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  • 1
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    An isotope dilution-liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS)-based candidate reference measurement procedure (RMP) for the quantification of gabapentin in human serum and plasma
    Walter de Gruyter GmbH ; 2023
    In:  Clinical Chemistry and Laboratory Medicine (CCLM) Vol. 61, No. 11 ( 2023-10-26), p. 1955-1966
    Details
    In: Clinical Chemistry and Laboratory Medicine (CCLM), Walter de Gruyter GmbH, Vol. 61, No. 11 ( 2023-10-26), p. 1955-1966
    Abstract: To describe and validate a reference measurement procedure (RMP) for gabapentin, employing quantitative nuclear magnetic resonance (qNMR) spectroscopy to determine the absolute content of the standard materials in combination with isotope dilution-liquid chromatograph-tandem mass spectrometry (ID-LC-MS/MS) to accurately measure serum and plasma concentrations. Methods A sample preparation protocol based on protein precipitation in combination with LC-MS/MS analysis using a C8 column for chromatographic separation was established for the quantification of gabapentin. Assay validation and determination of measurement uncertainty were performed according to guidance from the Clinical and Laboratory Standards Institute, the International Conference on Harmonization, and the Guide to the expression of uncertainty in measurement. ID-LC-MS/MS parameters evaluated included selectivity, specificity, matrix effects, precision and accuracy, inter-laboratory equivalence, and uncertainty of measurement. Results The use of qNMR provided traceability to International System (SI) units. The chromatographic assay was highly selective, allowing baseline separation of gabapentin and the gabapentin-lactam impurity, without observable matrix effects. Variability between injections, preparations, calibrations, and days (intermediate precision) was 〈 2.3%, independent of the matrix, while the coefficient of variation for repeatability was 0.9–2.0% across all concentration levels. The relative mean bias ranged from −0.8–1.0% for serum and plasma samples. Passing-Bablok regression analysis indicated very good inter-laboratory agreement; the slope was 1.00 (95% confidence interval [CI] 0.98 to 1.03) and the intercept was −0.05 (95% CI -0.14 to 0.03). Pearson’s correlation coefficient was ≥0.996. Expanded measurement uncertainties for single measurements were found to be ≤5.0% (k=2). Conclusions This analytical protocol for gabapentin, utilizing traceable and selective qNMR and ID-LC-MS/MS techniques, allows for the standardization of routine tests and the reliable evaluation of clinical samples.
    Type of Medium: Online Resource
    ISSN: 1434-6621 , 1437-4331
    URL: Article
    DOI: 10.1515/cclm-2022-0998
    Language: English
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2023
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  • 2
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    An isotope dilution-liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS)-based candidate reference measurement procedure (RMP) for the quantification of methotrexate in human serum and plasma
    Walter de Gruyter GmbH ; 2023
    In:  Clinical Chemistry and Laboratory Medicine (CCLM) Vol. 61, No. 11 ( 2023-10-26), p. 1917-1929
    Details
    In: Clinical Chemistry and Laboratory Medicine (CCLM), Walter de Gruyter GmbH, Vol. 61, No. 11 ( 2023-10-26), p. 1917-1929
    Abstract: To develop an isotope dilution-liquid chromatography-tandem mass spectrometry-(ID-LC-MS/MS)-based candidate reference measurement procedure (RMP) for quantification of methotrexate in human serum and plasma. Methods Quantitative nuclear magnetic resonance (qNMR) was used to determine absolute methotrexate content in the standard. Separation was achieved on a biphenyl reversed-phase analytical column with mobile phases based on water and acetonitrile, both containing 0.1% formic acid. Sample preparation included protein precipitation in combination with high sample dilution, and method validation according to current guidelines. The following were assessed: selectivity (using analyte-spiked samples, and relevant structural-related compounds and interferences); specificity and matrix effects (via post-column infusion and comparison of human matrix vs. neat samples); precision and accuracy (in a five-day validation analysis). RMP results were compared between two independent laboratories. Measurement uncertainty was evaluated according to current guidelines. Results The RMP separated methotrexate from potentially interfering compounds and enabled measurement over a calibration range of 7.200–5,700 ng/mL (0.01584–12.54 μmol/L), with no evidence of matrix effects. All pre-defined acceptance criteria were met; intermediate precision was ≤4.3% and repeatability 1.5–2.1% for all analyte concentrations. Bias was −3.0 to 2.1% for samples within the measuring range and 0.8–4.5% for diluted samples, independent of the sample matrix. RMP results equivalence was demonstrated between two independent laboratories (Pearson correlation coefficient 0.997). Expanded measurement uncertainty of target value-assigned samples was ≤3.4%. Conclusions This ID-LC-MS/MS-based approach provides a candidate RMP for methotrexate quantification. Traceability of methotrexate standard and the LC-MS/MS platform were assured by qNMR assessment and extensive method validation.
