**Question:** Confirmatory test for the diagnosis of Amyloidosis is?

**Core Concept:** Amyloidosis is a group of diseases characterized by the extracellular deposition of amyloid proteins in tissues and organs, leading to organ dysfunction and failure. Confirmatory tests help differentiate between primary and secondary amyloidosis and assess the extent of organ involvement.

**Why the Correct Answer is Right:** The correct answer is **D.** Serum free light chain (SFLC) measurement. In amyloidosis, monoclonal proteins (e.g., immunoglobulins) are produced by clonal plasma cells. These monoclonal proteins can be separated into light chains and heavy chains in serum electrophoresis. The presence of an abnormal SFLC ratio (lambda/kappa) is indicative of amyloidosis, as it suggests the presence of light chains in the blood.

**Why Each Wrong Option is Incorrect:**

A. **Option A (Serum Protein Electrophoresis):** This test detects the presence of monoclonal proteins in serum but does not differentiate between light chains or provide information on the ratio of lambda to kappa.

B. **Option B (Bone Marrow Biopsy):** While bone marrow biopsy is essential in diagnosing plasma cell dyscrasias, it is not a confirmatory test for amyloidosis diagnosis.

C. **Option C (Ultrasound):** Ultrasound is a modality used in imaging for organ assessment but is not a confirmatory test for amyloidosis diagnosis.

**Clinical Pearl:** Confirmatory tests for amyloidosis include SFLC measurement (D), serum protein electrophoresis (A), and urine electrophoresis (B). The combination of these tests aids in diagnosing and staging amyloidosis, determining the type of amyloid protein involved, and assessing the extent of organ involvement.

**Correct Answer:** D. Serum free light chain (SFLC) measurement

Amyloidosis is a disease characterized by the extracellular deposition of amyloid proteins, leading to organ dysfunction and failure. Confirmatory tests include serum free light chain (SFLC) measurement, which detects the presence of monoclonal proteins in serum and provides information on the ratio of lambda to kappa. This test aids in diagnosing and staging amyloidosis, determining the type of amyloid protein involved, and assessing the extent of organ involvement.