For molecules that can be well described metrologically in the sense of the definition of measurands, and which can also be recorded analytically as individual substances, reference measurement service traceability to a metrologically sound foundation is a necessity. The establishment of traceability chains must be initiated by National Metrology Institutes (NMIs) according to applicable standards; they are at the top and leading position in this concept. If NMIs are not in the position to take up this task, alternative approaches must be sought. Traceability initiatives established by in vitro device industry or academia must meet the quality standards of NMIs. Adherence to International Organization for Standardization (ISO) procedure 15193 must be a matter of course for the establishment of reference measurement procedures (RMPs). Certified reference material (CRM) characterization must be thorough, e.g., by the application of quantitative nuclear magnetic resonance measurements and by adherence to ISO 15194. Both for RMPs and CRMs Joint Committee for Traceability in Laboratory Medicine (JCTLM) listing must be the ultimate goal. Results must be shared in a transparent manner to allow other stakeholders including NMIs to reproduce and disseminate the reference measurement procedures.

Articles

Open Access March 24, 2023

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

Judith Taibon, Tobias Santner, Neeraj Singh, Sara Cheikh Ibrahim, Galina Babitzki, Daniel Köppl, Alexander Gaudl, Andrea Geistanger, Uta Ceglarek, Manfred Rauh, Christian Geletneky

Page range: 1902-1916

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Abstract

Objectives 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.

Open Access February 15, 2023

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

Anett Engel, Lena Ruhe, Neeraj Singh, Jo Anne Wright, Franziska Liesch, Friederike Bauland, Annika I. Ostermann, Tamara Sumalowitsch, Vincent J. T. Schweinsberg, Andrea Geistanger, Johannes Kolja Hegel, Christian Geletneky, Judith Taibon

Page range: 1917-1929

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Abstract

Objectives 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.

Open Access February 14, 2023

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

Linda Salzmann, Tino Spescha, Neeraj Singh, Tobias Schierscher, Martina Bachmann, Friederike Bauland, Andrea Geistanger, Lorenz Risch, Christian Geletneky, Christoph Seger, Judith Taibon

Page range: 1930-1941

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Abstract

Objectives 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.

Open Access July 19, 2023

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

Linda Salzmann, Tino Spescha, Neeraj Singh, Anja Kobel, Vanessa Fischer, Tobias Schierscher, Friederike Bauland, Andrea Geistanger, Lorenz Risch, Christian Geletneky, Christoph Seger, Judith Taibon

Page range: 1942-1954

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Abstract

Objectives 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.

Open Access January 23, 2023

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

Linda Salzmann, Janik Wild, Neeraj Singh, Tobias Schierscher, Franziska Liesch, Friederike Bauland, Andrea Geistanger, Lorenz Risch, Christian Geletneky, Christoph Seger, Judith Taibon

Page range: 1955-1966

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Abstract

Objectives 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.

Open Access April 4, 2023

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

Anja Kobel, Tobias Schierscher, Neeraj Singh, Linda Salzmann, Franziska Liesch, Friederike Bauland, Andrea Geistanger, Lorenz Risch, Christian Geletneky, Christoph Seger, Judith Taibon

Page range: 1967-1977

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Abstract

Objectives 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.

Review

Publicly Available June 12, 2023

Recent advances of drugs monitoring in oral fluid and comparison with blood

Sara Casati, Maddalena Binda, Paola Dongiovanni, Marica Meroni, Alfonsina D’Amato, Gabriella Roda, Marica Orioli, Massimo Del Fabbro, Gianluca M. Tartaglia

Page range: 1978-1993

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Abstract

The use of alternative matrices in toxicological analyses has been on the rise in clinical and forensic settings. Oral fluid (OF), as non-invasive fluid, has attracted attention in the field of drug screening, both for therapeutic and forensic purposes, as well as for medical diagnosis, clinical management, on-site (real time) doping and for monitoring environmental exposure to toxic substances. A good correlation between OF and blood is now established for drug concentrations. Therefore, OF might be a potential substitute of blood, especially for long-term surveillance (e.g., therapeutic drugs) or to screen a large number of patients, as well as for the development of salivary point-of-care technologies. In this review, we aimed to summarize and critically evaluate the current literature that focused on the comparison of drugs detection in OF and blood specimens.

