Use of the 2019 EULAR/ACR criteria for systemic lupus erythematosus identified an additional 17% of lupus patients in a cohort of 133 women with undifferentiated connective tissue disease.

Several studies have applied the 2019 EULAR/ACR criteria for systemic lupus erythematosus (SLE) to different patient populations, wrote Massimo Radin, MD, of S. Giovanni Bosco Hospital, Turin, Italy, and colleagues.

“However, it is unknown if the new classifications criteria for SLE might impact on the categorization of patients previously diagnosed with undifferentiated connective tissue disease (UCTD),” they said in a brief report published in Arthritis Care & Research.

In addition, “being classified or not as having SLE may pose clinical and logistic consequences, as patients with a diagnosis of ‘SLE’ might be followed up according to a specific local protocol and have in-label access to certain medications (such as biologics) or may be eligible for the participation in clinical trials,” they wrote.

The investigators applied the 2019 EULAR/ACR criteria to a cohort of 133 women with UCTD but no other diagnosis. The average age of the women was 38 years; the average disease duration was 10 years. Patients who scored 10 points or more on positive clinical and immunological domains at the start of the study were classified as SLE under the 2019 EULAR/ACR criteria.

Overall, 22 patients (17%) met the classification criteria for SLE at the time of their first pregnancy.

Compared with the other patients in the cohort who were not classified as SLE, patients classified as SLE under the 2019 EULAR/ACR criteria had significantly higher frequency of mucocutaneous manifestations (5% vs. 23%), arthritis (17% vs. 59%), isolated urine abnormalities (1% vs. 18%), and highly specific antibodies (15% vs. 50%).

In addition, patients who met the 2019 EULAR/ACR SLE criteria were significantly more likely to meet the ACR 1997 and SLICC criteria after an average follow-up of 9 years compared with the rest of the cohort (18.2% vs. 1.8%). Patients who met the 2019 EULAR/ACR criteria also had significantly shorter disease duration than that of the other patients in the UCTD cohort (8.23 years vs. 10.7 years) and were significantly more likely to develop preeclampsia during pregnancy (18% vs. 0%).

The findings were limited by several factors including the retrospective design of the study and possible lack of generalizability to male patients, the researchers noted.

The results support the need for improved classification criteria for UCTD, as early identification of specific conditions can help guide treatment and reduce the risk of more severe symptoms and complications, the authors said.

“When discriminating between conditions with a marked overlap, such as SLE and UCTD, the proposal of new classification criteria should balance specificity and sensitivity,” the researchers wrote. “When developing new classification criteria, one approach is to select patients and the control groups as representative as possible of the settings (the medical practices) in which these criteria will be used.”

The study received no outside funding. The researchers had no financial conflicts to disclose.

SOURCE: Radin M et al. Arthritis Care Res. 2020 Jul 23. doi: 10.1002/ACR.24391.