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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...

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Autores principales: 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
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2022
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.
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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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