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Introduction: Steroid-based immunosuppression after transplantation increases the risk of post-transplant diabetes mellitus (PTDM), with adverse effects on patient and graft survival. In the SAILOR study, we investigated the safety and efficacy of complete steroid avoidance in immunologically low-risk kidney recipients without diabetes on the current standard-of-care maintenance regimen with tacrolimus/mycophenolate mofetil (MMF). Methods: In this 2-year, multicenter, open-label trial, a total of 222 patients were randomized to receive either steroid avoidance protocol (tacrolimus/MMF/antithymocyte globulin [ATG] induction [n = 113]) or steroid maintenance protocol (tacrolimus/MMF/prednisolone/basiliximab-induction [n = 109]). Results: At 1 year, no significant differences were found between steroid avoidance and steroid maintenance arms in the incidence of PTDM, the primary end point (12.4% vs. 18.3%, respectively, P = 0.30, CI: 16.3–4.4), or in overall biopsy-proven rejections (15% vs. 13.8%, respectively, P = 0.85). At 2 years, the composite end point of freedom from acute rejection, graft loss, and death (81% vs. 85%, respectively, P = 0.4), kidney function, or adverse events was comparable between the 2 arms. Moreover, 63.9% of the patients in the steroid avoidance arm remained free from steroids at 2 years. Conclusion: The SAILOR study provides further evidence for the feasibility, safety, and efficacy of early steroid-free treatment at 2 years in immunologically low-risk kidney recipients with tacrolimus/MMF maintenance regimen.

BACKGROUND: Solid organ transplant (SOT) recipients may be more vulnerable to coronavirus disease 2019 (COVID-19). Data on the clinical course of COVID-19 in immunosuppressed patients are limited, and the optimal management strategy for these patients is yet unclear. METHODS: We present 53 SOT recipients (31 kidney transplant recipients, 8 liver transplant recipients, 5 heart transplant recipients, 5 lung transplant recipients, 3 liver-kidney transplant recipients, and 1 kidney-after-heart transplant recipient), transplanted at a Swedish high-volume transplant center and each diagnosed with COVID-19 between February 21, 2020 and June 22, 2020. Demographic, clinical, and treatment data were extracted from the electronic patient files. RESULTS: Patients reported fever (61%), cough (43%), diarrhea (31%), and upper respiratory symptoms (29%). The median age was 56 years, and 57% were male. According to severity, 55% had mild, 13% had moderate, 19% had severe, and 13% had critical disease. Thirty-seven patients (70%) were hospitalized, with 8 requiring intensive care. Thirteen of the 37 patients were initially managed as outpatients but later hospitalized. One patient received hydroxychloroquine, and no patients received antivirals. Antimetabolites and calcineurin inhibitors were held or reduced in two-thirds. Twenty-seven of 37 hospitalized patients (73%) received low-molecular-weight heparin. Five (13.5%) hospitalized patients died. Overall survival for the entire cohort was 90.5%. No rejection episodes were noted. CONCLUSIONS: Hospitalization, lowering of immunosuppression, and prophylactic anticoagulation were the most common therapeutic interventions for SOT recipients with COVID-19. A significant proportion of patients could be managed on an outpatient basis, while keeping a low threshold for admission. Mild and moderate disease forms seem to have a good outcome. (Less)

Introduction The proof-of-concept of uterus transplantation, as a treatment for absolute uterine factor infertility, came with the first live birth after uterus transplantation, which took place in Sweden in 2014. This was after a live donor procedure, with laparotomy in both donor and recipient. In our second, ongoing trial we introduced a robotic-assisted laparoscopic surgery of the donor to develop minimal invasive surgery for this procedure. Here, we report the surgery and pregnancy behind the first live birth from that trial. Material and methods In the present study, within a prospective observational study, a 62-year-old mother was the uterus donor and her 33-year-old daughter with uterine absence as part of the Mayer-Rokitansky-Kuster-Hauser syndrome, was the recipient. Donor surgery was mainly done by robotic-assisted laparoscopy, involving dissections of the utero-vaginal fossa, arteries and ureters. The last part of surgery was by laparotomy. Recipient laparotomy included vascular anastomoses to the external iliac vessels. Data relating to in vitro fertilization, surgery, follow up, obstetrics and postnatal growth are presented. Results Three in vitro fertilization cycles prior to transplantation gave 12 cryopreserved embryos. The surgical time of the donor in the robot was 360 minutes, according to protocol. The durations for robotic surgery for dissections of the utero-vaginal fossa, arteries and ureters were 30, 160 and 84 minutes, respectively. The remainder of donor surgery was by laparotomy. Recipient surgery included preparations of the vaginal vault, three end-to-side anastomoses (one arterial, two venous) on each side to the external iliacs and fixation of the uterus. Ten months after transplantation, one blastocyst was transferred and resulted in pregnancy, which proceeded uneventfully until elective cesarean section in week 36+1 . A healthy boy (Apgar 9-10-10) was delivered. Follow up of child has been uneventful for 12 months. Conclusions This is the first report of a live birth after use of robotic-assisted laparoscopy in uterus transplantation and is thereby a proof-of-concept of use of minimal invasive surgery in this new type of transplantation.