Genetics and Molecular Diagnostics

May 11, 2023

One fits all: a highly sensitive combined ddPCR/pyrosequencing system for the quantification of microchimerism after hematopoietic and solid organ transplantation

Friederike Häuser, Jens Mittler, Misra Simge Hantal, Lilli Greulich, Martina Hermanns, Annette Shrestha, Oliver Kriege, Tanja Falter, Uta D. Immel, Stephanie Herold, Brigitte Schuch, Karl J. Lackner, Heidi Rossmann, Markus Radsak

Page range: 1994-2001

Abstract

Objectives A combined digital droplet PCR (ddPCR)/pyrosequencing assay system was developed that demonstrated advantages applicable to multiple qualitative and quantitative molecular genetic diagnostic applications. Data for characterizing this combined approach for hematologic stem cell transplantation (HSCT) and allele quantification from graft-derived cell-free (cf) DNA in solid organ transplantation (SOT) is presented. Methods ddPCR and pyrosequencing assays targeting 32 SNPs/markers were established. ddPCR results from 72 gDNAs of 55 patients after allogeneic HSCT and 107 plasma-cfDNAs of 25 liver transplant recipients were compared with established methods/markers, i.e. short-tandem-repeat PCR and ALT, respectively. Results The ddPCR results were in good agreement with the established marker. The limit of detection was 0.02 % minor allele fraction. The relationship between ddPCR and STR-PCR was linear with R 2 =0.98 allowing to transfer previously established clinical STR-PCR cut-offs to ddPCR; 50-fold higher sensitivity and a variation coefficient of <2 % enable the use of low DNA concentrations (e.g. pre-sorted cells). ddPCR detected liver allograft injury at least as sensitive as ALT suggesting that ddPCR is a reliable method to monitor the transplant integrity, especially when other biomarkers are lacking (e.g. kidney). Conclusions Combining pyrosequencing for genotyping and ddPCR for minor allele quantification enhances sensitivity and precision for the patient after HSCT and SOT. The assay is designed for maximum flexibility. It is expected to be suitable for other applications (sample tracking, prenatal diagnostics, etc.).

General Clinical Chemistry and Laboratory Medicine

June 5, 2023

Design of an algorithm for the detection of intravenous fluid contamination in clinical laboratory samples

Cristian Rios Campillo, Maria Sanz de Pedro, Jose Manuel Iturzaeta, Ana Laila Qasem, Maria Jose Alcaide, Belen Fernandez-Puntero, Rubén Gómez Rioja

Page range: 2002-2009

Abstract

Objectives Contamination of blood samples from patients receiving intravenous fluids is a common error with potential risk to the patient. Algorithms based on the presence of aberrant results have been described but have the limitation that not all infusion fluids have the same composition. Our objective is to develop an algorithm based on the detection of the dilution observed on the analytes not usually included in infusion fluids. Methods A group of 89 cases was selected from samples flagged as contaminated. Contamination was confirmed by reviewing the clinical history and comparing the results with previous and subsequent samples. A control group with similar characteristics was selected. Eleven common biochemical parameters not usually included in infusion fluids and with low intraindividual variability were selected. The dilution in relation to the immediate previous results was calculated for each analyte and a global indicator, defined as the percentage of analytes with significant dilution, was calculated. ROC curves were used to define the cut-off points. Results A cut-off point of 20 % of dilutional effect requiring also a 60 % dilutional ratio achieved a high specificity (95 % CI 91–98 %) with an adequate sensitivity (64 % CI 54–74 %). The Area Under Curve obtained was 0.867 (95 % CI 0.819–0.915). Conclusions Our algorithm based on the global dilutional effect presents a similar sensitivity but greater specificity than the systems based on alarming results. The implementation of this algorithm in the laboratory information systems may facilitate the automated detection of contaminated samples.

