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Singh S, Khayachi A, Milnerwood AJ, DeMarco ML. Quantitative Profiling of Synuclein Species: Application to Transgenic Mouse Models of Parkinson's Disease. JOURNAL OF PARKINSONS DISEASE 2021; 10:613-621. [PMID: 32083592 DOI: 10.3233/jpd-191835] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
INTRODUCTION Improved analytical tools for detailed characterization of synucleins in pre-clinical models of Parkinson's disease (PD) and related synucleinopathies are needed. OBJECTIVE Develop a multiple reaction monitoring (MRM) liquid chromatography tandem mass spectrometry (LC-MS/MS) assay to quantify species-specific sequences and structural heterogeneity in soluble α- and β-synucleins in brain tissue. METHODS Using a proteolytic digestion workflow, the MRM LC-MS/MS method assayed six proteotypic peptides from the α-synuclein sequence; three unique to mouse or human α-synuclein and three conserved in α- and β-synuclein. For quantification, we used labeled α-synuclein as the internal standard and an external calibration curve. As proof of concept, the synuclein LC-MS/MS method was applied to brain tissue specimens from M83 transgenic PD mice, which overexpresses human α-synuclein, relative to wild-type littermate controls. RESULTS The synuclein MRM assay was linear over a wide concentration range (at least one order of magnitude). The assay had several advantages over ligand binding analytical methods, such as western blotting and enzyme-linked immunosorbent assays. These advantages included the ability to: quantify 1) total α-synuclein, 2) combined α- and β-synucleins, 3) species-specific contributions to total α-synuclein (e.g., in mice expressing both mouse and human α-synuclein), and 4) identify peptide-specific profile differences that may reflect post-translational modifications, all within a single analysis. CONCLUSION With improved and expanded analytical characteristics coupled with a streamlined sample preparation workflow, the quantitative synuclein profiling LC-MS/MS assay provides a versatile and efficient platform to characterize synuclein biology in pre-clinical models and the potential for application to human tissues and fluids.
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Singh S, DeMarco ML. In Vitro Conversion Assays Diagnostic for Neurodegenerative Proteinopathies. J Appl Lab Med 2021; 5:142-157. [PMID: 31811072 DOI: 10.1373/jalm.2019.029801] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Accepted: 10/01/2019] [Indexed: 11/06/2022]
Abstract
BACKGROUND In vitro conversion assays, including real-time quaking-induced conversion (RT-QuIC) and protein misfolding cyclic amplification (PMCA) techniques, were first developed to study the conversion process of the prion protein to its misfolded, disease-associated conformation. The intrinsic property of prion proteins to propagate their misfolded structure was later exploited to detect subfemtogram quantities of the misfolded protein present in tissues and fluids from humans and animals with transmissible spongiform encephalopathies. Currently, conversion assays are used clinically as sensitive and specific diagnostic tools for antemortem diagnosis of prion disease. CONTENT In vitro conversion assays are now being applied to the development of diagnostics for related neurodegenerative diseases, including detection of misfolded α-synuclein in Parkinson disease, misfolded amyloid-β in Alzheimer disease, and misfolded tau in Pick disease. Like the predicate prion protein in vitro conversion diagnostics, these assays exploit the ability of endogenously misfolded proteins to induce misfolding and aggregation of their natively folded counterpart in vitro. This property enables biomarker detection of the underlying protein pathology. Herein, we review RT-QuIC and PMCA for (a) prion-, (b) α-synuclein-, (c) amyloid-β-, and (d) tau-opathies. SUMMARY Although already in routine clinical use for the detection of transmissible spongiform encephalopathies, in vitro conversion assays for other neurodegenerative disorders require further development and evaluation of diagnostic performance before consideration for clinical implementation.
