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Inter-Laboratory Concordance of Cerebrospinal Fluid and Serum Kappa Free Light Chain Measurements
The kappa index (K-Index), calculated by dividing the cerebrospinal fluid (CSF)/serum kappa free light chain (KFLC) ratio by the CSF/serum albumin ratio, is gaining increasing interest as a marker of intrathecal immunoglobulin synthesis. However, data on inter-laboratory agreement of these measures...
Autores principales: | , , , , , , , , , , , , , , , , , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
MDPI
2022
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9138559/ https://www.ncbi.nlm.nih.gov/pubmed/35625604 http://dx.doi.org/10.3390/biom12050677 |
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author | Natali, Patrizia Bedin, Roberta Bernardi, Gaetano Corsini, Elena Cocco, Eleonora Schirru, Lucia Crespi, Ilaria Lamonaca, Marta Sala, Arianna Nicolò, Cinzia Di Filippo, Massimiliano Villa, Alfredo Nociti, Viviana De Michele, Teresa Cavalla, Paola Caropreso, Paola Vitetta, Francesca Cucinelli, Maria Rosaria Gastaldi, Matteo Trenti, Tommaso Sola, Patrizia Ferraro, Diana |
author_facet | Natali, Patrizia Bedin, Roberta Bernardi, Gaetano Corsini, Elena Cocco, Eleonora Schirru, Lucia Crespi, Ilaria Lamonaca, Marta Sala, Arianna Nicolò, Cinzia Di Filippo, Massimiliano Villa, Alfredo Nociti, Viviana De Michele, Teresa Cavalla, Paola Caropreso, Paola Vitetta, Francesca Cucinelli, Maria Rosaria Gastaldi, Matteo Trenti, Tommaso Sola, Patrizia Ferraro, Diana |
author_sort | Natali, Patrizia |
collection | PubMed |
description | The kappa index (K-Index), calculated by dividing the cerebrospinal fluid (CSF)/serum kappa free light chain (KFLC) ratio by the CSF/serum albumin ratio, is gaining increasing interest as a marker of intrathecal immunoglobulin synthesis. However, data on inter-laboratory agreement of these measures is lacking. The aim was to assess the concordance of CSF and serum KFLC measurements, and of K-index values, across different laboratories. KFLC and albumin of 15 paired CSF and serum samples were analyzed by eight participating laboratories. Four centers used Binding Site instruments and assays (B), three used Siemens instruments and assays (S), and one center used a Siemens instrument with a Binding Site assay (mixed). Absolute individual agreement was calculated using a two-way mixed effects intraclass correlation coefficient (ICC). Cohen’s kappa coefficient (k) was used to measure agreement on positive (≥5.8) K-index values. There was an excellent agreement in CSF KFLC measurements across all laboratories (ICC (95% confidence interval): 0.93 (0.87–0.97)) and of serum KFLC across B and S laboratories (ICC: 0.91 (0.73–0.97)), while ICC decreased (to 0.81 (0.53–0.93)) when including the mixed laboratory in the analysis. Concordance for a positive K-Index was substantial across all laboratories (k = 0.77) and within S laboratories (k = 0.71), and very good (k = 0.89) within B laboratories, meaning that patients rarely get discordant results on K-index positivity notwithstanding the testing in different laboratories and the use of different platforms/assays. |
format | Online Article Text |
id | pubmed-9138559 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2022 |
publisher | MDPI |
record_format | MEDLINE/PubMed |
spelling | pubmed-91385592022-05-28 Inter-Laboratory Concordance of Cerebrospinal Fluid and Serum Kappa Free Light Chain Measurements Natali, Patrizia Bedin, Roberta Bernardi, Gaetano Corsini, Elena Cocco, Eleonora Schirru, Lucia Crespi, Ilaria Lamonaca, Marta Sala, Arianna Nicolò, Cinzia Di Filippo, Massimiliano Villa, Alfredo Nociti, Viviana De Michele, Teresa Cavalla, Paola Caropreso, Paola Vitetta, Francesca Cucinelli, Maria Rosaria Gastaldi, Matteo Trenti, Tommaso Sola, Patrizia Ferraro, Diana Biomolecules Article The kappa index (K-Index), calculated by dividing the cerebrospinal fluid (CSF)/serum kappa free light chain (KFLC) ratio by the CSF/serum albumin ratio, is gaining increasing interest as a marker of intrathecal immunoglobulin synthesis. However, data on inter-laboratory agreement of these measures is lacking. The aim was to assess the concordance of CSF and serum KFLC measurements, and of K-index values, across different laboratories. KFLC and albumin of 15 paired CSF and serum samples were analyzed by eight participating laboratories. Four centers used Binding Site instruments and assays (B), three used Siemens instruments and assays (S), and one center used a Siemens instrument with a Binding Site assay (mixed). Absolute individual agreement was calculated using a two-way mixed effects intraclass correlation coefficient (ICC). Cohen’s kappa coefficient (k) was used to measure agreement on positive (≥5.8) K-index values. There was an excellent agreement in CSF KFLC measurements across all laboratories (ICC (95% confidence interval): 0.93 (0.87–0.97)) and of serum KFLC across B and S laboratories (ICC: 0.91 (0.73–0.97)), while ICC decreased (to 0.81 (0.53–0.93)) when including the mixed laboratory in the analysis. Concordance for a positive K-Index was substantial across all laboratories (k = 0.77) and within S laboratories (k = 0.71), and very good (k = 0.89) within B laboratories, meaning that patients rarely get discordant results on K-index positivity notwithstanding the testing in different laboratories and the use of different platforms/assays. MDPI 2022-05-07 /pmc/articles/PMC9138559/ /pubmed/35625604 http://dx.doi.org/10.3390/biom12050677 Text en © 2022 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). |
spellingShingle | Article Natali, Patrizia Bedin, Roberta Bernardi, Gaetano Corsini, Elena Cocco, Eleonora Schirru, Lucia Crespi, Ilaria Lamonaca, Marta Sala, Arianna Nicolò, Cinzia Di Filippo, Massimiliano Villa, Alfredo Nociti, Viviana De Michele, Teresa Cavalla, Paola Caropreso, Paola Vitetta, Francesca Cucinelli, Maria Rosaria Gastaldi, Matteo Trenti, Tommaso Sola, Patrizia Ferraro, Diana Inter-Laboratory Concordance of Cerebrospinal Fluid and Serum Kappa Free Light Chain Measurements |
title | Inter-Laboratory Concordance of Cerebrospinal Fluid and Serum Kappa Free Light Chain Measurements |
title_full | Inter-Laboratory Concordance of Cerebrospinal Fluid and Serum Kappa Free Light Chain Measurements |
title_fullStr | Inter-Laboratory Concordance of Cerebrospinal Fluid and Serum Kappa Free Light Chain Measurements |
title_full_unstemmed | Inter-Laboratory Concordance of Cerebrospinal Fluid and Serum Kappa Free Light Chain Measurements |
title_short | Inter-Laboratory Concordance of Cerebrospinal Fluid and Serum Kappa Free Light Chain Measurements |
title_sort | inter-laboratory concordance of cerebrospinal fluid and serum kappa free light chain measurements |
topic | Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9138559/ https://www.ncbi.nlm.nih.gov/pubmed/35625604 http://dx.doi.org/10.3390/biom12050677 |
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