TY - JOUR
T1 - Serum free light chain assay and κ/λ ratio performance in patients without monoclonal gammopathies
T2 - High false-positive rate
AU - Singh, Gurmukh
N1 - Publisher Copyright:
© 2016 American Society for Clinical Pathology, 2016. All rights reserved.
Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.
PY - 2016/8/1
Y1 - 2016/8/1
N2 - Objectives: Serum free light chain assay is a recommended screening test for monoclonal gammopathies. Anecdotal observations indicated a high rate of false-positive abnormal κ/λ ratios. This study was undertaken to ascertain the magnitude of the false-positive rate and factors contributing to the error rate. Methods: Results of serum protein electrophoresis, serum free light chains, and related tests, usually done for investigation of suspected monoclonal gammopathy, were reviewed retrospectively for 270 patients and 297 observations. Results: Using the conventional κ/λ ratio, 36.4% of the ratios were abnormal, in the absence of monoclonal gammopathy. When the renal κ/λ ratio was used, the rate of abnormal κ/λ ratios was 30.1%. In patients with a γ-globulin concentration of 1.6 g/dL or more, the usual κ/λ ratio was abnormal in 54.8% of the patients. Urine protein electrophoresis was used in 53 (19.6%) instances, whereas bone marrow examination was done in 65 (24.1%) cases. Conclusions: Usual κ/λ ratio was abnormal in 36.4% of the observations in patients without evidence of monoclonal gammopathy, and an abnormal κ/λ ratio should not be used as the sole indicator for diagnosis of neoplastic proliferation of the lympho-plasmacytic system. Hypergammaglobulinemia is associated with a higher rate of false-positive abnormal κ/λ ratios. Examination of urine for monoclonal immunoglobulins may be underused, and recommendations by some to use serum free light chain assay in place of, rather than as an adjunct to, urine electrophoresis are not warranted.
AB - Objectives: Serum free light chain assay is a recommended screening test for monoclonal gammopathies. Anecdotal observations indicated a high rate of false-positive abnormal κ/λ ratios. This study was undertaken to ascertain the magnitude of the false-positive rate and factors contributing to the error rate. Methods: Results of serum protein electrophoresis, serum free light chains, and related tests, usually done for investigation of suspected monoclonal gammopathy, were reviewed retrospectively for 270 patients and 297 observations. Results: Using the conventional κ/λ ratio, 36.4% of the ratios were abnormal, in the absence of monoclonal gammopathy. When the renal κ/λ ratio was used, the rate of abnormal κ/λ ratios was 30.1%. In patients with a γ-globulin concentration of 1.6 g/dL or more, the usual κ/λ ratio was abnormal in 54.8% of the patients. Urine protein electrophoresis was used in 53 (19.6%) instances, whereas bone marrow examination was done in 65 (24.1%) cases. Conclusions: Usual κ/λ ratio was abnormal in 36.4% of the observations in patients without evidence of monoclonal gammopathy, and an abnormal κ/λ ratio should not be used as the sole indicator for diagnosis of neoplastic proliferation of the lympho-plasmacytic system. Hypergammaglobulinemia is associated with a higher rate of false-positive abnormal κ/λ ratios. Examination of urine for monoclonal immunoglobulins may be underused, and recommendations by some to use serum free light chain assay in place of, rather than as an adjunct to, urine electrophoresis are not warranted.
KW - Monoclonal gammopathy
KW - Multiple myeloma
KW - Protein electrophoresis
KW - Serum free light chain assay
KW - Serum free light chains
KW - Serum protein electrophoresis
KW - Serum protein immunofixation electrophoresis
KW - Urine protein electrophoresis
KW - Urine protein immunofixation electrophoresis
KW - ratio
KW - κ/λ
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U2 - 10.1093/ajcp/aqw099
DO - 10.1093/ajcp/aqw099
M3 - Article
C2 - 27473738
AN - SCOPUS:85013734096
SN - 0002-9173
VL - 146
SP - 207
EP - 214
JO - American Journal of Clinical Pathology
JF - American Journal of Clinical Pathology
IS - 2
ER -