Cohort description
Seventy one clinically diagnosed SLE patients, according to the American College of Rheumatology (ACR) criteria with biopsy-proven LN, all from Nephrology Clinics of University Hospital “Tzaritza Ioanna – ISUL”, Medical University of Sofia were included in the study.
LN activity was defined according to the British Islet Lupus Assessment Group (BILAG) renal score [23, 24]. All patients were divided into four BILAG categories as follows: 23 patients (31.08%) with category A LN, 24 patients (32.43%) with category B LN, 8 patients (10.81%) with category C LN and 19 patients (25.68%) with category D LN. There were no patients with category E LN in our cohort.
The patients with biopsy-proven LN were also distributed according to the LN classification of the International Society of Nephrology (ISN) and the Renal Pathology Society (RPS) [25, 26] as follows: 4 patients (5.63%) had LN Class I, 23 patients (32.39%) had LN Class II, 7 patients (9.86%) had LN Class III, 25 patients (35.21%) had LN Class IV, 11 patients (15.49%) had LN Class V, 1 patient (1.41%) had LN Class VI.
The presences of antinuclear antibodies (ANA) were detected by indirect immunofluorescence and levels of anti-dsDNA antibodies were tested by ELISA (U/mL) in University Hospital “Tzaritza Ioanna – ISUL”– Sofia. Pathologically elevated ANA titers (over 1:80) were found in 50 (69.4%) of patients and pathologically elevated levels of anti-dsDNA were found in 31 (40.8%) of patients.
The C4 and C3 complement components in plasma were measured by immunodiffusion. Reference ranges for C3 were from 0.75 to 1.65 g/L, and for C4 – 0.20 to 0.65 g/L. C3 hypocompletemia was detected in 14 (19.7%, 14/66). C4 hypocompletemia was detected in 28 (39.4%, 28/71). Both C3 and C4 hypocompletemia were detected in 13 (19.8%).
Seventy two healthy volunteers, age and gender matched to the patients, were included as a control group. All healthy volunteers were without autoimmune and infectious inflammatory diseases, and without renal, hepatic and haematopoietic dysfunctions.
The study had the approval of the Ethics Review Board of Medical University of Varna (protocol №62/04.05.2017) and each patient and healthy volunteer signed a consent form of enrolment.