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Maharjan AS, Wyness SP, Ray JA, Willcox TL, Seiter JD, Genzen JR. Detection and characterization of estradiol (E2) and unconjugated estriol (uE3) immunoassay interference due to anti-bovine alkaline phosphatase (ALP) antibodies. Pract Lab Med 2019; 17:e00131. [PMID: 31538105 PMCID: PMC6745434 DOI: 10.1016/j.plabm.2019.e00131] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Revised: 07/17/2019] [Accepted: 08/26/2019] [Indexed: 11/15/2022] Open
Abstract
Objectives Competitive immunoenyzmatic assays for estradiol (E2) and unconjugated estriol (uE3) on UniCel DxI 800 Access immunoassay systems (Beckman Coulter) utilize bovine alkaline phosphatase (ALP) for amplification. In these assays, rare 'IND' error flags indicate that a relative light unit (RLU) raw result is past the high or low end of the calibration curve but cannot be differentiated from an instrument error or analytical interference. The present studies were conducted to establish a protocol to identify analytical interference and to characterize its mechanism when present. Design and methods Matrix and recovery studies were conducted to establish a protocol for interference identification. Spiking experiments with inactivated calf intestinal ALP were performed to determine whether interference could be blocked. Commercial anti-ALP antibodies (Abs) were spiked into human serum to model assay interference. Three E2 immunoassays which do not include ALP as a reagent component (cobas e602, Roche; Centaur XP, Siemens; ARCHITECT i2000SR, Abbott) were tested for comparative purposes. Results 1:2 dilution of specimen into Access Sample Diluent A (Beckman) differentiated IND error flags due to true low results (e.g. less than the analytical measurement range; AMR) from those due to assay interference. Interferences were reduced by pre-incubation with inactivated ALP and could be replicated by spiking with commercial anti-ALP Abs. Conclusions Patient anti-bovine ALP Abs can cause interference on DxI 800 E2 and uE3 assays. This model can be used to investigate interference risk with other ALP-dependent assays.
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Key Words
- ALP, alkaline phosphatase
- AMR, analytical measurement range
- Alkaline phosphatase
- Analytical systems
- CLIA, Clinical Laboratory Improvement Amendments
- E2, estradiol
- Endocrinology
- IND, indeterminate ‘no value’ error flag
- Immunoassay
- Interference
- MoM, multiple of the median
- PBS, phosphate buffered saline
- RLU, relative light unit
- ddH2O, demineralized distilled water
- uE3, unconjugated estriol
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Affiliation(s)
- Anu S. Maharjan
- Department of Pathology, University of Utah, 500 Chipeta Way, Salt Lake City, UT, 84108, USA
| | - Sara P. Wyness
- ARUP Institute for Clinical and Experimental Pathology, 500 Chipeta Way, Salt Lake City, UT, 84108, USA
| | - Julie A. Ray
- ARUP Institute for Clinical and Experimental Pathology, 500 Chipeta Way, Salt Lake City, UT, 84108, USA
| | - Tanya L. Willcox
- ARUP Laboratories, 500 Chipeta Way, Salt Lake City, UT, 84108, USA
| | | | - Jonathan R. Genzen
- Department of Pathology, University of Utah, 500 Chipeta Way, Salt Lake City, UT, 84108, USA
- ARUP Institute for Clinical and Experimental Pathology, 500 Chipeta Way, Salt Lake City, UT, 84108, USA
- ARUP Laboratories, 500 Chipeta Way, Salt Lake City, UT, 84108, USA
- Corresponding author. University of Utah, Department of Pathology, ARUP Laboratories, 500 Chipeta Way, Mail Code 115, Salt Lake City, UT, 84108, USA.