    Type of Medium: Online Resource
    ISSN: 1434-6621 , 1437-4331
    URL: Article
    DOI: 10.1515/cclm-2022-1001
    Language: English
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2023
    detail.hit.zdb_id: 1492732-9
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  • 3
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    An isotope dilution-liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS)-based candidate reference measurement procedure for the quantification of topiramate in human serum and plasma
    Walter de Gruyter GmbH ; 2023
    In:  Clinical Chemistry and Laboratory Medicine (CCLM) Vol. 61, No. 11 ( 2023-10-26), p. 1942-1954
    Details
    In: Clinical Chemistry and Laboratory Medicine (CCLM), Walter de Gruyter GmbH, Vol. 61, No. 11 ( 2023-10-26), p. 1942-1954
    Abstract: Topiramate is an antiepileptic drug (AED) used for the monotherapy or adjunctive treatment of epilepsy and for the prophylaxis of migraine. It has several pharmacodynamic properties that contribute to both its clinically useful properties and observed adverse effects. Accurate measurement of its concentration is therefore essential for dose adjustment/optimisation of AED therapy. Our aim was to develop and validate a novel reference measurement procedure (RMP) for the quantification of topiramate in human serum and plasma. Methods An isotope dilution-liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) method in combination with a protein-precipitation-based sample preparation allows for quantification of topiramate in human serum and plasma. To assure traceability to SI units, quantitative nuclear magnetic resonance (qNMR) was applied to characterize the reference material used as primary calibrator for this RMP. Matrix effects were determined by performing a post-column infusion experiment and comparing standard line slopes. Accuracy and precision was evaluated performing an extensive five day precision experiment and measurement uncertainty was evaluated according Guide to the Expression of Uncertainty in Measurement (GUM). Results The method enabled topiramate quantification within the range of 1.20–36.0 μg/mL without interference from structurally related compounds and no evidence of a matrix effect. Intermediate precision was ≤3.2 % and repeatability was 1.4–2.5 % across all concentration levels. The relative mean bias was −0.3 to 3.5 %. Expanded measurement uncertainties for target value assignment (n=6) were found to be ≤2.9 % (k=2) independent of the concentration level and the nature of the sample. Conclusions In human serum and plasma, the RMP demonstrated high analytical performance for topiramate quantification and fulfilled the requirements on measurement uncertainty. Traceability to SI units was established by qNMR content determination of the topiramate, which was used for direct calibration of the RMP. This RMP is, therefore, fit for purpose for routine assay standardization and clinical sample evaluation.
