SPEP & UPEP

Serum Protein Electrophoresis (SPEP) and Urine Protein Electrophoresis (UPEP) are diagnostic tests used to detect abnormal proteins in the blood or urine. They are particularly important in the evaluation of conditions like amyloidosis, where misfolded proteins accumulate in tissues and organs, leading to various systemic complications.

Amyloidosis:

Amyloidosis refers to a group of diseases characterized by the deposition of amyloid proteins in tissues and organs. The most common types include:

- AL amyloidosis (Primary amyloidosis): Caused by the deposition of light chains from abnormal plasma cells, often seen in connection with multiple myeloma.

- AA amyloidosis (Secondary amyloidosis): Results from chronic inflammation or infections and involves amyloid A protein.

SPEP and UPEP are crucial for detecting monoclonal protein (also called M protein) in the blood or urine, which is a hallmark of AL amyloidosis.

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Serum Protein Electrophoresis (SPEP):

1. Purpose: SPEP is used to detect abnormal proteins in the blood, particularly monoclonal immunoglobulins or light chains. These abnormal proteins are often produced by plasma cell dyscrasias such as multiple myeloma or AL amyloidosis.

2. How It Works:

- Blood serum is applied to a gel or medium, and an electric current is used to separate proteins based on their size and charge.

- Normal serum proteins, such as albumin and globulins, migrate into distinct regions on the electrophoresis gel, creating a predictable pattern.

- In conditions like AL amyloidosis, a monoclonal spike or M spike (sharp peak) is seen, indicating the presence of abnormal immunoglobulins or light chains.

3. Interpretation in Amyloidosis:

- AL amyloidosis is associated with the production of abnormal light chains (either kappa or lambda) by clonal plasma cells. These light chains can misfold and deposit as amyloid in tissues.

- SPEP may show an M spike, representing monoclonal proteins, which signals a plasma cell disorder contributing to amyloidosis.

- Sensitivity: SPEP is useful but may miss small amounts of monoclonal proteins, so it is often used alongside serum free light chain (sFLC) assays to improve detection.

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Urine Protein Electrophoresis (UPEP):

1. Purpose: UPEP is used to detect abnormal proteins in the urine, especially light chains (also called Bence Jones proteins) that are small enough to be filtered by the kidneys. This test is crucial in diagnosing plasma cell disorders and amyloidosis, particularly when SPEP alone may not detect abnormal proteins.

2. How It Works:

- A 24-hour urine sample is collected, and the proteins are separated by electrophoresis.

- Similar to SPEP, proteins in the urine are separated based on their size and charge, and the pattern is analyzed for abnormalities.

3. Interpretation in Amyloidosis:

- In AL amyloidosis, excess free light chains can be filtered by the kidneys and excreted in the urine, where they can be detected by UPEP.

- UPEP may show the presence of Bence Jones proteins (free light chains), indicating a plasma cell dyscrasia.

- Bence Jones proteinuria is often seen in conditions like multiple myeloma and AL amyloidosis, and its detection helps confirm the diagnosis.

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Combining SPEP, UPEP, and sFLC in Amyloidosis:

- SPEP and UPEP are often used in combination with the serum free light chain (sFLC) assay, which measures free kappa and lambda light chains in the blood. This test is more sensitive and helps detect low levels of monoclonal light chains that may not appear on SPEP or UPEP.

- Together, these tests help confirm the diagnosis of AL amyloidosis by detecting and characterizing abnormal monoclonal proteins (light chains) that are prone to forming amyloid deposits.

Summary:

- SPEP detects monoclonal proteins in the blood, helping identify AL amyloidosis by revealing an M spike that indicates the presence of abnormal light chains or immunoglobulins.

- UPEP detects Bence Jones proteins in the urine, which are free light chains excreted by the kidneys, further supporting the diagnosis of amyloidosis.

- These tests are critical for identifying and monitoring patients with AL amyloidosis, as well as related conditions like multiple myeloma.