Abnormal blood and urine tests can provide crucial indications of amyloidosis, though a definitive diagnosis typically requires biopsy of affected tissue or bone marrow. These lab abnormalities often reflect the systemic nature of the disease, with amyloid protein deposits impacting various organs.
Key Blood Tests Indicating Amyloidosis
Blood tests are fundamental in screening for and monitoring amyloidosis, revealing distinct patterns that can prompt further investigation.
- Serum Protein Electrophoresis (SPEP) and Immunofixation Electrophoresis (IFE):
- Abnormal Finding: The presence of a monoclonal protein (M-spike), often composed of light chains (kappa or lambda), is a hallmark of AL (light chain) amyloidosis, the most common type. This M-spike represents an overproduction of a single type of antibody fragment by abnormal plasma cells.
- Serum Free Light Chain (SFLC) Assay:
- Abnormal Finding: Elevated levels of kappa or lambda free light chains, along with an abnormal kappa-to-lambda ratio, are highly suggestive of AL amyloidosis. This test is more sensitive than SPEP/IFE for detecting the abnormal light chains.
- Cardiac Biomarkers:
- Abnormal Finding: Elevated levels of N-terminal pro-B-type natriuretic peptide (NT-proBNP) and troponin (T or I) are common in cardiac amyloidosis, indicating heart strain and damage due to amyloid deposition. These markers are critical for assessing cardiac involvement and prognosis.
- Kidney Function Tests:
- Abnormal Finding: Elevated creatinine and blood urea nitrogen (BUN) levels may indicate impaired kidney function due to amyloid deposition in the glomeruli.
- Liver Function Tests:
- Abnormal Finding: Elevated alkaline phosphatase is a common finding if the liver is significantly infiltrated with amyloid. Other liver enzymes may also be mildly elevated.
- Complete Blood Count (CBC):
- Abnormal Finding: Anemia (low red blood cell count) may be present, particularly in advanced disease or if bone marrow involvement is significant.
- Erythrocyte Sedimentation Rate (ESR) and C-Reactive Protein (CRP):
- Abnormal Finding: While not specific to amyloidosis, these inflammatory markers can be elevated, reflecting the underlying chronic inflammatory state or presence of a plasma cell dyscrasia.
Key Urine Tests Indicating Amyloidosis
Urine tests are essential for detecting kidney involvement, which is frequent in amyloidosis.
- Urine Protein Electrophoresis (UPEP) and Immunofixation Electrophoresis (UIFE):
- Abnormal Finding: The presence of monoclonal light chains in the urine, often referred to as Bence Jones protein, is a strong indicator of AL amyloidosis affecting the kidneys.
- 24-Hour Urine Protein Collection:
- Abnormal Finding: Significantly elevated protein excretion (often exceeding 3.5 grams per 24 hours, indicating nephrotic range proteinuria) is a common sign of kidney damage from amyloid deposits.
Summary of Abnormal Lab Findings in Amyloidosis
The table below summarizes common abnormal lab findings associated with amyloidosis. It's important to note that specific abnormalities can vary depending on the type of amyloidosis and the organs affected.
| Lab Test Category | Specific Test | Common Abnormal Finding | Organ/System Indicated |
|---|---|---|---|
| Protein Studies | Serum Protein Electrophoresis (SPEP) | Monoclonal protein (M-spike) | Systemic, Plasma Cell Dyscrasia |
| Immunofixation Electrophoresis (IFE) | Monoclonal protein (often light chains) | Systemic, Plasma Cell Dyscrasia | |
| Serum Free Light Chain (SFLC) Assay | Elevated kappa or lambda free light chains, abnormal ratio | Systemic, Plasma Cell Dyscrasia | |
| Cardiac Markers | N-terminal pro-B-type natriuretic peptide (NT-proBNP) | Elevated | Heart |
| Troponin T or I | Elevated | Heart | |
| Kidney Function | Creatinine, Blood Urea Nitrogen (BUN) | Elevated | Kidneys |
| Liver Function | Alkaline Phosphatase | Elevated | Liver |
| Complete Blood Count | Hemoglobin | Low (anemia) | Bone Marrow, Systemic |
| Inflammatory Markers | Erythrocyte Sedimentation Rate (ESR) | Elevated | Systemic Inflammation (non-specific) |
| C-Reactive Protein (CRP) | Elevated | Systemic Inflammation (non-specific) | |
| Urine Tests | Urine Protein Electrophoresis (UPEP) | Monoclonal protein (Bence Jones protein) | Kidneys |
| Urine Immunofixation Electrophoresis (UIFE) | Monoclonal protein (Bence Jones protein) | Kidneys | |
| 24-Hour Urine Protein | High protein excretion (>3.5 g/24h is nephrotic range) | Kidneys |
These laboratory findings provide strong clues that point toward amyloidosis and help guide the diagnostic process. While blood and/or urine tests can indicate signs of the amyloid protein, only bone marrow tests or other small biopsy samples of tissue or organs can positively confirm the diagnosis of amyloidosis. For more information, please consult reputable sources like the Amyloidosis Foundation or Mayo Clinic.
