[Laboratory and morphologic parameters in patients with lupus nephritis]

Lupus nephritis is an example of glomerulonephritis mediated by immune complexes. The information obtained by kidney biopsy corroborates diagnosis and evaluation of disease activity, specify of prognosis and mode of treatment. The object of our study was to determine the prevalence of particular pathohistological types of lupus nephritis in our group of patients, to establish if there was a correlation of laboratory and morphological parameters, and to present the use of specific therapeutical protocols.

The study included 58 patients with diagnosed systemic lupus erythematosus (SLE) and lupus nephritis, who had biopsy of kidneys. The indications for biopsy were the following: proteinuria level over 0.5 g/24 hrs, erythrocyturia and cylindruria. The patients were examined and treated at the Institute of Allergology and Immunology, Clinical Centre in Belgrade, over the period 1994-2001. Within the testing, besides standard laboratory tests, the immunological evaluation was also performed as follows: the level of standard serum immunoglobulins, C3 and C4 components of complement, antinuclear antibodies (ANA) and antibodies to double-stranded DNA (dsDNA), were determined.

There was 84.48% of female patients in the studied group. The mean-age was 36.5 years, while the average duration of disease (SLE) to kidney biopsy was 28.3 months. Considering cytopenia, leukopenia was found in 26.79% of patients, lymphopenia was recorded in 62.26% of cases while anaemia was noted in 52.63% of patients. The values of serum creatinine were elevated in 25.86% of patients, while creatinine clearance rate was lower (below 80 ml/min) in 75% of cases. The values of proteinuria are illustrated in Graph I. Cylindruria was found in 20.69% of subjects, massive erythrocyturia in 44.83%, and 46.55% of patients had more than 5 red blood cells in urinary sediment. Regarding the pathohistological findings, according to WHO classification, the biopsy of kidneys revealed the following distribution: class I--3.45% of patients, class IIA--24.14%, class IIB--31.03%, class III--12.07%, class IV--24.14%, class V--3.35%, and class VI 1.72% of cases.

Within the immunological evaluation, the increased serum immunoglobulin G (IgG) level was found in 26.79% of subjects, suggesting that the consumption of complements in formation of immune complexes was the basic pathogenetic mechanism of lupus nephritis. Positive finding of ANA was recorded in about 95% of subjects, what was typical for SLE, while antibodies to dsDNA were positive in no less than 72.72% of cases, arguing for the fact that they were one of major nephritogenic antibodies. Considering the correlation analysis, no correlation between pathohistological findings and serum creatinine level was found, but there was the correlation between pathohistological findings and decreased creatinine clearance rate. The correlation between pathohistological findings and proteinuria up to 0.5 g/24 hrs was verified. There was no correlation between the increased IgG level and kidney biopsy findings, but it was found that decreased level of C4 complement component correlated with the degree of kidney lesion. The value of diastolic pressure also correlated with pathohistological findings. Concerning the applied mode of treatment, 46.55% of patients were administered pulse doses of cyclophosphamide combined with pulse doses of methylprednisolone, 5.17% had pulse doses of cyclophosphamide and 32.76% pulse doses of methylprednisolone, while 12.07% received glucocorticoid drugs combined with azathioprine, and glucocorticoids only were given to 3.45% of them. The conclusion will be that the biopsy of kidneys is the imperative in the evaluation of lupus nephritis, because the complete insight into the degree and type of kidney lesion as well as search for an optimal mode of treatment may be achieved only by assessment of combined clinical, laboratory and morphological parameters.