BackgroundDigital diagnostic decision support tools promise to accelerate diagnosis and increase health care efficiency in rheumatology. Rheumatic? is an online tool developed by specialists in rheumatology and general medicine together with patients and patient organizations. It calculates a risk score for several rheumatic diseases. In the current pilot study, we retrospectively test Rheumatic? for its ability to differentiate symptoms from immune-mediated diseases from other rheumatic and musculoskeletal complaints and disorders in patients visiting rheumatology clinics. MethodsThe performance of Rheumatic? was tested using data from 175 patients from three university rheumatology centers covering two different settings:A. Risk-RA phase setting. Here, we tested whether Rheumatic? could predict the development of arthritis in 50 individuals with musculoskeletal complaints and anti-citrullinated protein antibody positivity from the KI (Karolinska Institutet)B. Early arthritis setting. Here, we tested whether Rheumatic? could predict the development of an immune-mediated rheumatic disease in i) EUMC (Erlangen) n=52 patients and ii) LUMC (Leiden) n=73 patients.In each setting, we examined the discriminative power of the total score with the Wilcoxon rank test and the area-under-the-receiver-operating-characteristic curve (AUC-ROC). Next, we calculated the test characteristics for these patients at a rheumatology setting passing the first or second threshold for at least one of the rheumatic diseases.ResultsThe total test score clearly differentiated between: A) individuals developing arthritis or not, median 245 versus 163, P < 0.0001, AUC-ROC = 75.3B) patients with an immune-mediated arthritic disease or not, in EUMC median 191 versus 107, P < 0.0001, AUC-ROC = 79.0, and LUMC median 262 versus 212, P < 0.0001, AUC-ROC = 53.6.Threshold-1 (advising on seeking primary care doctor) was highly specific in two centers (0.72, 0.87 and 0.23, respectively) and far more sensitive (0.67, 0.61 and 0.67) in KI, EUMC respectively LUMC.Threshold-2 was very specific in all three centers but not very sensitive: specificity of 1.0, 0.96 and 0.91, sensitivity 0.05, 0.07, 0.14 in KI, EUMC respectively LUMC. ConclusionsRheumatic? is a web-based patient-centered multilingual diagnostic tool capable of differentiating immune-mediated rheumatic conditions from other musculoskeletal problems. The scoring system might be further optimized, for which we will perform a prospective study.