From the Guidelines
Laboratory tests for Amyloidosis include serum free light chains, serum immunofixation electrophoresis (IFE), urine IFE, and bone marrow biopsy to identify a monoclonal light chain in the blood or urine and clonal proliferation of lambda or kappa-producing plasma cells [ 1 ].
Key Laboratory Tests
- Serum free light chains: to identify abnormal kappa and lambda immunoglobulin free light chain ratios [ 1 ]
- Serum and urine immunofixation electrophoresis (IFE): to detect and characterize monoclonal proteins [ 1 ]
- Bone marrow biopsy: to assess clonal plasma cell proliferation and identify the type of amyloidosis [ 1 ]
- Mass spectrometry-based analysis (LC-MS/MS): the gold standard for tissue diagnosis, with a reported sensitivity of 88% and specificity of 96% [ 1 ]
Additional Tests
- Congo red staining: to detect amyloid deposits in tissue biopsies [ 1 ]
- NT-proBNP and Troponin T: cardiac biomarkers used for staging and diagnosis [ 1 ]
- Abdominal fat aspirate: a simple, less-invasive procedure with excellent sensitivity for AL amyloidosis [ 1 ]
From the Research
Laboratory Tests for Amyloidosis
The diagnosis of amyloidosis involves a combination of laboratory tests and tissue biopsies. Some of the key laboratory tests used to diagnose amyloidosis include:
- Serum immunofixation electrophoresis (IFE) to detect light-chain clonality 2
- Urine IFE to detect light-chain clonality 2
- Serum protein electrophoresis (PEP) to detect abnormal protein levels 2
- Urine PEP to detect abnormal protein levels 2
- Serum free light chain (SFLC) ratio to detect light-chain clonality 2
- Bone marrow immunohistochemistry (IHC) to detect light-chain clonality 2
- Flow cytometric (FCM) assay to detect aberrant plasma cells 2
- Congo red staining of bone marrow samples to identify amyloid deposits 2, 3
- Periodic acid-Schiff (PAS) staining to diagnose Congo red-negative amyloidosis 2
- Laser capture microdissection and tandem mass spectrometry (LCM-MS) to identify the amyloidogenic protein 3, 4
- Immunofluorescence and immunohistochemistry to type the amyloid protein 4
- Genetic mutational analysis to rule in or out hereditary amyloidoses 4
Amyloid Typing
Amyloid typing is essential to determine the specific type of amyloidosis, as different types have different treatments. The most advanced technique for amyloid typing is laser microdissection followed by mass spectrometry, which can directly identify proteins with or without mutations 4. Other methods, such as immunofluorescence and immunohistochemistry, are also used, but have limitations in terms of availability, specificity, and sensitivity of commercial antibodies 4.
Imaging Studies
Imaging studies, such as cardiac MRI with gadolinium and (123)I-labeled SAP scintigraphy, can assist in the evaluation of patients with known amyloidosis and can also detect amyloid in patients previously unsuspected of the disease 4, 5. Echocardiography and cardiac magnetic resonance imaging are also used to diagnose cardiac amyloidosis 5.