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Background/objectives: The European League Against Rheumatism (EULAR)/American College of Rheumatology (ACR) 2019 classification criteria for systemic lupus erythematosus system showed high specificity, while attaining also high sensitivity. We hereby analysed the performance of the individual criteria items and their contribution to the overall performance of the criteria., Methods: We combined the EULAR/ACR derivation and validation cohorts for a total of 1197 systemic lupus erythematosus (SLE) and n=1074 non-SLE patients with a variety of conditions mimicking SLE, such as other autoimmune diseases, and calculated the sensitivity and specificity for antinuclear antibodies (ANA) and the 23 specific criteria items. We also tested performance omitting the EULAR/ACR criteria attribution rule, which defines that items are only counted if not more likely explained by a cause other than SLE., Results: Positive ANA, the new entry criterion, was 99.5% sensitive, but only 19.4% specific, against a non-SLE population that included other inflammatory rheumatic, infectious, malignant and metabolic diseases. The specific criteria items were highly variable in sensitivity (from 0.42% for delirium and 1.84% for psychosis to 75.6% for antibodies to double-stranded DNA), but their specificity was uniformly high, with low C3 or C4 (83.0%) and leucopenia <4.000/mm³ (83.8%) at the lowest end. Unexplained fever was 95.3% specific in this cohort. Applying the attribution rule improved specificity, particularly for joint involvement., Conclusions: Changing the position of the highly sensitive, non-specific ANA to an entry criterion and the attribution rule resulted in a specificity of >80% for all items, explaining the higher overall specificity of the criteria set., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2021. No commercial re-use. See rights and permissions. Published by BMJ.)

Objective: To develop new classification criteria for systemic lupus erythematosus (SLE) jointly supported by the European League Against Rheumatism (EULAR) and the American College of Rheumatology (ACR)., Methods: This international initiative had four phases. 1) Evaluation of antinuclear antibody (ANA) as an entry criterion through systematic review and meta-regression of the literature and criteria generation through an international Delphi exercise, an early patient cohort, and a patient survey. 2) Criteria reduction by Delphi and nominal group technique exercises. 3) Criteria definition and weighting based on criterion performance and on results of a multi-criteria decision analysis. 4) Refinement of weights and threshold scores in a new derivation cohort of 1,001 subjects and validation compared with previous criteria in a new validation cohort of 1,270 subjects., Results: The 2019 EULAR/ACR classification criteria for SLE include positive ANA at least once as obligatory entry criterion; followed by additive weighted criteria grouped in 7 clinical (constitutional, hematologic, neuropsychiatric, mucocutaneous, serosal, musculoskeletal, renal) and 3 immunologic (antiphospholipid antibodies, complement proteins, SLE-specific antibodies) domains, and weighted from 2 to 10. Patients accumulating ≥10 points are classified. In the validation cohort, the new criteria had a sensitivity of 96.1% and specificity of 93.4%, compared with 82.8% sensitivity and 93.4% specificity of the ACR 1997 and 96.7% sensitivity and 83.7% specificity of the Systemic Lupus International Collaborating Clinics 2012 criteria., Conclusion: These new classification criteria were developed using rigorous methodology with multidisciplinary and international input, and have excellent sensitivity and specificity. Use of ANA entry criterion, hierarchically clustered, and weighted criteria reflects current thinking about SLE and provides an improved foundation for SLE research., (© 2019, American College of Rheumatology.)

We can hardly meet references in the literature to the various circumstances and factors that played an important role in scientific discoveries, although interesting conclusions could be driven from them. So, e.g., in the case of Landsteiner it is sure, that his idea, to investigate the reason of the mechanism and of the formation of a phenomenon, came from the phenomenon itself: namely, from the agglutination called forth by the fortuitous mixing of the cadavers' blood in the dissecting room. The present paper deals with certain circumstances that played a role in the discovery of the Rh-Factors, resulting not only scientific, but practical consequences as well. The data used here were collected primarily from the memoirs of professors Wiener, Levine, Dahr and from those of Speiser (Vienna). The authors were helped in their research also by their personal contact with professor Dahr (Cologne) established in the sixties. Landsteiner was compelled to emigrate from Austria mainly by the vivid anti-Semitism of the early 20s. Supposedly, without his emigration the Rh Factors would have been discovered much later. Working in the Rockefeller Institute (New York) Landsteiner was provided with everything that was needed for his research. He had organised a team and, helped by his colleagues, he succeeded to open a new field in immunserology. Unfortunately, before he could have completed his scientific project, he had died--already as a Nobel-Prize winner--in 1943. His project was resumed by his colleagues. The method of Rh-examination, exceeding the field of medicine, quickly won a greater significance, in anthropology, genetics and in biology. It is worth to mention, that Landsteiner, had already indicated shortly after his discovery the fields, on which the Rh-examinations later played a significant role.