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Gauiran DTV, Marcon KM, DeMarco ML, Fung AWS, van der Gugten G, Mattman A, Carruthers MN, Song KW, Chen LYC. IgG4 plasma cell myeloma without clinical evidence of IgG4-related disease: a report of two cases. ACTA ACUST UNITED AC 2021; 25:335-340. [PMID: 32893754 DOI: 10.1080/16078454.2020.1815130] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Background: Serum IgG4 is typically measured to investigate for Immunoglobulin G4-related Disease (IgG4-RD), a fibroinflammatory condition associated with polyclonal increase in serum IgG4. However, increased IgG4 can also be monoclonal, and little is known about IgG4 myeloma. Methods: We describe two cases of IgG4 myeloma without clinical, radiologic, or laboratory features of IgG4-related disease. Results: An 84 year old man presented with anemia and compression fractures and a 77 year old man presented with anemia, hypercalcemia and renal failure. Both had markedly elevated monoclonal serum IgG4, 34 g/L and 48 g/L in the beta region, and increased IgG positive bone marrow plasma cells, 50% and 80%, respectively. Neither had clinical or radiological manifestations of IgG4-related disease (IgG4-RD) such as salivary or lacrimal gland swelling, autoimmune pancreatitis , or retroperitoneal fibrosis. Both cases responded well to standard myeloma therapy. The IgG4 paraprotein caused spuriously elevated beta-2 microglobulin of 45.2 mg/L in case two due to interference with the assay. Conclusion: These cases illustrate the importance of performing serum protein electrophoresis in tandem with IgG subclasses to distinguish between polyclonal and monoclonal increases in serum IgG4. The lack of typical IgG4-RD features in these two patients suggests that monoclonal elevation in serum IgG4 alone is insufficient to cause the organ damage characteristic of IgG4-RD. Larger studies of IgG myeloma subtypes are warranted to explore whether IgG1, IgG2, IgG3 and IgG4 myeloma differ in natural history and whether the interference with beta-2 microglobulin is specific to IgG4 monoclonal proteins.
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Delaby C, Teunissen CE, Alcolea D, Amar EB, Beaume A, Bedel A, Bigot‐Corbel E, Bjerke M, Blanc M, Bousiges O, Chapman MD, DeMarco ML, D'Onofrio M, Dufour‐Rainfray D, Engelborghs S, Esselmann H, Fogli A, Galloni E, Gondolf C, Grandhomme F, Grau‐Rivera O, Hart M, Jeromin A, Keshavan A, Khalil M, Koertvelyessy P, Kulczynska‐Przybik A, Laplanche J, Lleó A, Malaplate C, Mroszko B, Nogueira L, Orellana A, Otto M, Oudart J, Paquet C, Parnetti L, Perret‐Liaudet A, Poec K, Poesen K, Puig‐Pijoan A, Quadrio I, Quillard‐Muraine M, Rucheton B, Schraen S, Suárez‐Calvet M, Tsolaki M, Tumani H, Udeh‐Momoh CT, Vaudran L, Verbeek MM, Verde F, Vermunt L, Vogelgsang J, Wiltfang J, Zetterberg H, Lehmann S. International initiative for harmonization of cerebrospinal fluid diagnostic comments in Alzheimer's disease. Alzheimers Dement 2020. [DOI: 10.1002/alz.047209] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Nygaard HB, Kent BA, Stager S, Slack P, DeMarco ML, Castellano C, Rauscher A, Cunnane S, Feldman HH. A phase 1B multiple ascending dose study of the safety, tolerability, pharmacokinetics, and pharmacodynamics of a medium chain triglyceride supplement in Alzheimer’s disease. Alzheimers Dement 2020. [DOI: 10.1002/alz.037960] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Mattman A, Gilfix BM, Chen SX, DeMarco ML, Kyle BD, Parker ML, Agbor TA, Jung B, Selvarajah S, Barakauskas VE, Vaags AK, Estey MP, Nelson TN, Speevak MD. Alpha-1-antitrypsin molecular testing in Canada: A seven year, multi-centre comparison. Clin Biochem 2020; 81:27-33. [DOI: 10.1016/j.clinbiochem.2020.05.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Revised: 04/29/2020] [Accepted: 05/01/2020] [Indexed: 10/24/2022]
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DeMarco ML, Nguyen Q, Fok A, Hsiung GR, van der Gugten JG. An automated clinical mass spectrometric method for identification and quantification of variant and wild-type amyloid-β 1-40 and 1-42 peptides in CSF. ALZHEIMER'S & DEMENTIA (AMSTERDAM, NETHERLANDS) 2020; 12:e12036. [PMID: 32617385 PMCID: PMC7327131 DOI: 10.1002/dad2.12036] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Accepted: 04/06/2020] [Indexed: 11/30/2022]
