The ‘Starch iodine test’ is useful to diagnose:
**Core Concept**
The starch iodine test is a diagnostic tool used to detect the presence of glycogen in tissues. It involves applying a solution of iodine to a tissue sample, which turns blue-black if glycogen is present due to the formation of a complex with the iodine.
**Why the Correct Answer is Right**
The starch iodine test relies on the principle that glycogen, a complex carbohydrate stored in the liver and muscles, reacts with iodine to form a blue-black pigment. This reaction is specific to glycogen and is used to diagnose conditions such as glycogen storage diseases, where there is an accumulation of glycogen in tissues. The test is also used to assess glycogen content in various tissues, including liver and muscle biopsies.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the starch iodine test is not used to diagnose infections or inflammatory conditions.
**Option B:** This option is incorrect because the starch iodine test is not used to diagnose conditions related to protein metabolism.
**Option C:** This option is incorrect because the starch iodine test is not used to diagnose conditions related to fat metabolism.
**Clinical Pearl / High-Yield Fact**
The starch iodine test is a simple and reliable method for detecting glycogen in tissues, and it is particularly useful in diagnosing glycogen storage diseases, such as von Gierke's disease and McArdle's disease.
**Correct Answer: D. Glycogen storage diseases.**