    Type of Medium: Online Resource
    ISSN: 1434-6621 , 1437-4331
    URL: Article
    DOI: 10.1515/cclm-2022-1273
    Language: English
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2023
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  • 4
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    Multicenter evaluation of a new progastrin-releasing peptide (ProGRP) immunoassay across Europe and China
    Elsevier BV ; 2015
    In:  Clinica Chimica Acta Vol. 438 ( 2015-01), p. 388-395
    Details
    In: Clinica Chimica Acta, Elsevier BV, Vol. 438 ( 2015-01), p. 388-395
    Type of Medium: Online Resource
    ISSN: 0009-8981
    URL: Article
    DOI: 10.1016/j.cca.2014.09.015
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2015
    detail.hit.zdb_id: 1499920-1
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  • 5
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    An isotope dilution-liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS)-based candidate reference measurement procedure (RMP) for the quantification of primidone in human serum and plasma
    Walter de Gruyter GmbH ; 2024
    In:  Clinical Chemistry and Laboratory Medicine (CCLM) Vol. 0, No. 0 ( 2024-03-29)
    Details
    In: Clinical Chemistry and Laboratory Medicine (CCLM), Walter de Gruyter GmbH, Vol. 0, No. 0 ( 2024-03-29)
    Abstract: Primidone is an anticonvulsive drug used in the treatment of epilepsy and essential tremor. It offers beneficial effects in controlling seizures, but its usage is also associated with possible side effects. To ensure optimal therapy, it is crucial to measure its concentration through accurate quantification methods. Therefore, our main goal was to develop and validate a new reference measurement procedure (RMP) for accurately measuring primidone levels in human serum and plasma. Methods In our study, we focused on the separation of primidone from both known and unknown interferences using a C18 column. To achieve accurate sample preparation, we developed a protocol involving protein precipitation followed by a high dilution step. The validation of the assay and determination of measurement uncertainty were carried out following guidelines from organizations such as the Clinical and Laboratory Standards Institute, the International Conference on Harmonization, and the Guide to the Expression of Uncertainty in Measurement. These rigorous validation processes ensure the reliability and accuracy of our method for quantifying primidone levels in human serum and plasma samples. Results The RMP was shown to be highly selective and specific, with no evidence of matrix interference. It can be used to quantify primidone in the range of 0.150–30.0 μg/mL. Intermediate precision was less than 4.0 %, and repeatability CV ranged from 1.0 to 3.3 % across all concentration levels. The relative mean bias ranged from 0.1 to 3.9 % for native serum levels, and from −2.6 to 2.8 % for lithium-heparin plasma levels. The measurement uncertainties for single measurements and target value assignment were 1.5–4.1 % and 0.9–1.0 %, respectively. Conclusions In this study, we introduce an innovative LC-MS/MS-based candidate RMP specifically designed for primidone in human serum and plasma. Our RMP offers a traceable platform, facilitating the standardization of routine assays and enabling the evaluation of clinically relevant samples. With this novel approach, we aim to enhance the accuracy and reliability of primidone measurements, ultimately benefiting the field of clinical research and patient care.
    Type of Medium: Online Resource
    ISSN: 1434-6621 , 1437-4331
    URL: Article
    DOI: 10.1515/cclm-2023-1032
    Language: English
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2024
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  • 6
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    An isotope dilution-liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS)-based candidate reference measurement procedure (RMP) for the quantification of lamotrigine in human serum and plasma
    Walter de Gruyter GmbH ; 2023
    In:  Clinical Chemistry and Laboratory Medicine (CCLM) Vol. 61, No. 11 ( 2023-10-26), p. 1930-1941
    Details
    In: Clinical Chemistry and Laboratory Medicine (CCLM), Walter de Gruyter GmbH, Vol. 61, No. 11 ( 2023-10-26), p. 1930-1941
    Abstract: We developed an isotope dilution (ID)-liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based candidate reference measurement procedure (RMP) for lamotrigine in human serum and plasma, using quantitative nuclear magnetic resonance-characterized reference standards to ensure traceability to the International System of Units. Methods A sample preparation protocol based on protein precipitation combined with LC-MS/MS analysis using a C18 column for chromatographic separation was established for the quantification of lamotrigine in human serum and plasma. Assay validation was performed according to current guidelines. Spiked serum and plasma samples were used to assess selectivity and specificity; a post-column infusion experiment and comparison of standard line slopes were performed to ascertain possible matrix effects. Precision and accuracy were determined in a 5 days validation experiment. Measurement uncertainty was determined per the Guide to the Expression of Uncertainty in Measurement. Results The method allowed the quantification of lamotrigine in serum and plasma in a range of 0.600–24.0 μg/mL without any observable matrix effects. The relative mean bias (n=6) ranged from 1.7 to 3.7%; intermediate precision, including variances in between-day, -calibration, and -injection, was ≤2.4%, independent of the level and matrix. Total measurement uncertainty for a single measurement was ≤2.6%; expanded uncertainty was ≤5.2% (coverage factor k=2). Conclusions This candidate RMP based on ID-LC-MS/MS provides a traceable and reliable platform for the standardization of routine assays and the evaluation of clinical samples.