May 12, 2023

Sex-specific disparities of serum pepsinogen I in relation to body mass index

Wenshen Xu, Bin Yang, Sheng Lin, Fuguo Zhan, Huijuan Chen, Xiaoming Qiu, Can Liu

Page range: 2010-2016

Abstract

Objectives The clinical significance of serum pepsinogen (PG) for screening gastric cancer has been a controversial topic. Serum PG I levels have been demonstrated to be correlated with age, sex, and the Helicobacter pylori ( HP ) infection. However, the underlying factors that influence serum PG I variations remain to be fully elucidated. We aimed to evaluate the impacts of sex and body mass index (BMI) on PG I in Chinese population. Methods The cross-sectional study recruited 4,299 apparently healthy participants in Fujian Province. Serum PG levels were automatically measured using ELISA method. Serum H. pylori -IgG antibody was detected by the colloidal gold immunoassay. Clinical characteristics were obtained by questionnaire. Results Totally, 2,263 participants who had tests of serum PG and anti-HP IgG antibody were enrolled. Increased BMI and serum uric acid were observed in males with low PG I value (<70 μg/L). Multiple logistic regression showed the presence of overweight was the independent risk factor for male participants with low PG I level (odds ratio [OR] 1.519; p=0.017). However, the association was not found in females. Conclusions Sex-specific association of serum low PG I with overweight was observed in the southeast coastal areas of China. Thus, effects of sexual dimorphism should not be ignored during the clinical utilization of serum PG I.

Open Access May 19, 2023

Rapid and efficient LC-MS/MS diagnosis of inherited metabolic disorders: a semi-automated workflow for analysis of organic acids, acylglycines, and acylcarnitines in urine

Barbora Piskláková, Jaroslava Friedecká, Eliška Ivanovová, Eva Hlídková, Vojtěch Bekárek, Matúš Prídavok, Aleš Kvasnička, Tomáš Adam, David Friedecký

Page range: 2017-2027

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Abstract

Objectives The analysis of organic acids in urine is an important part of the diagnosis of inherited metabolic disorders (IMDs), for which gas chromatography coupled with mass spectrometry is still predominantly used. Methods Ultra-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay for urinary organic acids, acylcarnitines and acylglycines was developed and validated. Sample preparation consists only of dilution and the addition of internal standards. Raw data processing is quick and easy using selective scheduled multiple reaction monitoring mode. A robust standardised value calculation as a data transformation together with advanced automatic visualisation tools are applied for easy evaluation of complex data. Results The developed method covers 146 biomarkers consisting of organic acids (n=99), acylglycines (n=15) and acylcarnitines (n=32) including all clinically important isomeric compounds present. Linearity with r 2 >0.98 for 118 analytes, inter-day accuracy between 80 and 120 % and imprecision under 15 % for 120 analytes were achieved. Over 2 years, more than 800 urine samples from children tested for IMDs were analysed. The workflow was evaluated on 93 patient samples and ERNDIM External Quality Assurance samples involving a total of 34 different IMDs. Conclusions The established LC-MS/MS workflow offers a comprehensive analysis of a wide range of organic acids, acylcarnitines and acylglycines in urine to perform effective, rapid and sensitive semi-automated diagnosis of more than 80 IMDs.

Open Access June 8, 2023

Persistently elevated serum concentrations of human chorionic gonadotropin (hCG)

Cristina Collazo Abal, María Covadonga Fernández Marcos, Pedro Casado Rey, María Pía Vázquez Caamaño, Henrik Alfthan, Hannu Koistinen, Ulf-Håkan Stenman

Page range: 2028-2032

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Abstract

Objectives We describe a woman with constantly elevated hCG levels in serum. Since assay interference, pregnancy or cancer did not explain the elevated levels, we measured the concentrations of hCG, its β subunit (hCGβ) and its core fragment (hCGβcf) in serum and urine using specific assays, to understand the nature of the elevated hCG levels. Methods We used 3 assays for total hCG (these assays also recognize hCGβ and to various degrees hCGβcf), 3 for intact hCG heterodimer, 3 for free hCGβ and one for hCGβcf. Results With an hCG assay detecting total hCG the serum concentrations were in the range of 150–260 IU/L for the whole study period of almost 5 years, except for a peak of 1,200 IU/L, coinciding with a spontaneous abortion. Quantitation of different forms of hCG with specific immunoassays showed that the immunoreactivity in serum consisted of hCGβ. Urine contained hCGβ and hCGβcf. Conclusions The laboratory findings are in keeping with familial hCG syndrome. However, so far the condition remains to be determined in any family members. Elevated hCG levels without any explanation are problematic as they cause suspicion of cancer or ectopic pregnancy and may lead to harmful therapy. Specific assays, as used here, will aid in diagnosis of such cases.