Abstract
INTRODUCTION We developed an automated liquid chromatography-tandem mass spectrometry high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) method for multiplex quantification of wild-type (wt) amyloid β (Aβ) peptides 1-40 (Aβ40) and 1-42 (Aβ42) and detection of variant Aβ peptides in cerebrospinal fluid. METHODS The multiplex Aβ HPLC-MS/MS assay was validated in a clinically accredited laboratory following regulatory guidelines, with Aβ42 calibration assigned to the ERM/IFCC certified reference material; sequence variants were additionally multiplexed into the method. RESULTS Sample preparation was fully automated on a liquid handler. The assay quantified wt-Aβ42 and wt-Aβ40 and detected sequence variants, when present, within the Aβ42 sequence. DISCUSSION Extension of the HPLC-MS/MS approach for quantification of wt-Aβ42 and wt-Aβ40 to include known sequence variants increases analytical accuracy of the mass spectrometric approach and enables identification of cases of autosomal dominant Alzheimer's disease. Development of an automated workflow and selection of appropriate instrumentation enabled deployment of this method in routine clinical testing.
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Holmes DT, Romney MG, Angel P, DeMarco ML. Proteomic applications in pathology and laboratory medicine: Present state and future prospects. Clin Biochem 2020; 82:12-20. [PMID: 32442429 DOI: 10.1016/j.clinbiochem.2020.05.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 05/13/2020] [Accepted: 05/13/2020] [Indexed: 12/11/2022]
Abstract
Clinical mass spectrometry applications have traditionally focused on small molecules, particularly in the areas of therapeutic drug monitoring, toxicology, and measurement of endogenous and exogenous steroids. More recently, the use of matrix assisted laser desorption/ionization time of flight mass spectrometry for the identification of microbial pathogens has been widely implemented. Following this evolution, there has been an expanding role for the measurement of peptides and proteins in pathology and laboratory medicine. This review explores the current state of protein measurement by clinical mass spectrometry and the analytical strategies employed, as well as emerging applications in clinical chemistry, clinical microbiology and anatomical pathology.
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Mattman A, Chen LY, van der Gugten G, Chin A, Carruthers M, DeMarco ML, Holmes DT. In IgG4 related disease, elevated IgG2 is an artifact not a biomarker. Semin Arthritis Rheum 2020; 50:e8. [DOI: 10.1016/j.semarthrit.2019.08.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Accepted: 08/02/2019] [Indexed: 10/26/2022]
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Chen S, DeMarco ML, Estey MP, Kyle B, Parker ML, Agbor TA, Kawada P, Speevak M, Nelson TN, Mattman A. Null Canada: A novel α 1-antitrypsin allele with in cis variants Glu366Lys and Ile100Asn. Clin Biochem 2020; 79:23-27. [PMID: 32087139 DOI: 10.1016/j.clinbiochem.2020.02.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Revised: 01/23/2020] [Accepted: 02/18/2020] [Indexed: 11/17/2022]
Abstract
BACKGROUND α1-Antitrypsin (A1AT) deficiency predisposes patients to pulmonary disease due to inadequate protection against human neutrophil elastase released during inflammatory responses. A1AT deficiency is caused by homozygosity or compound heterozygosity for A1AT variants; individuals with A1AT deficiency most commonly have at least one Z variant allele (c.1096G > A (Glu366Lys)). Null variants that result in complete absence of A1AT in the plasma are much rarer. With one recent exception, all reported A1AT variants are characterized by a single pathogenic variant. CASE An 8 years old patient from Edmonton, Alberta, Canada, was investigated for A1AT deficiency. His A1AT phenotype was determined to be M (wild type)/Null by isoelectric focusing (IEF) but M/Z by targeted genotyping. Gene sequencing revealed two heterozygous variants: Z and Ile100Asn (c.299 T > A). The Ile100Asn substitution is predicted to disrupt the secondary structure of an α-helix in which it resides and the neighbouring tertiary structure, resulting in intracellular degradation of A1AT prior to hepatocyte secretion. METHODS Family testing was conducted to verify potential inheritance of an A1AT allele carrying the two mutations in cis, as this arrangement of the mutations would explain "Z" detection by genotyping but not by IEF. Molecular modeling was used to assess the effect of the variants on A1AT structure and stability. DISCUSSION Carrier status for a novel variant NullCanada with in cis mutations (c.