    Type of Medium: Online Resource
    ISSN: 1434-6621 , 1437-4331
    URL: Article
    DOI: 10.1515/cclm-2022-0997
    Language: English
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2023
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  • 7
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    An isotope dilution-liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS)-based candidate reference measurement procedure (RMP) for the quantification of aldosterone in human serum and plasma
    Walter de Gruyter GmbH ; 2023
    In:  Clinical Chemistry and Laboratory Medicine (CCLM) Vol. 61, No. 11 ( 2023-10-26), p. 1902-1916
    Details
    In: Clinical Chemistry and Laboratory Medicine (CCLM), Walter de Gruyter GmbH, Vol. 61, No. 11 ( 2023-10-26), p. 1902-1916
    Abstract: An isotope dilution-liquid chromatography-tandem mass spectrometry (ID-LC MS/MS)-based candidate reference measurement procedure (RMP) for aldosterone quantification in human serum and plasma is presented. Methods The material used in this RMP was characterized by quantitative nuclear magnetic resonance (qNMR) to assure traceability to SI Units. For liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis a two-dimensional heart cut LC approach, in combination with an optimal supported liquid extraction protocol, was established for the accurate analysis of aldosterone in human serum and plasma in order to minimize matrix effects and avoid the co-elution of interferences. Assay validation was performed according to current guidelines. Selectivity and specificity were assessed using spiked serum; potential matrix effects were examined by a post column infusion experiment and the comparison of standard line slopes. An extensive protocol over 5 days was applied to determine precision, accuracy and trueness. Measurement uncertainty was evaluated according to the Guide to the Expression of Uncertainty in Measurement (GUM), for which three individual sample preparations were performed on at least two different days. Results The RMP allowed aldosterone quantification within the range of 20–1,200 pg/mL without interference from structurally-related compounds and no evidence of matrix effects. Intermediate precision was ≤4.7% and repeatability was 2.8–3.7% for all analyte concentrations. The bias ranged between −2.2 and 0.5% for all levels and matrices. Total measurement uncertainties for target value assignment (n=6) were found to be ≤2.3%; expanded uncertainties were ≤4.6% (k=2) for all levels. Conclusions The RMP showed high analytical performance for aldosterone quantification in human serum and plasma. The traceability to SI units was established by qNMR content determination of aldosterone, which was utilized for direct calibration of the RMP. Thus, this candidate RMP is suitable for routine assay standardization and evaluation of clinical samples.
    Type of Medium: Online Resource
    ISSN: 1434-6621 , 1437-4331
    URL: Article
    DOI: 10.1515/cclm-2022-0996
    Language: English
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2023
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  • 8
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    An isotope dilution-liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS)-based candidate reference measurement procedure for the quantification of levetiracetam in human serum and plasma
    Walter de Gruyter GmbH ; 2023
    In:  Clinical Chemistry and Laboratory Medicine (CCLM) Vol. 61, No. 11 ( 2023-10-26), p. 1967-1977
    Details
    In: Clinical Chemistry and Laboratory Medicine (CCLM), Walter de Gruyter GmbH, Vol. 61, No. 11 ( 2023-10-26), p. 1967-1977
    Abstract: To develop an isotope dilution-liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based candidate reference measurement procedure (RMP) for levetiracetam quantification in human serum and plasma. Methods Quantitative nuclear magnetic resonance spectroscopy (qNMR) was used to characterize the RMP material to ensure traceability to SI units. To quantify levetiracetam, an LC-MS/MS method was optimized using a C8 column for chromatographic separation following protein-precipitation-based sample preparation. Spiked matrix samples of serum and plasma were used to test selectivity and specificity. Matrix effects were determined by performing a post-column infusion experiment and comparing standard line slopes. Precision and accuracy were evaluated over 5 days. Measurement uncertainty was evaluated according to the Guide to the Expression of Uncertainty in Measurement (GUM). Results The RMP was proven to be highly selective and specific with no evidence of a matrix effect, allowing for quantification of levetiracetam within the range of 1.53–90.0 μg/mL. Intermediate precision was 〈 2.2% and repeatability was 1.1–1.7% across all concentrations. The relative mean bias ranged from −2.5% to −0.3% across all levels and matrices within the measuring range. Diluted samples were found with a mean bias ranging from −0.1 to 2.9%. The predefined acceptance criterion for measurement uncertainty was met and determined for individual measurements independently of the concentration level and sample type to be ≤4.0% (k=2). Conclusions We present a novel LC-MS/MS)-based candidate RMP for levetiracetam in human serum and plasma. Its expanded measurement uncertainty of ≤4.0% meets the clinical needs in levetiracetam monitoring. Utilizing qNMR to characterize levetiracetam reference materials allowed metrological traceability to SI units.
