in the test.

**Clinical Pearl:**

Understanding the yardstick of detection in Snyder's test is crucial for accurate interpretation of the test results. The presence of elevated AFP levels can indicate specific diseases or conditions, allowing healthcare professionals to make an informed diagnosis and treatment plan for patients.