Os níveis séricos de cistatina C sofrem infl uência da dose de corticoide em pacientes com nefrite lúpica?Are serum cystatin C levels infl uenced by steroid doses in lupus nephritis patients? 307 Do steroid doses affect serum cystatin C levels?
J Bras Nefrol 2011;33(3):306-312
IntroductIonThere are many markers and methods to estimate renal function, and the gold standard used to determine glomerular filtration rate (GFR) is the measure of the clearances of exogenous substances, such as inulin, iohexol, Cr 5 ¹-EDTA, Tc 99 -DTPA and I 125 -iothalamate. 1 On the other hand, urea and creatinine serum (sCreat) levels are endogenous markers of renal function frequently used, but they present several limitations. 1,2 The inexistence of an ideal index of renal function, which is easily applicable in daily practice, imposes the search for new substances. 3 Serum cystatin C (sCysC) has been proposed as a promising marker of the GFR and it is seen as equivalent or even superior to sCreat. [4][5][6] However, it is not clear if other factors beyond renal function have an influence on sCysC levels. Initially, it was accepted there were not in vivo factors that could have interference on its levels. 7 Nevertheless, since its clinical application was initiated, conditions that could interfere on its serum concentration beyond renal function were reported, as corticosteroid therapy, thyroid dysfunction, chronic liver disease, malignancies, organ transplantation, and many others. 1,[8][9][10][11][12][13][14][15][16][17][18][19][20] In addition, some authors consider the possibility that sCysC values could be increased in the event of male gender, increasing age, weight, and height. Moreover, its levels could be influenced by smoking, similarly to C-reactive protein, as a marker of inflammation and cardiovascular mortality. [21][22][23][24] In fact, the superiority of sCysC over sCreat in the evaluation of GFR was demonstrated in some circumstances, but it is still questionable whether nonrenal factors could interfere on its levels, as the use of glucocorticoids. [7][8][9][10][11][12][13] The aim of this study is to evaluate whether corticosteroids have an influence on sCysC levels. In order to test this hypothesis, we evaluated patients with lupus nephritis using different doses of PO and IV glucocorticoids.
SubjectS and methodSForty-two patients with systemic lupus erythematosus (SLE), which diagnosis was established by the presence of at least four criteria of angiotensin receptor antagonists (ARA), 25 were enrolled, and 109 blood samples were collected. These patients were followed in the Glomerulopathy Section (Division of Nephrology) of Universidade Federal de São Paulo (UNIFESP). All of them had renal involvement during the course of SLE. Patients with a previous renal biopsy were classified according to the World Health Organization (WHO) Lupus Nephritis Classification. 26 The study was approved by the Ethics Committee, and patients were included in the study after signing their informed consent.All patients included in t...