Background Many patients with a clinical diagnosis of Systemic lupus erythematosus (SLE) do not fulfill the ACR 1997 classification criteria (ACR'97). Consequently, patients included in SLE studies might not be representative of the real spectrum of the disease. The new SLICC 2012 classification criteria (SLICC'12) were proposed to improve the sensitivity of SLE classification. However, these criteria require external validation.
Objectives To compare the sensitivity for SLE diagnosis of the ACR'97 and SLICC'12 classification criteria sets in a real life, multicenter, international SLE population.
Methods We included in this cross-sectional observational study all patients with a clinical diagnosis of SLE followed at the participating Rheumatology centers and registered in the Portuguese and Spanish national registries (Reuma.pt and RELESSER, respectively). For each patient, we evaluated the fulfillment of the ACR'97 and SLICC'12 criteria. The sensitivity for SLE diagnosis of each classification set was calculated. We compared the proportion of cases fulfilling ACR'97 and SLICC'12 using the McNemar's test. To compare dichotomous variables in two independent populations, we applied a Chi-square or Fisher's exact test, as appropriate. The statistical significance level was p<0.05.
Results We included 2055 SLE patients (female = 91.4%; Caucasian =93.5%; age at disease onset = 33.1±14.4; age at SLE diagnosis = 35.3±14.7; age at SLE criteria scoring = 47.4±14.6) from 17 centers.
The sensitivity for SLE diagnosis was higher with the SLICC'12 (93.1%) compared with the ACR'97 (85.6%) (p<0.0001). At least one of the classification criteria sets was fulfilled by 94.7% of cases. From 295 patients not fulfilling the ACR'97, 63% could be classified as SLE with SLICC'12. In the group of patients with positive SLE classification using the ACR'97 criteria, 1.8% did not fulfill the SLICC'12.
The sensitivity for SLE diagnosis increased with longer disease duration, for both the ACR'97 and SLICC'12 (p<0.0001). In the group of patients with <5 years since disease onset, there was a larger improved sensitivity of SLICC'12 (89.3%) compared to ACR'97 (76.0%) (p<0.0001); this difference in sensitivity reduced with longer disease duration, and loses significance for the group with >20 years of disease.
Conclusions In real-life clinical setting, the SLICC'12 classification criteria present a higher sensitivity for SLE compared to ACR'97. The SLICC'12 might allow a SLE classification earlier in the disease course.
Disclosure of Interest : None declared