Establishment of ELISA-comparable moderate and high thresholds for anticardiolipin and anti-β2 glycoprotein I chemiluminescent immunoassays according to the 2023 ACR/EULAR APS classification criteria and evaluation of their diagnostic performance

Žigon, Polona (author), Boštic, Nika (author), Ambrožič, Aleš (author), Rotar, Žiga (author), Blokar, Elizabeta (author), Ogrič, Manca (author), Čučnik, Saša (author)

Objectives: Recently published 2023 ACR/EULAR APS classification criteria emphasize the importance of quantifying single-, double-, and triple-antiphospholipid antibody positivity, distinguishing between IgG and IgM isotypes, and delineating moderate/high levels of anticardiolipin (aCL) and anti-β2 glycoprotein I (anti-β2GPI) antibodies. We aimed to establish clinically important moderate/high thresholds for aCL and anti-β2GPI IgG/IgM chemiluminescent immunoassays (CLIA), in particular QUANTA Flash, comparable to our in-house ELISAs used for over two decades, and to evaluate their diagnostic performance. Methods: QUANTA Flash CLIA and in-house ELISAs were used to measure aCL and anti-β2GPI IgG/IgM. Moderate thresholds for QUANTA Flash CLIA were determined using a non-parametric approach, calculating a 99th percentile on serum samples from 139 blood donors, and by mirroring the diagnostic performance of in-house ELISA on 159 patient samples. Results: Thresholds for QUANTA Flash CLIA achieving diagnostic performance equivalent to in-house ELISAs were 40 CU for moderate and 80 CU for high levels for aCL and anti-β2GPI IgG and IgM. The assays showed good qualitative agreement, ranging from 76.10 to 91.19 %. When considering in-house ELISA results, 14 out of 80 (17.5 %) patients did not fulfill the new ACR/EULAR laboratory classification criteria, while 27 out of 80 (33.8 %) did not when considering QUANTA Flash CLIA results. Conclusions: We determined moderate and high thresholds for aCL and anti-β2GPI IgG and IgM detected with QUANTA Flash CLIA, aligning with long-established in-house ELISA thresholds. These thresholds are crucial for seamlessly integrating of the new 2023 ACR/EULAR classification criteria into future observational clinical studies and trials.

• Language: English
• Keywords: anti-β2GPI, anticardiolipin, antiphospholipid syndrome, classification criteria
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FFA - Faculty of Pharmacy; MF - Faculty of Medicine
• Publication status: Published
• Publication version: Version of Record
• Year: 2025
• Number of pages: Str. 164–176
• Numbering: Vol. 63, iss. 1
• PID: 20.500.12556/RUL-165282
• UDC: 616-097
• ISSN on article: 1437-4331
• DOI: 10.1515/cclm-2024-0570
• COBISS.SI-ID: 203693059
• Publication date in RUL: 29.11.2024

Record is a part of a journal

• Title: Clinical chemistry and laboratory medicine
• Shortened title: Clin. chem. lab. med.
• Publisher: De Gruyter
• ISSN: 1437-4331
• COBISS.SI-ID: 680355

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: anti-β2GPI, antikardiolipin, antifosfolipidni sindrom, merila za razvrščanje

Projects

• Funder: ARIS - Slovenian Research and Innovation Agency
• Project number: P3-0314
• Name: Sistemske avtoimunske bolezni