Background: Mycophenolic acid (MPA) is a potent immunosuppressive agent used in solid organ transplantation. MPA exhibits large interindividual variation in dose-normalized plasma concentrations but is nevertheless usually prescribed as a fixed dose without use of therapeutic drug monitoring (TDM). Data on the effect of corticosteroid (CS) treatment on MPA concentrations during concomitant tacrolimus treatment remains sparse.Methods: Data is based on TDM of MPA area under the concentration curve (AUC) in 210 renal transplant recipients participating in the prospective, randomized, controlled, multi-center trial (SAILOR) where a steroid-free immunosuppressive regimen with mycophenolate mofetil (MMF) and low-dose tacrolimus was compared with a conventional prednisolone-based treatment regimen. Multilevel mixed-effects linear regression post-hoc analyses of MPA AUC was performed.Results: Median MPA AUC at baseline (within the first 2 weeks post-transplant) in patients taking 2 g MMF daily was 53 mg*h/L (interquartile range: 43–69 mg*h/L, min: 24—max: 117 mg*h/L). Between-patient variation in MPA AUC was up to 5-fold on the same MMF dose. Patients in the steroid-free group had 12.5% lower (95% CI; 3.2–20.9%, p = 0.01) MPA AUC levels at baseline compared to the steroid treated group. During follow-up (14 days–2 years post-transplant) there were no significant differences in MPA AUC between the groups with MPA AUC being 4.2% lower (95% CI: −4.8%−12,5%, p = 0.35) in the steroid-free vs standard treatment group in restricted analysis after multivariate adjustment for tacrolimus trough level, body weight, time after transplantation and MMF dose. MMF dose was positively correlated with MPA AUC (p < 0.001) whereas body weight was negatively correlated with MPA AUC (p < 0.001). MPA AUC was 0.4% (95% CI: 0.2–0.6%, p < 0.001) lower per 1 kg increase in weight. Tacrolimus trough levels had no significant effect on MPA AUC.Conclusion: Immunosuppression with CS during concomitant tacrolimus treatment was shortly after transplantation associated with a significantly higher MPA exposure but the effect was small and not maintained during follow-up. Low body weight was associated with higher MPA exposure, which suggests a potential for weight adjusted MMF dosing.

Solid organ transplant (SOT) recipients may be more vulnerable to coronavirus disease 2019 (COVID-19). Data on the clinical course of COVID-19 in immunosuppressed patients are limited, and the optimal management strategy for these patients is yet unclear.We present 53 SOT recipients (31 kidney transplant recipients, 8 liver transplant recipients, 5 heart transplant recipients, 5 lung transplant recipients, 3 liver-kidney transplant recipients, and 1 kidney-after-heart transplant recipient), transplanted at a Swedish high-volume transplant center and each diagnosed with COVID-19 between February 21, 2020 and June 22, 2020. Demographic, clinical, and treatment data were extracted from the electronic patient files.Patients reported fever (61%), cough (43%), diarrhea (31%), and upper respiratory symptoms (29%). The median age was 56 years, and 57% were male. According to severity, 55% had mild, 13% had moderate, 19% had severe, and 13% had critical disease. Thirty-seven patients (70%) were hospitalized, with 8 requiring intensive care. Thirteen of the 37 patients were initially managed as outpatients but later hospitalized. One patient received hydroxychloroquine, and no patients received antivirals. Antimetabolites and calcineurin inhibitors were held or reduced in two-thirds. Twenty-seven of 37 hospitalized patients (73%) received low-molecular-weight heparin. Five (13.5%) hospitalized patients died. Overall survival for the entire cohort was 90.5%. No rejection episodes were noted.Hospitalization, lowering of immunosuppression, and prophylactic anticoagulation were the most common therapeutic interventions for SOT recipients with COVID-19. A significant proportion of patients could be managed on an outpatient basis, while keeping a low threshold for admission. Mild and moderate disease forms seem to have a good outcome.

