1
|
Musso G, Zoccarato M, Gallo N, Plebani M, Basso D. Hook-effect in MAGLUMI immunoassay for serum anti-GAD antibodies in neurological disorders: When "wrong" matrix is the right choice. Clin Chim Acta 2024; 558:119679. [PMID: 38642630 DOI: 10.1016/j.cca.2024.119679] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2024] [Revised: 03/26/2024] [Accepted: 04/17/2024] [Indexed: 04/22/2024]
Abstract
Antibodies against glutamic acid decarboxylase (anti-GAD) are a valuable diagnostic tool to detect severe autoimmune conditions as type 1 diabetes mellitus (T1DM) and anti-GAD related neurological disorders, having the latter more often anti-GAD concentrations in serum multiple times higher than in the former. Automated immunoassays, either with ELISA or chemiluminescent technology, are validated for diagnostic use in serum with analytical ranges suitable for T1DM diagnosis. In a patient presenting with a suspected autoimmune ataxia, anti-GAD testing on an automated chemiluminescent immunoassay (CLIA) resulted in slightly abnormal concentrations in serum (39.2 KIU/L) and very high concentrations in CSF (>280 KIU/L), thus prompting to proceed to serum dilutions to exclude a false negative result and a misdiagnosis. Different dilutions of serum resulted in nonlinear concentrations with endpoint result of 276,500 KIU/L at dilution 1:1000. CSF dilution was instead linear with endpoint result of 4050 KIU/L. In this case report we found that anti-GAD testing in CSF was essential to establish the clinical diagnosis and to suspect hook-effect in serum due to the excess of autoantibodies in this severe autoimmune condition.
Collapse
Affiliation(s)
- G Musso
- Department of Medicine-DIMED, University of Padova, Padova, Italy; Laboratory Medicine Unit, University-Hospital of Padova, Padova, Italy.
| | - M Zoccarato
- Neurology Unit, Ospedale Sant'Antonio, University-Hospital of Padova, Padova, Italy
| | - N Gallo
- Laboratory Medicine Unit, University-Hospital of Padova, Padova, Italy
| | - M Plebani
- Department of Medicine-DIMED, University of Padova, Padova, Italy; Laboratory Medicine Unit, University-Hospital of Padova, Padova, Italy
| | - D Basso
- Department of Medicine-DIMED, University of Padova, Padova, Italy; Laboratory Medicine Unit, University-Hospital of Padova, Padova, Italy
| |
Collapse
|
2
|
Gastaldi M, Mariotto S, Giannoccaro MP, Iorio R, Zoccarato M, Nosadini M, Benedetti L, Casagrande S, Di Filippo M, Valeriani M, Ricci S, Bova S, Arbasino C, Mauri M, Versino M, Vigevano F, Papetti L, Romoli M, Lapucci C, Massa F, Sartori S, Zuliani L, Barilaro A, De Gaspari P, Spagni G, Evoli A, Liguori R, Ferrari S, Marchioni E, Giometto B, Massacesi L, Franciotta D. Subgroup comparison according to clinical phenotype and serostatus in autoimmune encephalitis: a multicenter retrospective study. Eur J Neurol 2020; 27:633-643. [PMID: 31814224 DOI: 10.1111/ene.14139] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Accepted: 12/03/2019] [Indexed: 12/21/2022]
Abstract
BACKGROUND AND PURPOSE Autoimmune encephalitides (AE) include a spectrum of neurological disorders whose diagnosis revolves around the detection of neuronal antibodies (Abs). Consensus-based diagnostic criteria (AE-DC) allow clinic-serological subgrouping of AE, with unclear prognostic implications. The impact of AE-DC on patients' management was studied, focusing on the subgroup of Ab-negative-AE. METHODS This was a retrospective multicenter study on patients fulfilling AE-DC. All patients underwent Ab testing with commercial cell-based assays (CBAs) and, when available, in-house assays (immunohistochemistry, live/fixed CBAs, neuronal cultures) that contributed to defining final categories. Patients were classified as Ab-positive-AE [N-methyl-d-aspartate-receptor encephalitis (NMDAR-E), Ab-positive limbic encephalitis (LE), definite-AE] or Ab-negative-AE (Ab-negative-LE, probable-AE, possible-AE). RESULTS Commercial CBAs detected neuronal Abs in 70/118 (59.3%) patients. Testing 37/48 Ab-negative cases, in-house assays identified Abs in 11 patients (29.7%). A hundred and eighteen patients fulfilled the AE-DC, 81 (68.6%) with Ab-positive-AE (Ab-positive-LE, 40; NMDAR-E, 32; definite-AE, nine) and 37 (31.4%) with Ab-negative-AE (Ab-negative-LE, 17; probable/possible-AE, 20). Clinical phenotypes were similar in Ab-positive-LE versus Ab-negative-LE. Twenty-four/118 (20.3%) patients had tumors, and 19/118 (16.1%) relapsed, regardless of being Ab-positive or Ab-negative. Ab-positive-AE patients were treated earlier than Ab-negative-AE patients (P = 0.045), responded more frequently to treatments (92.3% vs. 65.6%, P < 0.001) and received second-line therapies more often (33.3% vs. 10.8%, P = 0.01). Delays in first-line therapy initiation were associated with poor response (P = 0.022; odds ratio 1.02; confidence interval 1.00-1.04). CONCLUSIONS In-house diagnostics improved Ab detection allowing better patient management but was available in a patient subgroup only, implying possible Ab-positive-AE underestimation. Notwithstanding this limitation, our findings suggest that Ab-negative-AE and Ab-positive-AE patients share similar oncological profiles, warranting appropriate tumor screening. Ab-negative-AE patients risk worse responses due to delayed and less aggressive treatments.
