LABORATORY IMMUNOLOGY AND KIDNEY TRANSPLANTATION

E. Hur¹, C. Sen², A. Nart³, S. Sen⁴, A. Akgun², F.A. Tasli⁵, M. Yilmaz¹, A. Uslu³, H. Toz^1
1Nephrology, Ege University Medical School, Izmir/TURKEY, ²Nucleer Medicine, Ege University Medical School, Izmir/TURKEY, ³Clinics Of General Surgery, Izmir Training Hospital, Izmir/TURKEY, ⁴Pathology, Ege University Medical School, Izmir/TURKEY, ⁵Clinics Of Pathology, Izmir Training Hospital, Izmir/TURKEY

Body: Introduction: To assess post transplant (tx) allograft function, serum creatinine and creatinine-based estimations of glomerular filtration rate (eGFR) has some limitations. The aim of this prospective study is to compare the serum creatinine and cystatin C-based eGFR equations with measured GFR (mGFR) and histopathologic alterations within the post tx 6 month. Method: Twenty seven adult patients (serum creatinine level <2mg/dL, proteinuria <0.5gr/day and normal thyroid function tests at post-tx 3^rd month) were included. All were receiving calcineurin inhibitor treatment and trimethoprim-sulphametoxazole prophylaxis. GFR was measured with Tc-99m DTPA double blood sampling clearance method at post tx 3^rd and 6^th months. Biochemical tests including creatinine and cystatin C were measured monthly between 3^rd and 6^th months. Nephelometric method (Dade Behring) was used for Cystatin C determination. Cockroft Gault (CG) and MDRD equations were used for creatinine based eGFR. Le Bricon, Larsson, Filler and Hoek formulations were used for cystatin C-based eGFR. Bias was defined as the mean difference between mGFR and eGFR. Accuracy was defined as the proportion of eGFR values within 30% of the mGFR. Implantation (zero-hour) and 6^th month allograft protocol biopsies were performed. Banff classification was used for the histopathological evaluation. Interstitial fibrosis (ci) and tubular atrophy (ct) were scored. Delta ci+ct (ci+ct score difference between protocol biopsies) ≥1 was accepted as progressive fibrosis. Results: Of the 27 patients, 16 were male and 15 had deceased tx. Mean creatinine, cystatin C and mGFR values were 1.08±0.32 mg/dL, 1.3±0.43mg/dL and 53.15±16.1 ml/min/1.73m² at the 3^rd month; and 1.1±0.37 mg/dL, 1.3±0.39 mg/dL and 48.81±15.71 ml/min/1.73m² at the 6^th month. mGFR values at the 3^rd and 6^th months were strongly correlated with cystatin C and creatinine values and, Hoek, Larsson, Le Bricon, MDRD and CG estimations. At the 3rd and 6th months; bias for Hoek was -10±16 and -14±11 ml/min/1.73 m² and accuracy was 59% and 77%, respectively. In progressor and nonprogressor groups, Δ mGFR (6^th-3^rd month) was -10±6 and -2.3±9.9 ml/min/1.73 m², respectively (p: 0.025), whereas Δ eGFRs derived from both creatinine and cystatin C did not reach statistical significance. Conclusion: For the assessment of early post tx allograft function, cystatin C-based GFR estimations are more reliable than creatinine-based formulas. Hoek formulation has the lowest bias and highest accuracy. Neither creatinine nor cystatin based formulations are sensitive enough for the detection of subclinical and mild graft fibrosis. Table: Mean, bias, accuracy of creatinine and cystatin C estimates

Disclosure: All authors have declared no conflicts of interest.