Reference Values and Biological Variations

May 1, 2023

Pediatric reference interval verification for 16 biochemical markers on the Alinity ci system in the CALIPER cohort of healthy children and adolescents

Mary Kathryn Bohn, Randal Schneider, Benjamin Jung, Khosrow Adeli

Page range: 2033-2040

Abstract

Objectives Special chemistry parameters are useful in the diagnosis and management of inherited disorders, liver disease, and immunopathology. Evidence-based pediatric reference intervals (RIs) are required for appropriate clinical decision-making and need to be verified as new assays are developed. This study aimed to evaluate the applicability of pediatric RIs established for biochemical markers on the ARCHITECT for use on newer Alinity assays. Methods An initial method validation was completed for 16 assays, including precision, linearity, and method comparison. Sera collected from approximately 100 healthy children and adolescents as part of the Canadian Laboratory Initiative on Pediatric Reference Intervals (CALIPER) were also analyzed on the Alinity c system. Percentage of results within established ARCHITECT RIs were calculated and considered verified if ≥90 % fell within established limits. New RIs were established for three electrolytes, glucose, and lactate wherein no data were previously reported. Results Of the 11 assays for which CALIPER pediatric RIs were previously established on ARCHITECT assays, 10 met the verification criteria. Alpha-1-antitrypsin did not meet verification criterion and a new RI was established. For the other 5 assays, de novo RIs were derived following analysis of 139–168 samples from healthy children and adolescents. None required age- and sex-partitioning. Conclusions Herein, pediatric RIs were verified or established for 16 chemistry markers in the CALIPER cohort on Alinity assays. Findings support excellent concordance between ARCHITECT and Alinity assays with one exception (alpha-1-antitrypsin) as well as robustness of age- and sex-specific patterns originally reported by CALIPER in healthy Canadian children and adolescents.

May 18, 2023

Serum GFAP – pediatric reference interval in a cohort of Danish children

Lea Tybirk, Claus Vinter Bødker Hviid, Cindy Soendersoe Knudsen, Tina Parkner

Page range: 2041-2045

Abstract

Objectives Glial fibrillary acidic protein (GFAP) in blood is an emerging biomarker of brain injury and neurological disease. Its clinical use in children is limited by the lack of a reference interval (RI). Thus, the aim of the present study was to establish an age-dependent continuous RI for serum GFAP in children. Methods Excess serum from routine allergy testing of 391 children, 0.4–17.9 years of age, was measured by a single-molecule array (Simoa) assay. A continuous RI was modelled using non-parametric quantile regression and presented both graphically and tabulated as discrete one-year RIs based on point estimates from the model. Results Serum GFAP showed a strong age-dependency with declining levels and variability from infants to adolescents. The estimated median level decreased 66 % from four months to five years of age and another 65 % from five years to 17.9 years of age. No gender difference was observed. Conclusions The study establishes an age-dependent RI for serum GFAP in children showing high levels and variability in the first years of life.

Cardiovascular Diseases

June 5, 2023

Higher troponin T serum concentrations in hospital patients without diagnosed cardiac diseases compared to a population-based cohort

Romy Gessner, Christiane Gärtner, Maria Schmidt, Felix Eckelt, Kerstin Wirkner, Markus Löffler, Tobias Uhe, Berend Isermann, Ulrich Laufs, Thorsten Kaiser, Rolf Wachter

Page range: 2046-2052

Abstract

Objectives Upper reference limits of high-sensitivity cardiac troponin T (hs-cTnT) are derived from healthy, population-based cohorts, and are frequently exceeded in hospitalized patients. In this study we aim to systematically examine the differences between in-hospital patients with no diagnosed cardiac diseases and a population-based cohort. Methods Retrospective analyses were performed in two independent cohorts. We included 5,652 participants of the prospective population-based LIFE cohort as well as 9,300 patients having been treated at our hospital between 2014 and 2021. In both cohorts, subjects with diagnosed or suspected cardiac diseases were excluded. We used Spearman’s rank correlation for correlation analyses of hs-cTnT serum concentrations and age. Sex- and age-adjusted 99th percentiles for hs-cTnT in subjects with preserved renal function were obtained in both cohorts. Results In both cohorts, hs-cTnT serum concentrations positively correlated with age. Male sex was associated with higher hs-cTnT serum concentrations. Persons treated in hospital showed significantly higher hs-cTnT concentrations in females and males aged above 50. While in the population-based cohort only 99th percentile hs-cTnT results of females aged above 70 and males aged above 60 years exceeded the assay’s upper reference limit, the 99th percentiles of in-hospital females over 40 years and males of all age groups exceeded this threshold. Conclusions Besides age and sex, hospitalization per se is correlated with higher serum concentrations of hs-cTnT in most age groups. Our results indicate, that unconditionally applying current hs-cTnT cut-offs to inpatients might overestimate myocardial infarction and potentially lead to overdiagnosis.

