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.