Diagnostic Performance of Quantitative and Free Light Chain Assays in Clinical Practice Jerry A. Katzmanna, Roshini S. Abraham, Angela Dispenzieri, John A. Lust and Robert A. Kyle
Division of Clinical Biochemistry and Immunology, Department of Laboratory Medicine and Pathology, and Division of Hematology, Department of Internal Medicine, Mayo Clinic College of Medicine, Rochester, MN.
aAddress correspondence to this author at: Department of Laboratory Medicine and Pathology, Hilton 210, Mayo Clinic, Rochester, MN 55905. Fax 507-266-4088; e-mail katzmann@mayo.edu
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Background: The quantitative assay for free light chains (FLCs) is a recently introduced commercial test reported to be sensitive and specific for detecting FLC diseases such as primary systemic amyloidosis (AL), light chain deposition disease (LCDD), nonsecretory multiple myeloma (NSMM), and light chain multiple myeloma. We evaluated its diagnostic performance in clinical practice.
Methods: All FLC clinical test results generated in 2003 were abstracted from the Laboratory Information System. Diagnoses were obtained from the Dysproteinemia database and the patient medical history.
Results: In 2003, we received samples for FLC assays from 1020 Mayo Clinic patients. The majority of these patients (88%) had bone marrow-derived monoclonal plasma cell disorders (PCDs). The 121 patients who did not have monoclonal gammopathy all had FLC / ratios within the range of values obtained for a reference population in our laboratory. Among the patients with monoclonal gammopathies were patients with multiple myeloma (330), AL (269), monoclonal gammopathy of undetermined significance (114), smoldering multiple myeloma (72), plasmacytoma (22), NSMM (20), macroglobulinemia (9), LCDD (7), and a variety of other PCDs. Among the 110 AL patients who had not been previously treated and who had a FLC assay performed within 120 days of diagnosis, the FLC / ratio was positive in 91% compared with 69% for serum immunofixation electrophoresis (IFE) and 83% for urine IFE. The combination of serum IFE and serum FLC assay detected an abnormal result in 99% (109 of 110) of patients with AL
Division of Clinical Biochemistry and Immunology, Department of Laboratory Medicine and Pathology, and Division of Hematology, Department of Internal Medicine, Mayo Clinic College of Medicine, Rochester, MN.
aAddress correspondence to this author at: Department of Laboratory Medicine and Pathology, Hilton 210, Mayo Clinic, Rochester, MN 55905. Fax 507-266-4088; e-mail katzmann@mayo.edu
'//-->
.
Background: The quantitative assay for free light chains (FLCs) is a recently introduced commercial test reported to be sensitive and specific for detecting FLC diseases such as primary systemic amyloidosis (AL), light chain deposition disease (LCDD), nonsecretory multiple myeloma (NSMM), and light chain multiple myeloma. We evaluated its diagnostic performance in clinical practice.
Methods: All FLC clinical test results generated in 2003 were abstracted from the Laboratory Information System. Diagnoses were obtained from the Dysproteinemia database and the patient medical history.
Results: In 2003, we received samples for FLC assays from 1020 Mayo Clinic patients. The majority of these patients (88%) had bone marrow-derived monoclonal plasma cell disorders (PCDs). The 121 patients who did not have monoclonal gammopathy all had FLC / ratios within the range of values obtained for a reference population in our laboratory. Among the patients with monoclonal gammopathies were patients with multiple myeloma (330), AL (269), monoclonal gammopathy of undetermined significance (114), smoldering multiple myeloma (72), plasmacytoma (22), NSMM (20), macroglobulinemia (9), LCDD (7), and a variety of other PCDs. Among the 110 AL patients who had not been previously treated and who had a FLC assay performed within 120 days of diagnosis, the FLC / ratio was positive in 91% compared with 69% for serum immunofixation electrophoresis (IFE) and 83% for urine IFE. The combination of serum IFE and serum FLC assay detected an abnormal result in 99% (109 of 110) of patients with AL
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