[299 T > A;1096G > A], p.[(Ileu100Asn;Glu366Lys)]) was confirmed. A sibling was identified as having A1AT deficiency on the basis of compound heterozygosity for two alleles: NullCanada and the common Z allele. A separate pedigree from the Maritimes was subsequently recognized as carrying NullCanada. CONCLUSION In cis mutations such as NullCanada may be more common than previously described due to failure to detect such mutations using historical testing methods. Combined approaches that include gene sequencing and segregation studies allow recognition of rare A1AT variants, including in cis mutations.
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Forgrave LM, Ma M, Best JR, DeMarco ML. The diagnostic performance of neurofilament light chain in CSF and blood for Alzheimer's disease, frontotemporal dementia, and amyotrophic lateral sclerosis: A systematic review and meta-analysis. ALZHEIMER'S & DEMENTIA: DIAGNOSIS, ASSESSMENT & DISEASE MONITORING 2019; 11:730-743. [PMID: 31909174 PMCID: PMC6939029 DOI: 10.1016/j.dadm.2019.08.009] [Citation(s) in RCA: 90] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Introduction A systematic review and meta-analysis was performed regarding the diagnostic performance of neurofilament light chain (NfL) in CSF and blood. Methods A database search was conducted for NfL biomarker studies in the context of Alzheimer's disease (AD), frontotemporal dementia (FTD), and amyotrophic lateral sclerosis (ALS) compared with controls (i.e., cognitively unimpaired, mild cognitive impairment, or disease mimics). Results In groups with a sufficient number of studies, the performance of NfL in blood and CSF was similar. Compared with disease mimics, we observed that CSF NfL had strong discriminatory power for ALS, modest discriminatory power for FTD, and no discriminatory power for AD. NfL provided the greatest separation between ALS and cognitively unimpaired controls in both the blood and CSF, followed by FTD (CSF and blood), then AD (blood and CSF). Discussion Comparable performance of CSF and blood NfL in many groups demonstrates the promise of NfL as a noninvasive biomarker of neurodegeneration; however, its utility in clinically meaningful scenarios requires greater scrutiny. Toward clinical implementation, a more comprehensive understanding of NfL concentrations in disease subtypes with overlapping phenotypes and at defined stages of disease, and the development of a harmonization program, are warranted.
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Pobran TD, Forgrave LM, Zheng YZ, Lim JG, Mackenzie IR, DeMarco ML. Detection and characterization of TDP-43 in human cells and tissues by multiple reaction monitoring mass spectrometry. CLINICAL MASS SPECTROMETRY 2019; 14 Pt B:66-73. [DOI: 10.1016/j.clinms.2019.07.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 07/11/2019] [Accepted: 07/12/2019] [Indexed: 02/07/2023]
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Shi J, Dhaliwal P, Zi Zheng Y, Wong T, Straseski JA, Cervinski MA, Shajani-Yi Z, DeMarco ML. An Intact ACTH LC-MS/MS Assay as an Arbiter of Clinically Discordant Immunoassay Results. Clin Chem 2019; 65:1397-1404. [DOI: 10.1373/clinchem.2019.306365] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Accepted: 08/19/2019] [Indexed: 11/06/2022]
Abstract
Abstract
BACKGROUND
Measurement of plasma adrenocorticotropic hormone (ACTH) is key in the differential diagnosis of hypothalamic-pituitary-adrenal disorders. Two-site sandwich immunoassays dominate clinical testing of ACTH in North America; however, discordant results between manufacturers have been repeatedly reported. To resolve the discrepancy, we developed a liquid chromatography–tandem mass spectrometry (LC-MS/MS) assay for the intended measurand, biologically active intact ACTH (iACTH).
