Correlation of Tough Tacrolimus Level with Early Acute Rejections in Renal Allograft Recipients- A Prospective Study Volume 1 - Issue 3

Manish Tripathi*, Kalpesh Gohel, Umapati Hegde, Sishir Gang and Mohan Rajapurkar

• Department of Nephrology, Muljibhai Patel Urological Hospital and Society for Research in Nephro-Urology, India

Received: January 03,2018;   Published: January 18, 2018

*Corresponding author: Manish Tripathi, Department of Nephrology, Emirates European Hospital, UAE

DOI: 10.32474/IGWHC.2018.01.000111

Abstract PDF

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Abstract

Acute Rejection is the key mediators of long term graft loss. So we aimed the present study to assess the correlation of baseline pre transplant trough tacrolimus level with early rejection. We prospectively analyzed the trough tacrolimus level on the day prior to transplantation of 179 patients transplanted from September 2007 to September 2009. We divided them into three groups according to the trough levels: Group I = < 5 ng/ml, Group II = 5-15 ng/ml and Group III = > 15ng/ml. Their demography, incidence of BPAR, NOD, infections and biopsy proven CNI toxicity were studied. Incidence of BPAR were the highest in the Group I and lowest in the Group III. None of the patients in Group III had rejection with Banff grade > 2. Incidences of post transplant at infection, new onset diabetes were comparable. Trend towards higher incidence of biopsy proven CNI toxicity was noted from Group I to Group III. These results indicate that the incidence as well as severity of early rejection reduces as the pre transplant trough tacrolimus level increases. Trend towards higher nephrotoxicity with higher trough level was noted [1-25].

Keywords: Acute rejection; Renal transplant; Pre transplant tough; Tacrolimus level; Live donors; Graft survival; Nephrotoxicity

Abbrevations: BPAR: Biopsy Proven Acute Rejection; NOD: New Onset Diabetes; CNI: Calcineurin Inhibitor; MMF: Mycophenolate Mofetil; WIT: Warm Ischemia Time; CIT: Cold Ischemia Time; PTDM: Post Transplant Diabetes Mellitus; TAC: Tacrolimus; DGF: Delayed Graft Function; OHA: Oral Hypoglycemic Agent; TMA: Thrombotic Microangiopathy; TRAS: Transplant Renal Artery Stenosis; AGE: Acute Gastroenteritis; CMV: Cytomegalo Virus; HBV: Hepatitis B Virus; HCV: Hepatitis C Virus; UTI: Urinary Tract Infection; TCMR: T Cell Mediated Rejection; AMR: Antibody Mediated Rejection; TIR: Tubulo Interstitial Rejection

Introduction

Short-term transplant outcomes have improved such that, if no rejection episodes occur, recipients of live donor grafts can now expect graft function to exceed 95% at 1 year and 90% after 5 years. Several studies have shown that acute rejection is the most significant risk factor for chronic rejection and potential surrogate for long-term graft failure. Several trials are now aimed at the reduction of early acute rejection episodes to improve long term graft survival [1-24]. Transplantation with living donor allows anticipated planning of the procedure, which can be performed before dialysis treatment, and prior administration of an immunosuppressant scheme. Pre-transplant administration of immunosuppressant aims to minimize the incidence and severity of episodes of acute rejection. The risk of acute rejection is greater in the first week post-transplant and progressively decreases after the first months. Thus, the concentration of immunosuppressive drugs must be maximal at this initial phase and tapered during subsequent months, according to the evolution of patient and graft function [25-60].

Many transplantation centers advocate the administration of immunosuppressant pre-transplant, with a variation of one to five pre-operative days, while other centers only start the therapy after the surgery. The potential disadvantages of early administration of immunosuppressant therapy are the risk of infection and the nephrotoxicity effects of calcineurin inhibitors during allograft reperfusion. Up to the present moment, there is only one systematic study that addresses the impact of pre-transplant administration of immunosuppressive therapy consisting of cyclosporine as the CNI, on incidence and severity of acute rejection [60-75].