Infectious Diseases

Publicly Available June 9, 2023

Neopterin and kynurenine in serum and urine as prognostic biomarkers in hospitalized patients with delta and omicron variant SARS-CoV-2 infection

Lenka Kujovská Krčmová, Kateřina Matoušová, Lenka Javorská, Petr Šmahel, Mikuláš Skála, Vladimír Koblížek, Jan Škop, Dorota Turoňová, Markéta Gančarčíková, Bohuslav Melichar

Page range: 2053-2064

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Abstract

Objectives Currently, no biomarker or scoring system could clearly identify patients at risk of progression to a severe coronavirus disease (COVID)-19. Even in patients with known risk factors, the fulminant course cannot be predicted with certainty. Analysis of commonly determined clinical parameters (frailty score, age, or body mass index) together with routine biomarkers of host response (C-reactive protein and viral nucleocapsid protein) in combination with new biomarkers neopterin, kynurenine, and tryptophan, could aid in predicting the patient outcome. Methods In 2021 and 2022, urine and serum samples were prospectively collected on 1st to 4th day after hospital admission in 108 consecutive COVID-19 patients hospitalized at the University Hospital Hradec Králové, Czech Republic. Delta and omicron virus variants were studied. Neopterin, kynurenine and tryptophan were determined by liquid chromatography. Results A significant correlation was observed between urinary and serum biomarker concentrations. Urinary and serum neopterin, kynurenine and kynurenine/tryptophan ratio were significantly (p≤0.05) higher in patients who subsequently needed oxygen therapy vs. patients without oxygen therapy. These parameters were also significantly increased in patients who died during the hospitalization compared to survivors. Complex equations have been derived using the investigated biomarkers and other clinical or laboratory parameters to predict the risk of subsequent oxygen therapy or death during hospitalization. Conclusions Present data demonstrate that neopterin, kynurenine and kynurenine/tryptophan ratio in the serum or in the urine represent promising biomarkers in the management of COVID-19 that may help to guide important therapeutic decisions.

Letters to the Editor

June 1, 2023

Limitations in using the EFLM WG-A/ISO approach for assessment of reagent lot variability

Hassan Bayat, Jesper V. Johansen, Lorin Bachmann, Nils Person

Page range: e215-e217

June 1, 2023

In reply to: Limitations in using the EFLM WG-A/ISO approach for assessment of reagent lot variability

Marc H.M. Thelen, Marith van Schrojenstein Lantman, Guilaine Boursier, Florent Vanstapel, Mauro Panteghini

Page range: e218-e220

May 30, 2023

ChatGPT, critical thing and ethical practice

Amnuay Kleebayoon, Viroj Wiwanitkit

Page range: e221-e221

May 9, 2023

AI, diabetes and getting lost in translation: a multilingual evaluation of Bing with ChatGPT focused in HbA_1c

Jaume Barallat, Carolina Gómez, Ana Sancho-Cerro

Page range: e222-e224

Open Access May 16, 2023

UK diagnostics in the era of ‘permacrisis’: is it fit for purpose and able to respond to the challenges ahead?