Uterus transplantation has proved to be a feasible treatment for uterine factor infertility. Herein, we report on recipient outcome in the robotic uterus transplantation trial of 2017&ndash, 2019. The eight recipients had congenital uterine aplasia. The donors were six mothers, one sister, and one family friend. Donor surgery was by robotic-assisted laparoscopy. Recipient surgery was by laparotomy and vascular anastomoses to the external iliacs. The duration (median (ranges)) of recipient surgery, blood loss, measured (left/right) uterine artery blood flow after reperfusion, and length of hospital stay were 5.15 h (4.5&ndash, 6.6), 300 mL (150&ndash, 600), 43.5 mL/min (20&ndash, 125)/37.5 mL/min (10&ndash, 98), and 6 days (5&ndash, 9), respectively. Postoperative uterine perfusion evaluated by color Doppler showed open anastomoses but restricted blood distribution in two cases. Repeated cervical biopsies in these two cases initially showed ischemia and, later, necrosis. Endometrial growth was not seen, and hysterectomy was later performed, with pathology showing partly viable myometrium and fibrosis but necrosis towards the cavity. The other six patients acquired regular menstrual cyclicity. Surgery was performed in two patients to correct vaginal stenosis. Reversible rejection episodes were seen in two patients. In conclusion, the rate of viable uterine grafts during the initial 6-months of the present study (75%) leaves room for improvement in the inclusion/exclusion criteria of donors and in surgical techniques. Initial low blood flow may indicate subsequent graft failure.

STUDY QUESTION What are the costs of live donor uterus transplantation in a European setting? SUMMARY ANSWER The total costs for preoperative investigations, including IVF, and live donor uterus transplantation including postoperative costs for 2 months, were calculated to be €74 564 (mean), with the costs of recipient being somewhat higher than for donor and the cost components of total costs distributed between sick leave (25.7%), postoperative hospitalization (17.8%), surgery (17.1%), preoperative investigations (15.7%), anaesthesia (9.7%), drugs (7.8%), tests after surgery (4.0%) and for re-hospitalization (2.2%). WHAT IS KNOWN ALREADY Uterus transplantation has proved to be successful by demonstrations of live births, both after live donor and deceased donor procedures. The transplantation is considered as a complex and expensive infertility treatment. There exist no analyses of costs involved in uterus transplantation. STUDY DESIGN, SIZE, DURATION This prospective cohort study included nine uterus transplantations procedures, performed in Sweden in 2013. Study duration of this health economic study included 6–12 months of pre-transplantation investigations and the time interval from transplantation to 2 months after. PARTICIPANTS/MATERIALS, SETTING, METHODS Nine triads of uterus recipient, partner of recipient and uterus donor participated. All prospective recipients were in stable relationships and performed IVF with their partners before transplantation. The nine donors were relatives or family friends. The recipients and donors underwent pre-transplantation investigations with imaging, laboratory tests and psychological/medical screening prior to transplantation. Transplantation was by laparotomy in both donor and recipient. Standard immunosuppression and postoperative medication were used. After discharge from the hospital, the recipients were followed frequently with laboratory tests and examinations. MAIN RESULTS AND THE ROLE OF CHANCE The mean costs for preoperative investigations, including IVF, and live donor uterus transplantation with postoperative costs for 2 months, were calculated to be €74 564 (range €50 960–€99 658), from a societal perspective. The four largest components were cost of sick leave (€19 164), cost of postoperative hospitalization (€13 246), surgery cost (€12 779) and costs for preoperative investigations, including IVF (€11 739). Smaller components were costs for anaesthesia (€7207), costs for drugs (€5821), costs for post-surgical tests (€2985) and costs for re-hospitalization (€1623). The costs of the recipient (€42 984) were somewhat higher than the costs of the donor (€31 580), but in terms of costs, they should be viewed as one entity. By using a health care perspective, excluding cost for productivity loss, the total costs would be reduced by 26%. LIMITATIONS, REASONS FOR CAUTION A limitation is the restricted sample size and that this is in the experimental, clinical stage of development. WIDER IMPLICATIONS OF THE FINDINGS The results provide the first information concerning the costs for pre-transplantation investigations and uterus transplantation procedures with postoperative follow-up. We consider the total estimate to be in the higher interval, because of the extensive research protocol. It is likely that the cost of live donor uterus transplantation will vary between countries and that the costs will be lower in a future clinical setting. STUDY FUNDING/COMPETING INTEREST(S) Funding was received from the Jane and Dan Olsson Foundation for Science; the Knut and Alice Wallenberg Foundation; an ALF grant from the Swedish state under an agreement between the government and the county councils; and the Swedish Research Council. None of the authors have a conflict of interest with regard to the study. TRIAL REGISTRATION NUMBER NCT01844362.