Collapse
Affiliation(s)
- M Gastaldi
- Neuroimmunology Laboratory, IRCCS Mondino Foundation, Pavia, Italy
| | - S Mariotto
- Neurology Unit, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - M P Giannoccaro
- Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy.,UOC Clinica Neurologica, IRCCS Istituto delle Scienze Neurologiche di Bologna, Bologna, Italy
| | - R Iorio
- Istituto di Neurologia, Fondazione Policlinico Universitario 'Agostino Gemelli' IRCCS, Rome, Italy.,Universita' Cattolica del Sacro Cuore, Rome, Italy
| | - M Zoccarato
- Ospedale S. Antonio, AULSS Euganea, Padua, Italy.,Neuroimmunology Group, Paediatric Research Institute "Città della Speranza", Padua, Italy
| | - M Nosadini
- Neuroimmunology Group, Paediatric Research Institute "Città della Speranza", Padua, Italy.,Paediatric Neurology and Neurophysiology Unit, Department of Women's and Children's Health, University Hospital of Padua, Padua, Italy
| | - L Benedetti
- IRCCS Ospedale Policlinico S. Martino, Genoa, Italy
| | - S Casagrande
- Neurosciences Department, Florence University, Italy.,Careggi University Hospital, Florence, Italy
| | - M Di Filippo
- Neurology Clinic, S. Maria della Misericordia Hospital, Perugia University, Perugia, Italy
| | - M Valeriani
- Neurology Unit, Bambino Gesù Children Hospital, Rome, Italy
| | - S Ricci
- Ospedale 'Città-di-Castello-e-Branca', Italy
| | - S Bova
- Pediatric Neurology Unit, ASST Fatebenefratelli Sacco, Children Hospital Vittore Buzzi, Milan, Italy
| | | | - M Mauri
- Neurology and Stroke Unit, Insubria University, Varese, Italy
| | - M Versino
- Neurology and Stroke Unit, Insubria University, Varese, Italy
| | - F Vigevano
- Neurology Unit, Bambino Gesù Children Hospital, Rome, Italy
| | - L Papetti
- Neurology Unit, Bambino Gesù Children Hospital, Rome, Italy
| | - M Romoli
- Neurology Clinic, S. Maria della Misericordia Hospital, Perugia University, Perugia, Italy.,Neurology Unit, Rimini "Infermi" Hospital - AUSL Romagna, Rimini, Italy
| | - C Lapucci
- IRCCS Ospedale Policlinico S. Martino, Genoa, Italy
| | - F Massa
- IRCCS Ospedale Policlinico S. Martino, Genoa, Italy
| | - S Sartori
- Neuroimmunology Group, Paediatric Research Institute "Città della Speranza", Padua, Italy.,Paediatric Neurology and Neurophysiology Unit, Department of Women's and Children's Health, University Hospital of Padua, Padua, Italy
| | - L Zuliani
- Neuroimmunology Group, Paediatric Research Institute "Città della Speranza", Padua, Italy.,Neurology Department, Ospedale S. Bortolo, Vicenza, Italy
| | - A Barilaro
- Careggi University Hospital, Florence, Italy
| | - P De Gaspari
- Neuroimmunology Group, Paediatric Research Institute "Città della Speranza", Padua, Italy
| | - G Spagni
- Universita' Cattolica del Sacro Cuore, Rome, Italy
| | - A Evoli
- Istituto di Neurologia, Fondazione Policlinico Universitario 'Agostino Gemelli' IRCCS, Rome, Italy.,Universita' Cattolica del Sacro Cuore, Rome, Italy
| | - R Liguori
- Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy.,UOC Clinica Neurologica, IRCCS Istituto delle Scienze Neurologiche di Bologna, Bologna, Italy
| | - S Ferrari
- Neurology Unit, Department of Neuroscience, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | - E Marchioni
- Neuroncology Unit, IRCCS Mondino Foundation, Pavia, Italy
| | | | - L Massacesi
- Neurosciences Department, Florence University, Italy.,Careggi University Hospital, Florence, Italy
| | - D Franciotta
- Neuroimmunology Laboratory, IRCCS Mondino Foundation, Pavia, Italy
| |
Collapse
|