METHODS
The multiple reaction monitoring LC-MS/MS assay was designed to selectively measure full-length iACTH, as well as ACTH analogs and fragments (i.e., ACTH1–24 and ACTH18–39). Epitope assignment of the Roche Elecsys antibodies was performed by MALDI-TOF mass spectrometry. A method comparison between Roche Elecsys and Siemens Immulite ACTH immunoassays was performed and clinically concordant/discordant results identified. In a subset of these samples, the iACTH concentration was determined using the LC-MS/MS method.
RESULTS
The lower limit of the measuring interval of the iACTH LC-MS/MS assay was 9 pg/mL (2 pmol/L). The assay was linear from 9 to 1938 pg/mL (2 to 427 pmol/L). Epitope mapping revealed that the Roche capture and detection antibodies bound residues 9–12 and 36–39 of ACTH, respectively. The iACTH LC-MS/MS analysis demonstrated that for discordant results between 2 immunoassays studied, only the Roche results were highly positively correlated with the iACTH concentration.
CONCLUSIONS
Immunoprecipitation of biologically active ACTH molecules followed by LC-MS/MS analysis enabled selective detection of iACTH and relevant biologically active fragments in plasma. Applied to the investigation of clinically discrepant results, this method can act as an arbiter of the concentration of iACTH present.
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Fung AWS, Kohlhagen MC, DeMarco ML, Mills JR. A Rapidly Deteriorating Patient with Gross Increase in Serum Free Light Chains. Clin Chem 2019; 65:1084-1088. [PMID: 31481352 DOI: 10.1373/clinchem.2018.299008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2018] [Accepted: 01/30/2019] [Indexed: 11/06/2022]
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Duncan M, DeMarco ML. MALDI-MS: Emerging roles in pathology and laboratory medicine. CLINICAL MASS SPECTROMETRY 2019; 13:1-4. [DOI: 10.1016/j.clinms.2019.05.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Revised: 05/14/2019] [Accepted: 05/17/2019] [Indexed: 11/28/2022]
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Pobran TD, Forgrave LM, Zheng YZ, Lim JGK, Mackenzie IR, DeMarco ML. P4-483: STRUCTURAL CHARACTERIZATION OF TDP-43 IN HUMAN CELLS AND BRAIN TISSUE BY MULTIPLE-REACTION-MONITORING MASS SPECTROMETRY. Alzheimers Dement 2019. [DOI: 10.1016/j.jalz.2019.08.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Singh S, Khayachi A, Milnerwood AJ, DeMarco ML. P1-106: A MULTIPLEX MASS SPECTROMETRY METHOD FOR CHARACTERIZATION AND QUANTIFICATION OF α- AND β-SYNUCLEINS IN BRAIN TISSUE: APPLICATION TO TRANSGENIC MOUSE MODELS OF PARKINSON'S DISEASE. Alzheimers Dement 2019. [DOI: 10.1016/j.jalz.2019.06.661] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Alotaibi NM, Chen V, Hollander Z, Leipsic JA, Hague CJ, Murphy DT, DeMarco ML, FitzGerald JM, McManus BM, Ng RT, Sin DD. Phenotyping and outcomes of hospitalized COPD patients using rapid molecular diagnostics on sputum samples. Int J Chron Obstruct Pulmon Dis 2019; 14:311-319. [PMID: 30774328 PMCID: PMC6350828 DOI: 10.2147/copd.s188186] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Background Etiologies of acute exacerbations of chronic obstructive pulmonary disease (AECOPD) are heterogeneous. We phenotyped severe AECOPD based on molecular pathogen detection of sputum samples collected at hospitalization of COPD patients and determined their outcomes. Methods We phenotyped 72 sputum samples of COPD patients who were hospitalized with a primary diagnosis of AECOPD using a molecular array that detected common bacterial and viral respiratory pathogens. Based on these results, the patients were classified into positive or negative pathogen groups. The pathogen-positive group was further divided into virus or bacteria subgroups. Admission day 1 blood samples were assayed for N-terminal prohormone brain natriuretic peptide, CRP, and complete blood counts. Results A total of 52 patients had a positive result on the array, while 20 patients had no pathogens detected. The most common bacterial pathogen detected was Haemophilus influenzae and the most common virus was rhinovirus. The pathogen-negative group had the worse outcomes with longer hospital stays (median 6.5 vs 5 days for bacteria-positive group, P=0.02) and a trend toward increased 1-year mortality (P=0.052). The bacteria-positive group had the best prognosis, whereas the virus-positive group had outcomes somewhere in between the bacteria-positive and pathogen-negative groups. Conclusion Molecular diagnostics on sputum can rapidly phenotype serious AECOPD into bacteria-, virus-, or pathogen-negative groups. The bacteria-positive group appears to have the best prognosis, while pathogen-negative group has the worst. These data suggest that AECOPD is a heterogeneous event and that accurate phenotyping of AECOPD may lead to novel management strategies that are personalized and more precise.
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Zheng YZ, DeMarco ML. Corrigendum to “Manipulating trypsin digestion conditions to accelerate proteolysis and simplify digestion workflows in development of protein mass spectrometric assays for the clinical laboratory” [Clin. Mass Spectrom. 6C (2018) 1–12]. CLINICAL MASS SPECTROMETRY 2018. [DOI: 10.1016/j.clinms.2018.08.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Shi J, Zheng YZ, Sin DD, DeMarco ML. A Streamlined Method for Quantification of Apolipoprotein A1 in Human Plasma by LC-MS/MS. Clin Chem 2018; 64:1782-1784. [DOI: 10.1373/clinchem.2018.293530] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Nguyen AT, Grace van der Gugten J, Kuen Fok AC, Robin Hsiung GY, DeMarco ML. P1‐283: ROUTINE CLINICAL USE OF MASS SPECTROMETRY FOR QUANTIFICATION OF AMYLOID‐β 1‐40 AND 1‐42: PRE‐ANALYTICAL AND ANALYTICAL CONSIDERATIONS. Alzheimers Dement 2018. [DOI: 10.1016/j.jalz.2018.06.289] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Mattman A, Chen LYC, van der Gugten G, Chin A, Carruthers M, DeMarco ML, Holmes DT. Comment on: IgG4-related disease presenting with raised serum IgG2—real timeline of IgG4-RD? Rheumatology (Oxford) 2018; 57:1125-1126. [DOI: 10.1093/rheumatology/key044] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2018] [Accepted: 02/02/2018] [Indexed: 11/14/2022] Open
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van der Gugten G, DeMarco ML, Chen LYC, Chin A, Carruthers M, Holmes DT, Mattman A. Resolution of Spurious Immunonephelometric IgG Subclass Measurement Discrepancies by LC-MS/MS. Clin Chem 2018; 64:735-742. [PMID: 29352044 DOI: 10.1373/clinchem.2017.282319] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2017] [Accepted: 01/05/2018] [Indexed: 12/24/2022]
Abstract
BACKGROUND The Binding Site immunonephelometric (IN) IgG subclass reagents (IgG1, IgG2, IgG3, IgG, BSIN) are used for assessment of both immunodeficiency and IgG4-related disease (IgG4-RD). In our laboratory, suspected analytic errors were noted in patients with increases in IgG4: The sum of the individual IgG subclasses was substantially greater than the measured total IgG concentrations (unlike samples with normal IgG4), and the IgG4 concentration was always less than the IgG2 concentration. METHODS We developed a tryptic digest LC-MS/MS method to quantify IgG1, IgG2, IgG3, and IgG4 in serum. Samples with IgG4 concentrations ranging from <0.03 g/L to 32 g/L were reanalyzed by LC-MS/MS, and a subset was also reanalyzed by Siemens IN (SIN) subclass measurements. RESULTS Multivariate linear regression identified 3 subclass tests with multiple predictors of the measured subclass concentration. For these 3 subclasses, the predominant predictors were (in terms of LC-MS/MS IgG subclass measurement coefficients) BSIN IgG1 = 0.89·IgG1 + 0.4·IgG4; BSIN IgG2 = 0.94·IgG4 + 0.89·IgG2; and SIN IgG2 = 0.72·IgG2 + 0.24·IgG4. CONCLUSIONS There is apparent IgG4 cross-reactivity with select IN subclass measurements affecting tests from both vendors tested. These findings can be explained either by direct cross-reactivity of the IN reagents with the IgG4 subclass or unique physicochemical properties of IgG4 that permit nonspecific binding of IgG4 heavy chain to other IgG immunoglobulin heavy chains. Irrespective of the mechanism, the observed intermethod discrepancies support the use of LC-MS/MS as the preferred method for measurement of IgG subclasses when testing patients with suspected IgG4-RD.
