Guthrie test can be used for the diagnosis of ___________
**Core Concept**
The Guthrie test is a microbiological assay used for the diagnosis of certain genetic disorders. It involves the use of **bacteria** to detect the presence of specific substances in the blood. This test is primarily used for the diagnosis of **phenylketonuria (PKU)**, a genetic disorder characterized by the inability to metabolize **phenylalanine**.
**Why the Correct Answer is Right**
The correct answer is related to the diagnosis of **phenylketonuria (PKU)**. The Guthrie test detects the presence of **phenylalanine** in the blood by using **bacteria** that can only grow in the presence of this amino acid. The test is based on the principle that **phenylalanine** inhibits the growth of **bacteria**, unless it is converted to **tyrosine** by the enzyme **phenylalanine hydroxylase**, which is deficient in PKU patients.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is not related to the diagnosis of genetic disorders.
**Option B:** This option is incorrect because it is not a condition diagnosed by the Guthrie test.
**Option C:** This option is incorrect because it is not a disorder detected by this test.
**Why Each Wrong Option is Incorrect (Continued)**
**Option D:** This option is incorrect because the Guthrie test is not used for this condition.
**Clinical Pearl / High-Yield Fact**
The Guthrie test is a **screening test** for **phenylketonuria (PKU)** and is typically performed on **newborns**. Early diagnosis and treatment of PKU can prevent **mental retardation** and other complications.
**Correct Answer:** **D. Phenylketonuria**