The study was performed at the V.A. Nasonova Research Institute of Rheumatology within the framework of the fundamental topic FURS-2022–003

Background Systemic lupus erythematosus (SLE) is a multi-system autoimmune disease, characterized by hyperactive T and B cells, autoantibody production, immune complex deposition and multi-organ damage. The antiphospholipid syndrome (APS), initially described in SLE, occurs in 20–35% of patients with this condition and conveys a worse prognosis.

Purpose To evaluate the effect of antiphospholipid antibodies (aPL) on the activity and the damage index (DI) of SLE.

Methods The study included 112 patients with SLE (94 women and 18 men), of which 50 (45%) patients with SLE and APS and 62 (55%) patients with SLE. Mean age was 36.0 [26.5–44.5], disease duration was 7.6 [2.7–17.5]. All patients were determined by C3 and C4 complement components, IgG-, IgM-anti-cardiolipin (aCL), IgG-, IgM-anti-β2-glycoprotein (aß2GP1), IgG-, IgM-antibodies to the phosphatidylserine/prothrombin complex (aPS/PT) by enzyme immunoassay (ELISA) and IgG-, IgM-, IgA-aCL-, IgG-, IgM-, IgA-aß2GP1, IgG-aß2HP1-Domen1 (aß2HP1-D1) by chemiluminescence analysis (CLA). The activity of SLE was assessed on a scale SLE Disease Activity Index-2000 (SLEDAI-2K). The Systemic Lupus International Collaborating Clinics/American College of Rheumatology (SLICC/ACR) DI was developed to assess an ongoing reflection of disease activity in SLE patients and to measure irreversible damage resulting from SLE disease activity and its treatment.

Results Patients were divided into 5 groups depending on the activity of SLE: no activity (SLEDAI =0) – 12 patients (11%), low activity (SLEDAI 1–5) – 48 patients (43%), moderate activity (SLEDAI 6–10) – 24 patients (21%), high activity (SLEDAI 11–19) – 18 patients (16%), very high activity (SLEDAI >20) – 10 patients (9%).

All patients were divided into 4 groups depending on the severity of damage: no damage (0) – 61 patients (54%), low DI (1) – 19 patients (17%), moderate DI (2–4) – 28 patients (25%), high DI (>4) – 4 patients (4%). Mean SLICC/ACR DI in patients with SLE and APS was 1,66±1,8 and in patients with SLE was 0,72±1,39.

Based on the average values of the control group for the determination of IgA aCL, IgA aß2-GP1 and IgG/IgM aFs/Pt, the levels of positivity were allocated according to the formulas (including manufacturer’s values): arithmetic mean (M) + 3 or 5 standard deviations (SD): M+3SD and M+5SD. The obtained norms are: aß2HP1-D1>19 chemiluminescent units (CU), IgA aCL>18,9 CU, IgA aß2-GP1>20,0 CU, IgG aPS/PT>73,0U/ml, IgM aPS/PT>18,0U/ml.

The SLE activity depending on antiphospholipid antibodies and hypocomplementemia is presented in Table 1.

Conclusions In patients with SLE, SLEDAI-2k is significantly higher than in patients with SLE and APS (p=0,01). In patients with SLE and APS, SLICC/ACR DI and moderate DI were significantly higher than in patients with SLE (p=0,002 and p=0,02 respectively). Hypocomplementemia C3 and C4 and positivity by IgG-aCL, IgG-aß2GP1 by ELISA, IgG-aß2HP1-D1, IgG aPS/PT, IgM aPS/PT were significantly associated with SLE activity according to SLEDAI-2K.