Uterus transplantation has enabled women with absolute uterine factor infertility to carry a pregnancy. The first human uterus transplantation trial was initiated in 2013 in Gothenburg, Sweden. It was completed with 7 transplantations with long-term allograft survival and 9 children born from 6 women. In the present study we describe the histopathology of these 7 allografts, which were removed at 22-83 months after transplantation, and compare findings to control cases. Morphological findings in a subset of explants included linear subepithelial inflammation and perivascular stromal inflammation in the cervix, small inflammatory foci in the myometrium, and intimal inflammation in larger arteries. The average number of T cells, B cells, and macrophages was higher in transplants compared to normal controls, but variability was high among transplants. Chronic-active vascular rejection was seen in 2 of 7 transplants, both showed also inflammation in the cervix. Further, the inflammation seen in the cervix reflected the inflammation in the myometrium, suggesting that cervical biopsies are suitable to monitor rejection. However, the degree of inflammation and signs of rejection in explants did not reflect on the possibility to become pregnant in this limited series.

Uterus transplantation has recently been introduced as a novel infertility treatment in a small number of centers around the world. In this chapter, the immunosuppressive armamentarium at our current disposal will be discussed. We will also examine recent immunosuppression protocols employed as induction, maintenance, and rejection treatment for uterus transplantation and discuss specific aspects of immunosuppression during pregnancy. Moreover, future aspects of immunosuppression in uterus transplantation will be discussed.

Objective To determine whether a uterus from the mother of a woman with absolute uterine factor infertility can be transplanted to daughter and carry a pregnancy with delivery of a healthy child. Design Part of an observational study. Setting University teaching hospital. Patient(s) Twenty eight-year-old woman with uterine agenesis, her male partner, and her 50-year-old mother. Intervention(s) In vitro fertilization with embryo cryopreservation before live donor uterus transplantation (UTx). Induction immunosuppression. Embryo transfer 12 months after UTx, pregnancy controls, delivery, and hysterectomy. Main Outcome Measure(s) Results of IVF-ET, parameters of pregnancy/birth, and surgical data of transplantation/cesarean section/hysterectomy. Result(s) Two IVF cycles before UTx resulted in 10 cryopreserved embryos. Donor surgery included hysterectomy with vascular pedicles of uterine vessels and proximal vessels up to and including parts of internal iliacs. Recipient surgery was by bilateral vascular connections to external iliacs, vaginal–vaginal anastomosis, and uterine fixation. Pregnancy occurred at the first single ET, and the pregnancy proceeded uneventfully until gestational week 34, when the patient developed cholestasis with intense pruritus. Cesarean section was performed at 34+6, with delivery of a healthy boy (weight 2,335 g). Hysterectomy was performed 3.5 months after delivery. The weight of the healthy child at 12 months was 9.3 kg. Grandmother (uterus donor) and mother are in good health 3 years after UTx. Conclusion(s) This is the first report of a live birth after mother-to-daughter UTx, and it also represents the second birth ever after human UTx. Clinical Trial Registration NCT01844362.

Background In Sweden, native and transplant kidney biopsies are usually performed in major renal medical centers. Purpose To clarify risk factors in native and transplant kidney biopsies to improve patient safety. Material and Methods A total of 1001 biopsies (in 352 women and 565 men) were included. The median age was 54 years (range, 16–90 years). Data were derived from 826 native kidney biopsies (640 prospective and 186 retrospective) and 175 transplant kidney biopsies (170 prospective and 5 retrospective). Various factors and complications were registered while performing native and transplant kidney biopsies, focusing on major (e.g. blood transfusions, invasive procedures) and minor complications. The prospective protocol was used at six centers and at one center data were obtained retrospectively. Results Women were at greater risk of overall complications than men (12.2% vs. 6.5%; P = 0.003; odds ratio [OR], 2.0; confidence interval [CI], 1.3–3.1) as well as of major complications (9.6% vs. 4.5%; P = 0.002; OR, 2.2, CI 1.3–3.7). Major complications occurred more commonly after biopsies from the right kidney, in women than in men (10.8% vs. 3.1%; P = 0.005; OR, 3.7; CI, 1.5–9.5), and in patients with lower BMI (25.5 vs. 27.3, P = 0.016) and of younger age (45 years vs. 52.5 years; P = 0.001). Lower mean arterial pressure in transplant kidney biopsies indicated a risk of major complications (90 mmHg vs. 98 mmHg; P = 0.039). Factors such as needle size, number of passes, serum creatinine, and eGFR did not influence complication rates. Conclusion The present findings motivate greater attention being paid to the risk of major side-effects after right-side biopsies from women’s kidneys, as well as after biopsies from younger patients and patients with lower BMI.

