key: cord-0276334-h5y8e2jr authors: Zorn-Pauly, L.; von Stuckrad, A. S. L.; Klotsche, J.; Rose, T.; Kallinich, T.; Enghard, P.; Ostendorf, L.; Burns, M.; Doerner, T.; Meisel, C.; Schneider, U.; Unterwalder, N.; Burmester, G.; Hiepe, F.; Alexander, T.; Biesen, R. title: Evaluation of SIGLEC1 in the diagnosis of suspected systemic lupus erythematosus date: 2021-09-27 journal: nan DOI: 10.1101/2021.09.25.21263771 sha: 9b778a3ea277ac476704f5c873805c2fc890e0fe doc_id: 276334 cord_uid: h5y8e2jr Objectives: To evaluate and compare the diagnostic accuracy utility of SIGLEC1, a surrogate marker of type I IFN, compared to with established biomarkers in an inception cohort of systemic lupus erythematosus (SLE). Methods: SIGLEC1 was analysed by flow cytometry in our central laboratory facility in 232 patients referred to our institution with suspected SLE between October 2015 and September 2020. Results: SLE was confirmed in 76 of 232 patients (32.8%) according to the 2019 EULAR/ACR classification criteria and their . SIGLEC1 values were significantly higher in patients with SLE compared to patients without SLE (p<0.0001). A sensitivity of 98.7 %, a specificity of 82.1 %, a negative predictive value (NPV) of 99.2 % and a positive predictive value (PPV) of 72.8 % were calculated for SIGLEC1. Adjusted to the highest reported prevalence of SLE, the NPV and PPV were > 99.9 % and 0.1 %, respectively. Using ROC analysis and DeLlong testing, the area under the curve (AUC) for SIGLEC1 (AUC=0.95) was significantly higher than for ANA (AUC=0.88, p=0.031), C3 (AUC=0.83, p=0.001) and C4 (AUC=0.83, p=0.002) but not for anti-dsDNA antibodies (AUC=0.90, p=0.163). Conclusion: IFN-I pathway activation is detectable in almost most all newly diagnosed SLE patients, where SIGLEC1 outcompetes the performance of other biomarkers to exclude SLE with high predictability in suspected cases. Thus, a negative test result for SIGLEC1 is powerful to exclude SLE in suspected cases. Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune disease with a complex aetiology, mostly affecting women of childbearing age. The highest prevalence worldwide was reported in a national survey in the USA, with 241 cases per 100000 inhabitants [1] . Type-I interferon (IFN-I) plays a pivotal role in the disease pathogenesis and the type I interferon receptor antagonist anifrolumab had recently been approved by the FDA for the treatment of SLE. Among the multitude of interferon-stimulated genes, we have previously identified SIGLEC1 (sialic acid-binding immunoglobulin-like lectin-1, CD169), an adhesion molecule restricted to cells of the monocyte lineage, as a surrogate marker for activation of the IFN-I pathway [2] . Subsequent studies indicated that SIGLEC1 on monocytes correlates with disease activity and reflects response to targeted treatment approaches in SLE [3] [4] [5] . Although commonly determined by several centres utilizing different techniques and surrogate markers, little is known about the IFN-I activity during onset of the disease. Therefore, we aimed to investigate the diagnostic utility of the IFN-I surrogate marker SIGLEC1 in patients with suspected SLE. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) preprint The copyright holder for this this version posted September 27, 2021. ; https://doi.org/10.1101/2021.09.25.21263771 doi: medRxiv preprint In this retrospective study, SIGLEC1 was investigated in patients who have been referred to the Charité -University Medicine Berlin for suspected SLE between October 2015 and September 2020. The study was approved by the local ethics committee (EA2/105/18) and written informed consent was obtained from all participants. Patients were stratified into two groups: A) SLE according to EULAR/ACR 2019 classification criteria [6] or B) SLE-mimicking conditions. The disease activity was determined by the Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K) [7] . Patients pre-treated with a prednisolone dosage exceeding 100 mg/day were excluded from the study as glucocorticoids can suppress the IFN signature in a dose-and time-dependent manner. Measurement of SIGLEC1 was described elsewhere and values with a cut-off above 2500 antigens per monocyte were regarded as positive [8] . Statistical analysis was performed by using GraphPad Prism 8.4.3. The Fisher's exact test was used for nominal data. Mann-Whitney-U test (non-parametric) or the unpaired T-test (parametric) were performed for continuously distributed variables. To investigate the SIGLEC1 values during follow-up in SLE patients the Friedmann and Dunn's multiple comparisons test was used. A p-value of < 0.05 was considered statistically significant. All statistical tests were performed two-sided. ROC analysis was performed for the parameters SIGLEC1, anti-nuclear antibodies (ANA), antidouble-stranded (ds)DNA antibodies, serum complement factors C3 and C4 to evaluate their diagnostic performance. Areas under the curves were compared using the DeLong test [9] . . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) preprint From 232 patients with suspected SLE referred to our institution, 76 (32.8%) patients were diagnosed with SLE according to the EULAR/ACR 2019 SLE classification criteria. Details of their demographics, organ manifestations and disease activity are provided in Table S1 , and diagnosis of the remaining 156 patients with SLEmimicking conditions are provided in Table S2 . SIGLEC1 values were significantly higher in patients with SLE compared to patients without SLE (median MFI 10831 vs. To compare the diagnostic utility of SIGLEC1 with established biomarkers, we next investigated the Likelihood ratios (LR), which are commonly used to calculate and compare the benefit of performing a diagnostic test. LR's are defined as the change in the probability of the presence or absence of a disease given a positive (LR+) or negative (LR-) test result, and may be further subdivided into four categories according to their diagnostic utility : "none", "weak", "strong" and "superior [10] . By applying these categories, we found that both, negative ANA and SIGLEC1 results were "superior" to exclude SLE, while the other biomarkers were not helpful (Table 1 ). Conversely, the utility of decreased C4 levels and positive anti-Sm antibodies was "superior" and those of positive anti-dsDNA antibodies and SIGLEC1 values was "strong" in confirming the suspected diagnosis of SLE, while ANA titre or decreased C3 levels were not useful. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. In addition, we compared not only the performance of the tests at a given cut-off, but also across all possible readings by performing ROC curve analyses ( Figure 2 ). Anti-Sm antibodies could not be considered because they were only measured qualitatively. Area under the curve of SIGLEC1 was highest with 0.95. Using the DeLong-Test to compare the AUC´s, we found that the AUC of SIGLEC1 was significantly higher than that of the ANA (AUC=0.88, p=0.031), C3 (AUC = 0.83, p=0.001) and C4 (AUC=0.83, p=0.002). Only the AUC of anti-dsDNA antibodies (AUC=0.90, p=0.163) did not differ significantly from that of SIGLEC1. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) preprint This study has certain limitations. First, the number of included patients in our inception cohort was limited and included a subset of patients who were pre-treated. Second, our data were collected retrospectively in a single centre and validation of our results in a multicentre study is needed. Finally, this study lacks inclusion of other biomarkers established for IFN-I pathway activation. In conclusion, our data indicate that IFN-I pathway activation is detectable in nearly all patients at onset of SLE, and identifies the interferon biomarker SIGLEC1 as a powerful diagnostic tool to exclude SLE in suspected cases. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) preprint Competing interests None declared. Ethics approval: The present study was approved by the ethics committee of the Charité -Universitätsmedizin Berlin under EA2/105/18. All patients gave written informed consent. Patients were not involved in the study planning. The data is available upon reasonable request from the corresponding author. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) preprint The copyright holder for this this version posted September 27, 2021. ; https://doi.org/10.1101/2021.09.25.21263771 doi: medRxiv preprint Tables: Table 1 Biomarker . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) preprint The copyright holder for this this version posted September 27, 2021. ; https://doi.org/10.1101/2021.09.25.21263771 doi: medRxiv preprint Prevalence of physician-diagnosed systemic lupus erythematosus in the United States: results from the third national health and nutrition examination survey Sialic acidbinding Ig-like lectin 1 expression in inflammatory and resident monocytes is a potential biomarker for monitoring disease activity and success of therapy in systemic lupus erythematosus IFNalpha and its response proteins, IP-10 and SIGLEC-1, are biomarkers of disease activity in systemic lupus erythematosus Are interferon-related biomarkers advantageous for monitoring disease activity in systemic lupus erythematosus? A longitudinal benchmark study Targeting CD38 with Daratumumab in Refractory Systemic Lupus Erythematosus European League Against Rheumatism/American College of Rheumatology classification criteria for systemic lupus erythematosus Systemic lupus erythematosus disease activity index SIGLEC1 (CD169) is a sensitive biomarker for the deterioration of the clinical course in childhood systemic lupus erythematosus Comparing the areas under two or more correlated receiver operating characteristic curves: a nonparametric approach Users' guides to the medical literature. III. How to use an article about a diagnostic test. B. What are the results and will they help me in caring for my patients? The Evidence-Based Medicine Working Group Identification of interferon-inducible genes as diagnostic biomarker for systemic lupus erythematosus Interferon-stimulated gene 15 expression in systemic lupus erythematosus : Diagnostic value and association with lymphocytopenia Role of thrombocytosis in diagnosis of giant cell arteritis and differentiation of