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KMID : 1142020230580010071
Blood Research
2023 Volume.58 No. 1 p.71 ~ p.76
Evaluation of laboratory diagnostic tests for light-chain clonality and bone marrow findings in AL amyloidosis
Lee Tae-Geun

Park Chan-Jeoung
Kim Mi-Young
Cho Young-Uk
Jang Seong-Soo
Hwang Sang-Hyun
Lee Jung-Hee
Yoon Dok-Hyun
Abstract
Background Light-chain amyloidosis (AL) is the most common form of systemic amyloidosis. This study aimed to evaluate the usefulness of laboratory tests for light-chain clonality and bone marrow (BM) findings in AL amyloidosis.

Methods We retrospectively enrolled patients newly diagnosed with AL amyloidosis on pathological examination who underwent a BM biopsy. Laboratory test data for light-chain clonality were collected and compared. Amyloid deposits were identified with H&E, Congo red, and PAS stains.

Results We reviewed 98 patients with AL amyloidosis. Light chain clonality (¥ë, 64 cases; ¥ê, 34 cases) was detected by serum immunofixation electrophoresis (IFE) (63.3%), urine IFE (70.8%), serum protein electrophoresis (PEP) (44.9%), urine PEP (44.8%), serum free light chain (SFLC) ratio (79.5%), and BM immunohistochemistry (IHC) (85.7%). Flow cytometric (FCM) assay identified aberrant BM plasma cells in 92.9% of cases. BM amyloid deposits were identified in 35 of the 98 cases (35.7%); 71.4% (25/35) were Congo red-positive, and 100.0% (35/35) were PAS-positive.

Conclusion Laboratory tests for detecting light-chain clonality in AL amyloidosis in order of sensitivity include FCM assay for aberrant plasma cells, IHC for light chains on BM biopsy or clot section, SFLC ratio, and serum and urine IFE. Congo red staining of BM samples remains an important tool for identifying amyloid deposits in BM. Periodic acid-Schiff (PAS) staining can be useful in diagnosing some cases of Congo red-negative amyloidosis.
KEYWORD
Light-chain (AL) amyloidosis, Monoclonality, Bone marrow findings, Serum free light chain ratio, Immunohistochemistry, Flow cytometry
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