Until now, absolute uterine factor infertility has been the major untreatable form of female infertility. Uterus transplantation has recently proven to be the first successful treatment for absolute uterine factor infertility, with demonstration of live births. In this study, live donation uterus transplantation was performed in nine women. In total, 163 cervical biopsies (149 protocol, 14 follow-up) were taken to detect histopathological signs of rejection. Based on experience from animal experiments, we used a three-grade scoring system to evaluate biopsies systematically. Nine episodes of rejection were diagnosed in five patients: grade 1 in six episodes, grade 2 in two episodes, and grade 3 in one episode. Treatment decisions were based on histopathology, and all rejection episodes were reversed after treatment. The biopsies were reviewed retrospectively, and immunohistochemistry was performed to characterize the inflammatory infiltrates. A borderline category was introduced to avoid overtreatment of patients. Based on our review of all biopsies, we put forward a simple grading system for monitoring of rejection and to guide immunosuppressive treatment in uterus transplantation.

Prior research on donor monoclonal gammopathy of undetermined significance (MGUS) has been inadequate regarding the risk for lymphoproliferative disease in solid organ transplantation recipients. Seven organ recipients from two different donors developed lymphoproliferative disease. The origin of the malignancy was determined by use of microsatellite analysis, and the plasma of the two donors was analyzed with the use of electrophoresis. The clinical courses of the seven recipients were followed for 36-60 months. One donor transmitted lymphoplasmacytic lymphoma to two kidney recipients and MGUS to a liver recipient, all IgMκ. A second donor caused IgGλ myeloma in two kidney and one liver recipient, and IgGλ gammopathy in a heart recipient. Transplant nephrectomy was performed in three kidney recipients and remission was achieved. The fourth kidney recipient has kept the graft and the disease has progressed. The liver recipient died from myeloma. There were no clinical signs of lymphoproliferative disease in the donors, but retrospective serum analyses showed M-components, IgMκ (37 g/L) and IgGλ (8 g/L). Donors with MGUS may cause donor-transmitted malignancies via passenger lymphocytes/plasma cells in solid organ recipients. The results call for a large register study of the incidence of donor MGUS and lymphoproliferative disease in their recipients.

Uterus transplantation is the first available treatment for absolute uterine infertility, which is caused by absence of the uterus or the presence of a non-functional uterus. Eleven human uterus transplantation attempts have been done worldwide but no livebirth has yet been reported.In 2013, a 35-year-old woman with congenital absence of the uterus (Rokitansky syndrome) underwent transplantation of the uterus in Sahlgrenska University Hospital, Gothenburg, Sweden. The uterus was donated from a living, 61-year-old, two-parous woman. In-vitro fertilisation treatment of the recipient and her partner had been done before transplantation, from which 11 embryos were cryopreserved.The recipient and the donor had essentially uneventful postoperative recoveries. The recipient's first menstruation occurred 43 days after transplantation and she continued to menstruate at regular intervals of between 26 and 36 days (median 32 days). 1 year after transplantation, the recipient underwent her first single embryo transfer, which resulted in pregnancy. She was then given triple immunosuppression (tacrolimus, azathioprine, and corticosteroids), which was continued throughout pregnancy. She had three episodes of mild rejection, one of which occurred during pregnancy. These episodes were all reversed by corticosteroid treatment. Fetal growth parameters and blood flows of the uterine arteries and umbilical cord were normal throughout pregnancy. The patient was admitted with pre-eclampsia at 31 full weeks and 5 days, and 16 h later a caesarean section was done because of abnormal cardiotocography. A male baby with a normal birthweight for gestational age (1775 g) and with APGAR scores 9, 9, 10 was born.We describe the first livebirth after uterus transplantation. This report is a proof-of-concept for uterus transplantation as a treatment for uterine factor infertility. Furthermore, the results show the feasibility of live uterus donation, even from a postmenopausal donor.Jane and Dan Olsson Foundation for Science.

