Phenotypic subgroup in serologically active clinically quiescent systemic lupus erythematosus: A cluster analysis based on CSTAR cohort.

Background: Serologically active clinically quiescent (SACQ) is a state within systemic lupus erythematosus (SLE) characterized by elevated serologic markers without clinical activity. The heterogeneity in SACQ patients poses challenges in disease management. This multicenter prospective study aimed to identify distinct SACQ subgroups and assess their utility in predicting organ damage.

Methods: SACQ was defined as a sustained period of at least 6 months with persistent serologic activity, marked by positive anti-double-stranded DNA (dsDNA) antibodies and/or hypocomplementemia, and without clinical activity. Cluster analysis was employed, utilizing 16 independent components to delineate phenotypes.

Findings: Among the 4,107 patients with SLE, 990 (24.1%) achieved SACQ within 2.0 ± 2.3 years on average. Over a total follow-up of 7,105.1 patient years, 340 (34.3%) experienced flares, and 134 (13.5%) developed organ damage. Three distinct SACQ subgroups were identified. Cluster 1 (n = 219, 22.1%) consisted predominantly of elderly males with a history of major organ involvement at SLE diagnosis, showing the highest risk of severe flares (16.4%) and organ damage (27.9%). Cluster 2 (n = 279, 28.2%) was characterized by milder disease and a lower risk of damage accrual (5.7%). Notably, 86 patients (30.8%) in cluster 2 successfully discontinued low-dose glucocorticoids, with 49 of them doing so without experiencing flares. Cluster 3 (n = 492, 49.7%) featured the highest proportion of lupus nephritis and a moderate risk of organ damage (11.8%), with male patients showing significantly higher risk of damage (hazard ratio [HR] = 4.51, 95% confidence interval [CI], 1.82-11.79).

Conclusion: This study identified three distinct SACQ clusters, each with specific prognostic implications. This classification could enhance personalized management for SACQ patients.

Funding: This work was funded by the National Key R&D Program (2021YFC2501300), the Beijing Municipal Science & Technology Commission (Z201100005520023), the CAMS Innovation Fund (2021-I2M-1-005), and National High-Level Hospital Clinical Research Funding (2022-PUMCH-D-009).