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Alotaibi NM, Chen V, Hollander Z, Hague CJ, Murphy DT, Leipsic JA, DeMarco ML, FitzGerald JM, McManus BM, Ng RT, Sin DD. Phenotyping COPD exacerbations using imaging and blood-based biomarkers. Int J Chron Obstruct Pulmon Dis 2018; 13:217-229. [PMID: 29386890 PMCID: PMC5764289 DOI: 10.2147/copd.s152484] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Rationale Acute exacerbations of chronic obstructive pulmonary disease (AECOPD) are caused by a variety of different etiologic agents. Our aim was to phenotype COPD exacerbations using imaging (chest X-ray [CXR] and computed tomography [CT]) and to determine the possible role of the blood tests (C-reactive protein [CRP], the N-terminal prohormone brain natriuretic peptide [NT-proBNP]) as diagnostic biomarkers. Materials and methods Subjects who were hospitalized with a primary diagnosis of AECOPD and who had had CXRs, CT scans, and blood collection for CRP and NT-proBNP were assessed in this study. Radiologist blinded to the clinical and laboratory characteristics of the subjects interpreted their CXRs and CT images. ANOVA and Spearman’s correlation were performed to test for associations between these imaging parameters and the blood-based biomarkers NT-proBNP and CRP; logistic regression models were used to assess the performance of these biomarkers in predicting the radiological parameters. Results A total of 309 subjects were examined for this study. Subjects had a mean age of 65.6±11.1 years, 66.7% of them were males, and 62.4% were current smokers, with a mean FEV1 54.4%±21.5% of predicted. Blood NT-proBNP concentrations were associated with cardiac enlargement (area under the curve [AUC] =0.72, P<0.001), pulmonary edema (AUC =0.63, P=0.009), and pleural effusion on CXR (AUC =0.64, P=0.01); whereas on CT images, NT-proBNP concentrations were associated with pleural effusion (AUC =0.71, P=0.002). Serum CRP concentrations, on the other hand, were associated with consolidation on CT images (AUC =0.75, P<0.001), ground glass opacities (AUC =0.64, P=0.028), and pleural effusion (AUC =0.72, P<0.001) on CT images. A serum CRP sensitivity-oriented cutoff point of 11.5 mg/L was selected for the presence of consolidation on CT images in subjects admitted as cases of AECOPD, which has a sensitivity of 91% and a specificity of 53% (P<0.001). Conclusion Elevated CRP may indicate the presence of pneumonia, while elevated NT-proBNP may indicate cardiac dysfunction. These readily available blood-based biomarkers may provide more accurate phenotyping of AECOPD and enable the discovery of more precise therapies.
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Zheng YZ, DeMarco ML. Manipulating trypsin digestion conditions to accelerate proteolysis and simplify digestion workflows in development of protein mass spectrometric assays for the clinical laboratory. CLINICAL MASS SPECTROMETRY 2017. [DOI: 10.1016/j.clinms.2017.10.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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