BACKGROUND: Corticosteroids and calcineurin inhibitors (CNIs) are included in renal transplantation immunosuppressive protocols around the world. Well-known side effects are associated with the use of these drugs, including new onset of diabetes after transplantation (NODAT). Long-term patient survival rates are lower among patients with NODAT. The optimal immunosuppressive protocol would therefore include not using corticosteroids and minimization of CNI use.METHODS/DESIGN: This is a prospective, multi-centre, controlled, randomized, parallel group, open-label study involving kidney transplant patients. The study compares a steroid-free immunosuppressive protocol (study arm A), which is based on low-dose tacrolimus and mycophenolate mofetil (MMF) maintenance therapy together with antithymocyte globulin (ATG) induction, with the conventional immunosuppressive protocol (study arm B), being based on low-dose tacrolimus, MMF and steroids together with interleukin-2 receptor (IL2-R) induction. The study is designed to include most normal-risk patients. It will exclude patients seen as at a high risk of rejection. The primary objective of the study is to assess the cumulative incidence of NODAT in the two study arms 12 months after transplantation using the American Diabetes Association type 2 diabetes diagnostic criteria. The composite measure of freedom from acute rejection, graft survival and patient survival will be evaluated. Renal function and chronic changes in the transplanted kidney will be assessed.DISCUSSION: If this study confirms conceptual expectations, namely decreased incidence of NODAT, the steroid-free study protocol could be used with all patients. The regimen could be especially beneficial for patients at a high risk of diabetes mellitus.TRIAL REGISTRATION: TRIAL REGISTRATION: EudraCT 2012-000451-13.

Vascular changes are considered the major histopathological indicator of chronic allograft dysfunction. These changes are characterized by intimal thickening caused by accumulation of primarily smooth muscle cells. Contributing factors may be of both immunological and nonimmunological origin. Cold ischemia has been shown to trigger intimal proliferation in the absence of alloantigen in an isogenic rat aortic transplant model. We have used this model to investigate the impact of inhibition of tissue factor (TF) signalling on the progression of intimal thickening. Group 1 was treated with recombinant FVIIa inhibited in its active site (rFVIIai), and group 2 served as untreated controls. At 8 weeks the intimal area was measured with image analysis. Medial areas and the proportion of medial necrosis were determined. Animals treated with rFVIIai showed significantly less intimal thickening compared with controls: median 0.147 vs. 0.256 mm2, respectively (p = 0.008). A positive correlation between intimal hyperplasia and medial necrosis (r(s) = 0.79, p = 0.01), as well as adventitial inflammation (r(s) = 0.83, p = 0.009), was found. TF mRNA was not detected in the neointima at 8 weeks, as determined by in situ hybridization. We conclude that active site inhibited FVIIa (rFVIIai) given prior to and directly after implantation of aortic transplants significantly reduces intimal hyperplasia caused by nonimmunological factors in this model.

Background/Aims: Serum creatinine has several drawbacks as marker of glomerular filtration rate (GFR), and therefore serum cystatin C has been proposed as a more optimal GFR marker. Previous reports have suggested benefits of serum cystatin C measurements in patients with renal transplants. The purpose of the present study was to evaluate the diagnostic accuracy of cystatin C measurements compared with enzymatic creatinine measurements as serum markers of GFR (established from plasma clearance of iohexol) in a large cohort of stable renal transplant recipients and in the early postoperative phase. Methods: Renal transplant patients (n = 125) with stable graft function were evaluated from reciprocals of serum creatinine and cystatin C compared with iohexol clearance. Fourteen patients were examined immediately after the onset of renal function. Cystatin C was measured by a particle-enhanced turbidimetric method and creatinine by an enzymatic method. Results: In stable renal transplant recipients, serum cystatin C showed a significantly (p = 0.033) closer correlation (r = 0.89 or 79% co-variance) with iohexol clearance than did serum creatinine (r = 0.81 or 66% co-variance). Using the χ2 test and a cut-off at 60 ml/min/1.73 m2, serum cystatin C levels demonstrated significantly higher sensitivity for early GFR impairment (p = 0.0045) compared with serum creatinine measurements. On the first day after transplantation, serum cystatin C fell more rapidly than serum creatinine. Conclusion: Serum cystatin C levels correlate significantly closer to accurate measurements of GFR and are significantly more sensitive to detect early GFR impairment than enzymatic measurements of creatinine in serum.