Serum free light chain assay and κ/λ ratio performance in patients without monoclonal gammopathies

High false-positive rate

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

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.

Original languageEnglish (US)
Pages (from-to)207-214
Number of pages8
JournalAmerican Journal of Clinical Pathology
Volume146
Issue number2
DOIs
StatePublished - Aug 1 2016

Fingerprint

Paraproteinemias
Electrophoresis
Light
Urine
Serum
Bone Marrow Examination
Hypergammaglobulinemia
Globulins
Immunoglobulins
Blood Proteins
Kidney
Proteins

Keywords

  • Monoclonal gammopathy
  • Multiple myeloma
  • Protein electrophoresis
  • Serum free light chain assay
  • Serum free light chains
  • Serum protein electrophoresis
  • Serum protein immunofixation electrophoresis
  • Urine protein electrophoresis
  • Urine protein immunofixation electrophoresis
  • ratio
  • κ/λ

ASJC Scopus subject areas

  • Pathology and Forensic Medicine

Cite this

@article{3dfd5572f35f4c459d5c13810e88e8a9,
title = "Serum free light chain assay and κ/λ ratio performance in patients without monoclonal gammopathies: High false-positive rate",
abstract = "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.",
keywords = "Monoclonal gammopathy, Multiple myeloma, Protein electrophoresis, Serum free light chain assay, Serum free light chains, Serum protein electrophoresis, Serum protein immunofixation electrophoresis, Urine protein electrophoresis, Urine protein immunofixation electrophoresis, ratio, κ/λ",
author = "Gurmukh Singh",
year = "2016",
month = "8",
day = "1",
doi = "10.1093/ajcp/aqw099",
language = "English (US)",
volume = "146",
pages = "207--214",
journal = "American Journal of Clinical Pathology",
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T1 - Serum free light chain assay and κ/λ ratio performance in patients without monoclonal gammopathies

T2 - High false-positive rate

AU - Singh, Gurmukh

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.

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KW - Multiple myeloma

KW - Protein electrophoresis

KW - Serum free light chain assay

KW - Serum free light chains

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KW - Serum protein immunofixation electrophoresis

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KW - Urine protein immunofixation electrophoresis

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KW - κ/λ

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DO - 10.1093/ajcp/aqw099

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JF - American Journal of Clinical Pathology

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