Dimitris K. Grammatopoulos, Weizi Li, Lawrence S. Young, Neil R. Anderson

Page range: e225-e226

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May 19, 2023

The underestimated potential of vibrational spectroscopy in clinical laboratory medicine: a translational gap to close

Sander De Bruyne, Charlotte Delrue, Marijn Speeckaert

Page range: e227-e228

Open Access May 25, 2023

A universal reference interval for serum immunoglobulins free light chains may be outdated

Susan L. Fink, Mark H. Wener, Joseph W. Rudolf, Ann Nwosu, Danyel H. Tacker, Kamran Kadkhoda, Anne E. Tebo, Maria Alice V. Willrich

Page range: e229-e232

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Open Access June 1, 2023

The likelihood ratios of FIB-4-values for diagnosing advanced liver fibrosis in patients with NAFLD

Arne Åsberg, Lena Løfblad, Gunhild Garmo Hov

Page range: e233-e234

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About this journal

Objective
Clinical Chemistry and Laboratory Medicine (CCLM) publishes articles on novel teaching and training methods applicable to laboratory medicine. It is focused on basic and applied research and cutting-edge clinical laboratory medicine. CCLM is one of the leading journals in the field, with an impact factor over 8. All contributions submitted for publication in CCLM are single-blind peer reviewed by at least two experts in the field. CCLM is led by a multi-institutional editorial board. It is issued monthly, both in print and electronically. Letters to the Editor and Congress Abstracts are published online only.

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Topics

clinical biochemistry
clinical genomics and molecular biology
clinical haematology and coagulation
clinical immunology and autoimmunity
clinical microbiology
drug monitoring and analysis
evaluation of diagnostic biomarkers
disease-oriented topics (cardiovascular disease, cancer diagnostics, diabetes)
new reagents, instrumentation and technologies
new methodologies
reference materials and methods
reference values and decision limits
quality and safety in laboratory medicine
translational laboratory medicine
clinical metrology

Article formats
Research Articles, Reviews, Mini Reviews and Opinion Papers on all aspects of clinical chemistry and laboratory medicine, Guidelines and Recommendations, Point/Counterpoint Articles, Letters to the Editor, Editorials

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Volume 61 Issue 11 - Highlight Issue: The Development of Reference Measurement Procedures to Establish Metrological Traceability; Issue Editor: Ronda Greaves

Issue of Clinical Chemistry and Laboratory Medicine (CCLM)

Frontmatter

The development of reference measurement procedures to establish metrological traceability

Establishing metrological traceability for small molecule measurands in laboratory medicine

Abstract

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

Abstract

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

Abstract

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

Abstract

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

Abstract

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

Abstract

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

Abstract

Recent advances of drugs monitoring in oral fluid and comparison with blood

Abstract

One fits all: a highly sensitive combined ddPCR/pyrosequencing system for the quantification of microchimerism after hematopoietic and solid organ transplantation

Abstract

Design of an algorithm for the detection of intravenous fluid contamination in clinical laboratory samples

Abstract

Sex-specific disparities of serum pepsinogen I in relation to body mass index

Abstract

Rapid and efficient LC-MS/MS diagnosis of inherited metabolic disorders: a semi-automated workflow for analysis of organic acids, acylglycines, and acylcarnitines in urine

Abstract

Persistently elevated serum concentrations of human chorionic gonadotropin (hCG)

Abstract

Pediatric reference interval verification for 16 biochemical markers on the Alinity ci system in the CALIPER cohort of healthy children and adolescents

Abstract

Serum GFAP – pediatric reference interval in a cohort of Danish children

Abstract

Higher troponin T serum concentrations in hospital patients without diagnosed cardiac diseases compared to a population-based cohort

Abstract

Neopterin and kynurenine in serum and urine as prognostic biomarkers in hospitalized patients with delta and omicron variant SARS-CoV-2 infection

Abstract

Limitations in using the EFLM WG-A/ISO approach for assessment of reagent lot variability

In reply to: Limitations in using the EFLM WG-A/ISO approach for assessment of reagent lot variability

ChatGPT, critical thing and ethical practice

AI, diabetes and getting lost in translation: a multilingual evaluation of Bing with ChatGPT focused in HbA1c

UK diagnostics in the era of ‘permacrisis’: is it fit for purpose and able to respond to the challenges ahead?

The underestimated potential of vibrational spectroscopy in clinical laboratory medicine: a translational gap to close

A universal reference interval for serum immunoglobulins free light chains may be outdated

The likelihood ratios of FIB-4-values for diagnosing advanced liver fibrosis in patients with NAFLD

AI, diabetes and getting lost in translation: a multilingual evaluation of Bing with ChatGPT focused in HbA_1c