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Vrolix K, Fraussen J, Molenaar PC, Losen M, Somers V, Stinissen P, De Baets MH, Martínez-Martínez P. The auto-antigen repertoire in myasthenia gravis. Autoimmunity 2010; 43:380-400. [PMID: 20380581 DOI: 10.3109/08916930903518073] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Myasthenia Gravis (MG) is an antibody-mediated autoimmune disorder affecting the postsynaptic membrane of the neuromuscular junction (NMJ). MG is characterized by an impaired signal transmission between the motor neuron and the skeletal muscle cell, caused by auto-antibodies directed against NMJ proteins. The auto-antibodies target the nicotinic acetylcholine receptor (nAChR) in about 90% of MG patients. In approximately 5% of MG patients, the muscle specific kinase (MuSK) is the auto-antigen. In the remaining 5% of MG patients, however, antibodies against the nAChR or MuSK are not detectable (idiopathic MG, iMG). Although only the anti-nAChR and anti-MuSK auto-antibodies have been demonstrated to be pathogenic, several other antibodies recognizing self-antigens can also be found in MG patients. Various auto-antibodies associated with thymic abnormalities have been reported, as well as many non-MG-specific auto-antibodies. However, their contribution to the cause, pathology and severity of the disease is still poorly understood. Here, we comprehensively review the reported auto-antibodies in MG patients and discuss their role in the pathology of this autoimmune disease.
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Affiliation(s)
- Kathleen Vrolix
- Division of Neuroscience, School of Mental Health and Neuroscience, Faculty of Health, Medicine and Life Sciences, Maastricht University, Maastricht, The Netherlands
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Shigemoto K, Kubo S, Mori S, Yamada S, Akiyoshi T, Miyazaki T. Muscle weakness and neuromuscular junctions in aging and disease. Geriatr Gerontol Int 2010; 10 Suppl 1:S137-47. [DOI: 10.1111/j.1447-0594.2010.00608.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Apiwattanakul M, Mckeon A, Pittock SJ, Kryzer TJ, Lennon VA. Eliminating false-positive results in serum tests for neuromuscular autoimmunity. Muscle Nerve 2010; 41:702-4. [DOI: 10.1002/mus.21653] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Oh SJ. Muscle-specific receptor tyrosine kinase antibody positive myasthenia gravis current status. J Clin Neurol 2009; 5:53-64. [PMID: 19587811 PMCID: PMC2706412 DOI: 10.3988/jcn.2009.5.2.53] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2009] [Revised: 05/22/2009] [Accepted: 05/22/2009] [Indexed: 12/04/2022] Open
Abstract
Muscle-specific tyrosine-kinase-antibody-positive myasthenia gravis (MuSK-MG) has emerged as a distinct entity since 2001. This disease has been reported worldwide, but with varying rates among patients with generalized acetylcholine-receptor-antibody-negative MG. MuSK-MG was detected in approximately 37% of generalized acetylcholine receptor antibody-negative MG. MuSK-MG patients were predominantly female with more prominent facial and bulbar involvement and more frequent crises. Disease onset tended to be earlier. Patients tended to have a relatively poor edrophonium response but showed prominent decrement in the repetitive nerve stimulation test in the facial muscles. Patients were more likely to display poor tolerance of, or a lack of improvement with, anticholinesterase agents. Somewhat better response was observed with steroids and plasma exchange. Most were managed successfully with aggressive immunomodulatory therapies, although a higher proportion of MuSK-MG patients had a refractory course when compared with other forms of generalized MG. I present here an up-to-date overview on MuSK-MG based on our experience at the University of Alabama at Birmingham and the existing literature.
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Affiliation(s)
- Shin Joong Oh
- Distinguished Professor of Neurology, The University of Alabama at Birmingham, The Veterans Affairs Medical Center, Birmingham, Alabama, USA
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6
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Apiwattanakul M, McKeon A, Fryer JP, Hinson SR, Pittock SJ, Lennon VA. AQP4-IgG immunoprecipitation assay optimization. Clin Chem 2009; 55:592-4. [PMID: 19246407 DOI: 10.1373/clinchem.2008.116848] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Shigemoto K, Kubo S, Jie C, Hato N, Abe Y, Ueda N, Kobayashi N, Kameda K, Mominoki K, Miyazawa A, Ishigami A, Matsuda S, Maruyama N. Myasthenia Gravis Experimentally Induced with Muscle-specific Kinase. Ann N Y Acad Sci 2008; 1132:93-8. [DOI: 10.1196/annals.1405.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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Konishi T, Ohta K, Shigemoto K, Ohta M. Anti-alkaline phosphatase antibody positive myasthenia gravis. J Neurol Sci 2007; 263:89-93. [PMID: 17628604 DOI: 10.1016/j.jns.2007.06.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2007] [Revised: 04/19/2007] [Accepted: 06/08/2007] [Indexed: 11/26/2022]
Abstract
Anti-alkaline phosphatase antibody (AP Ab) was specific in 9% of 249 anti-acetylcholine receptor (AChR) Ab-positive myasthenia gravis (MG) (SPMG) patients but not in patients with AChR Ab-negative MG (SNMG), other neurological and immunological diseases, or healthy volunteers. No cross-reactivity and no significant titer correlation were found between AP Ab and AChR Ab. We confirmed immunologically by radioimmunoassay and western blot analysis the presence of antibodies directed against AP. AP Ab-positive SPMG patients were characterized clinically as having female predominance and a more severe form of generalized MG than AP Ab-negative SPMG patients, and about half required artificial ventilation at maximum severity. AP Ab's pathogenic role in MG is yet unclarified, but our findings show AP to be a novel antigen among the various autoantigens present in MG patients and in whom AP Ab may modify clinical symptoms.