    Type of Medium: Online Resource
    ISSN: 1434-6621 , 1437-4331
    URL: Article
    DOI: 10.1515/cclm-2022-1038
    Language: English
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2023
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  • 9
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    Statistical Methods for Monitoring the Relationship between the IFCC Reference Measurement Procedure for Hemoglobin A1c and the Designated Comparison Methods in the United States, Japan, and Sweden
    Oxford University Press (OUP) ; 2008
    In:  Clinical Chemistry Vol. 54, No. 8 ( 2008-08-01), p. 1379-1385
    Details
    In: Clinical Chemistry, Oxford University Press (OUP), Vol. 54, No. 8 ( 2008-08-01), p. 1379-1385
    Abstract: Background: The American Diabetes Association (ADA)/European Association for the Study of Diabetes (EASD)/International Diabetes Federation (IDF)/IFCC Consensus Statement on the worldwide standardization of HbA1c states that “… [HbA1c] results are to be reported world-wide in IFCC units … and derived NGSP units … , using the IFCC-NGSP master equation.” Methods: We describe statistical methods to evaluate and monitor the relationships as expressed in master equations (MEs) between the IFCC Reference Measurement procedure (IFCC-RM) and designated comparison methods (DCMs) [US National Glycohemoglobin Standardization Program (NGSP), Japanese Diabetes Society/Japanese Society for Clinical Chemistry (JDS/JSCC), and Mono-S in Sweden]. We applied these statistics, including uncertainty calculations, to 12 studies in which networks of reference laboratories participated, operating the IFCC-RM and DCMs. Results: For NGSP and Mono-S, slope, intercept, and derived percentage HbA1c at the therapeutic target show compliance with the respective MEs in all 12 studies. For JDS/JSCC, a slight deviation is seen in slope and derived percentage HbA1c in 2 of the 12 studies. Using the MEs, the uncertainty in an assigned value increases from 0.42 mmol/mol HbA1c (IFCC-RM) to 0.47 (NGSP), 0.49 (JDS/JSCC), and 0.51 (Mono-S). Conclusions: We describe sound statistical methods for the investigation of relations between networks of reference laboratories. Application of these statistical methods to the relationship between the IFCC-RM and DCMs in the US, Japan, and Sweden shows that they are suitable for the purpose, and the results support the applicability of the ADA/EASD/IDF/IFCC Consensus Statement on HbA1c measurement.
    Type of Medium: Online Resource
    ISSN: 0009-9147 , 1530-8561
    URL: Article
    DOI: 10.1373/clinchem.2008.103556
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2008
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  • 10
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    Selection of within‐run quality control rules for laboratory biomarkers
    Wiley ; 2021
    In:  Statistics in Medicine Vol. 40, No. 16 ( 2021-07-20), p. 3645-3666
    Details
    In: Statistics in Medicine, Wiley, Vol. 40, No. 16 ( 2021-07-20), p. 3645-3666
    Abstract: In order to release correct biomarker results of a laboratory test, it is a regulatory requirement to apply quality control standards for controlling analytical errors. Releasing an incorrect test result might lead to wrong diagnosis or treatment of a patient in medical decision‐making. In laboratory medicine, one of the means to control analytical errors is statistical process control procedures proposed by James O. Westgard and his coworkers nowadays known as “Westgard rules.” To judge their performance for discriminating in‐control from out‐of‐control processes, power curves are used. In this article, we describe functions for the power curves of the within‐run Westgard rules. Based on these power curves, we use a benchmark approach for selecting a quality control procedure out of the set of Westgard rules. It is shown that two graphical procedures proposed by Westgard and his coworkers can be reduced to this benchmark approach. Besides, a commonly used measure in laboratory medicine for describing out‐of‐control processes is critically examined revealing the threat of selecting too optimistic quality control rules.
    Type of Medium: Online Resource
    ISSN: 0277-6715 , 1097-0258
    URL: Issue
    URL: Article
    DOI: 10.1002/sim.v40.16
    DOI: 10.1002/sim.8987
    RVK:
    XA 10000
    Language: English
    Publisher: Wiley
    Publication Date: 2021
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