Female on carbimazole therapy presents with sudden fever, rigors and sore throat. Which is the investigation of choice for this patient?
**Core Concept**
The patient is on carbimazole, a medication used to treat hyperthyroidism, and presents with symptoms suggestive of an infection or an adverse reaction. The **immune system** plays a crucial role in this scenario, as carbimazole can cause **agranulocytosis**, a potentially life-threatening decrease in white blood cells.
**Why the Correct Answer is Right**
Given the symptoms of fever, rigors, and sore throat in a patient on carbimazole, the most likely concern is **agranulocytosis**, which requires immediate investigation. The investigation of choice would be a **full blood count (FBC)** to check for a decrease in the white blood cell count, particularly **neutrophils**.
**Why Each Wrong Option is Incorrect**
**Option A:** Not specified, but typically, other options like blood cultures or thyroid function tests might be considered but are not the immediate choice for suspected agranulocytosis.
**Option B:** Similarly, not specified, but could involve other tests that are not as directly relevant to diagnosing agranulocytosis as a FBC.
**Option D:** Not provided, but any option not involving a direct assessment of blood cell counts would be incorrect in this context.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that patients on carbimazole should be educated to report any signs of infection immediately, as **agranulocytosis** can occur suddenly and is a medical emergency. Regular **FBC** monitoring is also crucial for early detection.
**Correct Answer:** D. Full Blood Count.