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Affiliation(s)
- Tetsuro Konishi
- Department of Neurology, National Hospital Organization Utano National Hospital, 8, Ondoyama-cho, Narutaki, Ukyo-ku, Kyoto 616-8255, Japan.
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Ohta K, Shigemoto K, Fujinami A, Maruyama N, Konishi T, Ohta M. Clinical and experimental features of MuSK antibody positive MG in Japan. Eur J Neurol 2007; 14:1029-34. [PMID: 17718696 DOI: 10.1111/j.1468-1331.2007.01870.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We investigated the presence of antibodies (Abs) against muscle-specific tyrosine kinase (MuSK) in Japanese myasthenia gravis (MG) patients. MuSK Abs were found in 23 (27%) of 85 generalized seronegative MG (SNMG) patients but not in any of the ocular MG patients. MuSK Ab-positive patients were characterized as having female dominance (M:F, 5:18), age range at onset 18 to 72 (median 45) years old, and prominent oculobulbar symptoms (100%) with neck (57%) or respiratory (35%) muscle weakness. Limb muscle weakness was comparatively less severe (52%), thymoma absent. Most patients had good responses to simple plasma exchange and steroid therapy. MuSK IgG from all 18 patients was exclusively the IgG 4 subclass and bound mainly with the MuSK Ig 1-2 domain. Serial studies of 12 individuals showed a close correlation between the variation in MuSK Ab titers and MG clinical severity (P = 0.01 by Kruskal-Wallis). MuSK Ab titers were sharply decreased in patients who had a good response to early steroid therapy or simple plasma exchange, but there was no change, or a rapid increase on exacerbation after thymectomy. Measurement of MuSK Ab titers aids in the diagnosis of MG and the monitoring of clinical courses after treatment.
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Affiliation(s)
- K Ohta
- Clinical Research Center, Utano National Hospital, Kyoto, Japan.
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Leite MI, Jones M, Ströbel P, Marx A, Gold R, Niks E, Verschuuren JJGM, Berrih-Aknin S, Scaravilli F, Canelhas A, Morgan BP, Vincent A, Willcox N. Myasthenia gravis thymus: complement vulnerability of epithelial and myoid cells, complement attack on them, and correlations with autoantibody status. THE AMERICAN JOURNAL OF PATHOLOGY 2007; 171:893-905. [PMID: 17675582 PMCID: PMC1959483 DOI: 10.2353/ajpath.2007.070240] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In early-onset myasthenia gravis, the thymus contains lymph node-type infiltrates with frequent acetylcholine receptor (AChR)-specific germinal centers. Our recent evidence/two-step hypothesis implicates hyperplastic medullary thymic epithelial cells (expressing isolated AChR subunits) in provoking infiltration and thymic myoid cells (with intact AChR) in germinal center formation. To test this, we screened for complement attack in a wide range of typical generalized myasthenia patients. Regardless of the exact serology, thymi with sizeable infiltrates unexpectedly showed patchy up-regulation of both C5a receptor and terminal complement regulator CD59 on hyperplastic epithelial cells. These latter also showed deposits of activated C3b complement component, which appeared even heavier on infiltrating B cells, macrophages, and especially follicular dendritic cells. Myoid cells appeared particularly vulnerable to complement; few expressed the early complement regulators CD55, CD46, or CR1, and none were detectably CD59(+). Indeed, when exposed to infiltrates, and especially to germinal centers, myoid cells frequently labeled for C1q, C3b (25 to 48%), or even the terminal C9, with some showing obvious damage. This early/persistent complement attack on both epithelial and myoid cells strongly supports our hypothesis, especially implicating exposed myoid cells in germinal center formation/autoantibody diversification. Remarkably, the similar changes place many apparent AChR-seronegative patients in the same spectrum as the AChR-seropositive patients.
