PT - JOURNAL ARTICLE AU - Trujillo Aguilera, Antonio AU - Bernardo Serrano, Raquel AU - Navas, Ana AU - Alcaide Molina, Juan AU - Alvarez Romero, Paula AU - Jurado Roger, Aurora TI - Longitudinal study of patients with discrepant results in CLIFT and a solid-phase dsDNA antibody assay: does a gold standard dsDNA assay exist? AID - 10.1136/lupus-2023-000984 DP - 2023 Oct 01 TA - Lupus Science & Medicine PG - e000984 VI - 10 IP - 2 4099 - http://lupus.bmj.com/content/10/2/e000984.short 4100 - http://lupus.bmj.com/content/10/2/e000984.full SO - Lupus Sci Med2023 Oct 01; 10 AB - Objective Antidouble-stranded DNA (dsDNA) antibodies are essential for diagnosis and follow-up of systemic lupus erythematous (SLE). To ensure the best diagnostic approach, most healthcare laboratories opt for a combination of highly sensitive methods, such as solid-phase immunoassays, and highly specific methods, such as the Crithidia luciliae indirect immunofluorescence test (CLIFT). Even so, discordant results are common, thus hindering the diagnostic process. Therefore, this study aimed to characterise a cohort of patients with discrepant results for a dsDNA fluorescence enzyme immunoassay (FEIA) and CLIFT during 2016–2018 and to follow patients up until December 2021.Methods We performed an observational, longitudinal and retrospective study on 417 samples from 257 patients who had been referred for suspected connective tissue diseases or followed up after diagnosis. All of them were positive for antinuclear antibodies (ANAs) using an indirect immunofluorescence assay (IFA) on Hep-2 cells, the entry criterion in our laboratory, and positive for FEIA dsDNA. Samples were then tested with CLIFT according to our routine protocol, which includes CLIFT testing after FEIA dsDNA results ≥10 UI/ml. After the assessment of data quality, the final analysis was based on 222 patients.Results Eighty-three patients (37.4%) had positive results in both tests and met the diagnostic criteria for SLE. However, 139 patients (62.6%) had discrepant results (FEIA+, CLIFT–). Of these, 58 patients (41.7%) had a diagnosis of SLE, with 47 (33.8%) having been previously diagnosed and under treatment. The remaining 11 patients (7.9%) had a new diagnosis of SLE, which was made up within 4 years of the initial screening. A total of 81 of the 139 patients (57.5%) with discrepant results did not meet lupus criteria during the follow-up period.Conclusions The study showed that CLIFT could be negative in both treated and newly diagnosed SLE, thus underlining the importance of follow-up of dsDNA-positive results using solid-phase tests. Therefore, quantitative tests such as FEIA could add value to the diagnosis and management of patients with suspected SLE.Data are available upon reasonable request. All data collected, including fully anonymised participant data, are available. This information includes fully anonymised participant data and a data dictionary. Related documents (study protocol, statistical analysis and ethics committee approval) are available from the date of publication onward at the email address aurora.jurado.sspa@juntadeandalucia.es. Data will be shared after approval of proposals by the Ethics Committee of University Hospital Reina Sofía.