Serum cystatin C as a measure of GFR in renal transplant patients

• Published in: Srpski arhiv za celokupno lekarstvo Vol. 131; no. 5-6; pp. 211 - 214
• Main Authors: Jovanovic, Dijana, Krstivojevic, Pavle, Obradovic, Ivana, Djurdjevic, Vesna, Blagojevic-Lazic, Radmila, Djukanovic, Ljubica
• Format: Journal Article
• Language: English
• Published: Serbian Medical Society 2003
• Subjects: cystatin C; measure of glomerular filtration rate (GFR); renal transplant patients; ß2-microglobulin
• ISSN: 0370-8179; 2406-0895
• DOI: 10.2298/SARH0306211J

INTRODUCTION Assessment of renal function is of great importance in clinical medicine, especially in renal transplant patients requiring frequent controls of renal function. Therefore, continuous efforts have been made in searching precise and simple method for determination of glomerular filtration rate (GFR). Serum level of cystatin C (CyC), protein of low molecular weight, has been proposed as measure of GFR, but the data of its value in renal transplant patients are scarce [8-10]. PURPOSE The aim of this study was to compare the serum levels of low molecular weight proteins CyC and ?2-microglobulin (?2-MG) with creatinine clearance, as well known measure of GFR, in renal transplant patients and control group of patients with different renal disease. PATIENTS AND METHODS The study included 36 patients divided into two groups. Group 1: 20 renal transplant patients (12 men and 8 women) aged between 22 and 63 (40.4?10.1) years with creatinine clearance from 7.1 to 77.7 ml/min. Group 2: 16 controls (5 men and 11 women) with various renal diseases, aged between 24 and 63 (41.5?12.5) years with creatinine clearance from 60.5 to 116.8 ml/min. N Latex Cystatin C and ?2-microglobulin for the Behring Nephelometer System was used in this study. Creatinine was determined with Jaffe-reaction in serum and urine. RESULTS In renal transplant patients as well as in control group of patients the significant correlation between creatinine clearance and reciprocal values of the serum CyC (rt=0.828; pt<0.001; rc=0.603; pc<0.05) and reciprocal values of the serum ?2-MG levels (rt=0.791; pt<0.001; rc=0.627 pc<0.05) was found (Graph 1). There was a slightly better correlation between creatinine clearance and reciprocal values of the serum CyC than the one between creatinine clearance and reciprocal values of the serum ?2-MG without statistical significance in renal transplant patients. There was no difference in correlation coefficients between both low molecular weight proteins and creatinine clearance in Group 2. The correlation coefficient between serum CyC and ?2-MG was r=0.839(p<0.001)in renal transplant patients and r=0.835 (p<0.05) in control group. There were no significant differences in correlation coefficients between reciprocal values of serum CyC and creatinine clearance (p=0,2043) as well as reciprocal values of serum ?2-MG and creatinine clearance (p=0.3717) between Group 1 and Group 2. DISCUSSION In renal transplant patients rapid assessment of graft function is necessary. This allows early recognition of rejection as well as differential diagnosis of different renal graft disorders. Study of Risch and co [16] suggested that serum CyC was very good marker for GFR in renal transplant patients which was confirmed by the other authors too [20-22]. During inflammatory process or other pathological conditions, especially during acute rejection or infections, CyC also provided precise assessment of GFR while creatinine clearance varied dramatically [16], Serum concentration of ?2-MG, another low molecular weight protein, also depends both on its production rate and the GFR [5,19]. Its production is dramatically different in patients with infections [5] as well as while immunosuppressive drugs are used [16], Therefore, ?2-MG is impractical as GFR marker in patients with renal transplants. So, serum CyC was considered as better marker for GFR than ?2-MG and creatinine clearance in renal transplant patients with different complications [16], In this study serum CyC was slightly better marker for GFR than ?2-MG, without statistical significance (Graph 1). Renal transplant patients, however, were in the stable condition at the time of the study. CONCLUSION Serum CyC was moderately better marker of GFR than ?2-MG in renal transplant patients when they were in the stable condition. Serum CyC and ?2-MG were the same markers of GFR in control group of patients with various renal diseases. There was no significant difference in correlation coefficients between reciprocal values of the serum CyC and creatinine clearance (p=0.2043) as well as reciprocal values of the serum ?2-MG levels and creatinine clearance (p=0.3717) between two examined groups of patients. The studies on renal transplant patients with acute graft rejection or infections are warranted.
Odredjivanje bubrezne funkcije je od posebnog znacaja u klinickoj praksi narocito kod bolesni-ka sa transplantiranim bubregom kod kojih su neophodne ceste kontrole. Kako idealni marker za odredjivanje jacine glomerulske filtracije (JGF) jos nije pronadjen, i dalje se prave napori da se pronadje precizan i jednostavan metod za njegovo odredjivanje. Koncentracija cistatina S (CyQ u serumu proteina male molekulske mase i stabilne produkcije predlaze se kao nova mera JGF, ali podaci o njegovoj upotrebi kod Thni su brojni.Zato je cilj ove studije bio da se uporedi koncentracija SuSi 82-mikroglobulina (B2-MG) sa klirensom kreatinina (Ccr), kao merom JGF kod bolesnika sa transplantiranim bubregom. U studiju je ukljuceno 20 bolesnika sa transplantiranim bubregom (12 muskaraca i osam zena)starosti od 22 do 63 godine(40,4?10,1)sa Ccr od 7,1 do 77,7 ml/min i 16 bolesnika kontrolne grupe (pet muskaraca i jedanaest zena) sa razlicitim bubreznim bolestima, starosti od 24 do 63 godine(41,5?12,5), sa Ccr od 60,5 do 116,8 ml/min. Ccr je uporedjen sa reciprocnom vrednosti SuS (1/CyQ i reciprocnom vrednosti B2-MG (MB2-MG) koriscenjem metode linearne regresije. Kod bolesnika sa transplantiranim bubregom postoji znacajna korelacija izmedju Sspl 1/SuSu serumu(g=0,828;r<0,001),odnosno 1 //J2-MGu serumu (r=0,791;r<0,001), stoj e vidjeno i u kontrolnoj grupi bolesnika (SuS r=0,603;p<0,05), (B2-MG:r=0,627;p<0,05). Korelacija izmedju Ccr i 1/SuSje veca nego izmedju Sspl 1/B2-MG, ali bez statisticke znacajnosti. Koeficijent korelacije izmedju SuSi B2-MG bioje r=0,839 (r<0,001) kod bolesnika sa transplantiranim bubregom, odnosno r=0,835 (r<0,05) kod bolesnika kontrolne grupe. Nije bilo razlike izmedju ovih pokazatelja u dve ispitane grupe bolesnika. Moglo bi se zakljuciti daje koncentracija SuSu serumu nesto bolje merilo JGF nego B2-MG kod bolesnika sa transplantiranim bubregom u stabil-noj fazi, sto nije slucaj kod kontrolne grupe bolesnika. Ovo zahteva dalje ispitivanje kod bolesnika sa transplan-tiranim bubregom i akutnim pogorsanjem funkcije grafta.