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Affiliation(s)
- Maria I Leite
- Department of Clinical Neurology, University of Oxford, Oxford, United Kingdom
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Rostedt Punga A, Ahlqvist K, Bartoccioni E, Scuderi F, Marino M, Suomalainen A, Kalimo H, Stålberg EV. Neurophysiological and mitochondrial abnormalities in MuSK antibody seropositive myasthenia gravis compared to other immunological subtypes. Clin Neurophysiol 2006; 117:1434-43. [PMID: 16737845 DOI: 10.1016/j.clinph.2006.03.028] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2005] [Revised: 03/21/2006] [Accepted: 03/30/2006] [Indexed: 11/19/2022]
Abstract
OBJECTIVE To compare the electrophysiological and histopathological features of immunological myasthenia gravis (MG) subtypes. METHODS Fifty MG patients underwent clinical examination, MuSK-Ab and AChR-Ab analysis. The majority underwent quantitative and single-fiber electromyography (QEMG, SFEMG), repetitive nerve stimulation and deltoid muscle biopsy. From muscle specimens with histological mitochondrial dysfunction, we amplified mitochondrial DNA (mtDNA). In specimens with mtDNA deletions, the nuclear gene POLG1 was sequenced. RESULTS Five AChR-Ab seropositive [AChR(+)] and 5 seronegative [AChR(-)] patients were MuSK-Ab seropositive [MuSK(+)]. Five of 7 neurophysiologically examined MuSK(+) patients (71%) had proximal myopathic pattern, compared to 7 of 31 MuSK(-)/AChR(+) patients (23%) (P=0.012). SFEMG was abnormal in all examined MuSK(+) patients. All 7 biopsied MuSK(+) and 32 MuSK(-) patients (89%) had cytochrome c oxidase (COX) negative fibers. Three of five MuSK(+) and 13 of 20 MuSK(-) patients analyzed had multiple mtDNA deletions but no POLG1 mutations. CONCLUSIONS Similar degree of SFEMG abnormalities was present in proximal muscles among MuSK(+) and AChR(+) patients. Proximal myopathy was over-represented in MuSK(+) patients; however, both MuSK(+) and MuSK(-) patients had mild myopathy with frequent mitochondrial abnormalities. SIGNIFICANCE The weakness in MuSK(+) patients is most likely due to disturbed neuromuscular transmission. The frequently encountered mitochondrial dysfunction in MG warrants further study.
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Affiliation(s)
- A Rostedt Punga
- Department of Clinical Neurophysiology, University Hospital, S-75185 Uppsala, Sweden.
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Shigemoto K, Kubo S, Maruyama N, Hato N, Yamada H, Jie C, Kobayashi N, Mominoki K, Abe Y, Ueda N, Matsuda S. Induction of myasthenia by immunization against muscle-specific kinase. J Clin Invest 2006; 116:1016-24. [PMID: 16557298 PMCID: PMC1409737 DOI: 10.1172/jci21545] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2004] [Accepted: 02/07/2006] [Indexed: 11/17/2022] Open
Abstract
Muscle-specific kinase (MuSK) is critical for the synaptic clustering of nicotinic acetylcholine receptors (AChRs) and plays multiple roles in the organization and maintenance of neuromuscular junctions (NMJs). MuSK is activated by agrin, which is released from motoneurons, and induces AChR clustering at the postsynaptic membrane. Although autoantibodies against the ectodomain of MuSK have been found in a proportion of patients with generalized myasthenia gravis (MG), it is unclear whether MuSK autoantibodies are the causative agent of generalized MG. In the present study, rabbits immunized with MuSK ectodomain protein manifested MG-like muscle weakness with a reduction of AChR clustering at the NMJs. The autoantibodies activated MuSK and blocked AChR clustering induced by agrin or by mediators that do not activate MuSK. Thus MuSK autoantibodies rigorously inhibit AChR clustering mediated by multiple pathways, an outcome that broadens our general comprehension of the pathogenesis of MG.
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Affiliation(s)
- Kazuhiro Shigemoto
- Department of Preventive Medicine, Ehime University School of Medicine, Ehime, Japan.
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