Longitudinal Study Reveals Which UCTD Patients Are Most Likely to Evolve to Lupus Under Updated 2019 Classification Criteria
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A longitudinal study from the Lupus Clinic at Sapienza University of Rome followed 201 patients with undifferentiated connective tissue disease (UCTD) and found that more patients than previously recognized already meet current lupus classification criteria when the updated 2019 EULAR/ACR standards are applied. At first visit, 13.4% already qualified for a systemic lupus erythematosus (SLE) diagnosis under the new criteria, and an additional 7.8% evolved into SLE during an average follow-up of nearly four years. The findings help clarify which serological and clinical features at diagnosis signal the greatest risk for disease evolution, giving patients and rheumatologists a clearer roadmap for monitoring and earlier intervention.
Abstract
Undifferentiated connective tissue disease (UCTD) is diagnosed when patients show signs and symptoms of a systemic autoimmune disease, including a positive antinuclear antibody (ANA), but do not yet fulfill the full classification criteria for a specific connective tissue disease such as systemic lupus erythematosus (SLE), rheumatoid arthritis, or systemic sclerosis. Because UCTD is a heterogeneous condition, predicting which patients will remain undifferentiated and which will evolve into a defined disease has been a major clinical challenge. The 2019 EULAR/ACR classification criteria for SLE introduced a weighted scoring system that replaced the older 1997 ACR criteria, potentially reclassifying some UCTD patients as having SLE at first evaluation.
This longitudinal, observational, retrospective study enrolled 201 UCTD patients followed at the Lupus Clinic of Sapienza University of Rome since 2008 (F/M 191/10, median age 46 years), with clinical evaluations every six months. Patients were assessed for new clinical and laboratory features suggesting specific autoimmune diseases. The 2019 EULAR/ACR SLE classification criteria were retrospectively applied at both the first and last clinical visit to quantify the impact of the updated criteria. Logistic regression was used to identify baseline factors associated with SLE reclassification.
At the first visit, 27 patients (13.4%) already met the 2019 EULAR/ACR SLE classification criteria despite having been diagnosed with UCTD under older standards. During a mean observation period of 45.9 months, an additional 11 patients (7.8%) could be reclassified as having SLE at their last visit. Logistic regression identified thrombocytopenia, anti-dsDNA or anti-Sm antibody positivity, and low complement C4 levels as the strongest factors associated with meeting SLE classification criteria. Joint involvement was also significantly associated. The authors conclude that the 2019 EULAR/ACR criteria substantially affect how UCTD cohorts are classified, and that identifying these serological markers at baseline provides clinically meaningful prognostic information.