Material and Methods

Study Design

This is an open label randomized study consisting of renal allograft recipients from living donors. This study was carried out by Department of Nephrology, at a tertiary level referral hospital in western India, between January 2008 to September 2009. All patients enrolled were older than 18 years. The protocol received approval from the Ethical Committee of the hospital society. All the patients in the study received pre-transplant immunosuppressant starting 3 days prior to transplant. The follow up period was 1 year post transplant [75-90].

Immunosuppresion Scheme

Patients from the study group received Tacrolimus (0.15mg/ kg/d) divided into 2 doses and Azathioprine (2mg/kg/d), single dose, or Mycophenolate mofetil (4gm/d) divided into 2 doses, initiated 3 days pre-transplant. Methylpredn isalone (1g) was administered intravenous during surgery and after and after that, oral prednisalone was iniciated (8mg/kg/d) and gradually tapered to .3mg/kg/d after 3 months of transplant. Doses of Tacrolimus were adjusted according to the 12-hr trough level (C min), aiming to maintain the whole blood trough level between 10-20ng/ml over the initial 3-month post transplantation period and subsequently trough levels were reduced to 5-15ng/ml. Azathiprine dose was reduced or suspended in the presence of leucopenia. The Prednisalone dose was tapered to 0.4 mg/kg/d at the end of the first month, 0.3mg/kg/d at the second month, reaching 0.2mg/ kg/d at the third month [90-115].

Clinical Assessment

Serum creatinine was determined daily during the first 10 days and on day 14, 21, 28, 45, 60, 90, 180, 240 post transplant. Cmin was measured using a semi automated fluorescence polarization immunoassay (...) Baseline trough levels were measured on day of transplant and twice/week thereafter for the first 10 days. Subsequently trough levels were measured as per graft function and clinical requirement. The diagnosis of acute rejection was based on clinical and laboratory data. Percutaneous biopsy was always performed to confirm the diagnosis. The Banff 97 classification was used to graduate rejection severity. Acute rejection treatment included methylprednisalone (500mg/d) for 3-5 days or antilymphocyte globulin (ATG) in case of severe acute rejection (Banff grade 3) or steroid resistant acute rejection. The rejection-free graft survival was defined as patients free of rejection based in clinical/laboratory and or biopsy data. Graft loss was defined by the requirement of permanent dialysis after graft failure. Delayed graft function was defined as the requirement of dialysis during the first week after transplant in the absence of rejection and or technical problems. Non- response of acute rejection to conventional therapy was considered a failure of the protocol and the reason for conversion of the immunosuppressant therapy.

Statistical Analyses

Demographic, baseline characteristics and outcome characteristics were collected throughout the first year posttransplant. Demographic data included donor and recipient age, gender, relation and underlying native kidney disease. Baseline transplant information included induction used, anti-proliferative used, number of HLA mismatches, graft renal artery number(single or dual), WIT and CIT. Data on complications was also collected including post transplant rejections, surgical complications, infections, liver dysfunctions, PTDM, TAC nephrotoxicity, and delayed graft functions(DGF). DGF was defined as need for dialysis in the first week post-transplant.

PTDM was defined as requirement for oral hypoglycemic agents or insulin for the first time post-transplant. The outcome was assessed on the incidence and severity of acute rejection in correlation to base-line trough tacrolimus level measured on day 0 of transplantation. The side-effects of the immunosuppressive therapy was also assessed in the form of; episodes of posttransplant infection and their severity; liver dysfunction; PTDM and its severity (transient or persistent; requiring OHAs or insulin). Patients were divided and analyzed in three groups based on base-line trough TAC level on day 0 post-transplant: Group 1 : TAC 0- 5 ng/ml (n = 34), Group 2 : TAC 5-15 ng/ml (n =112), Group 3 : TAC >15 ng/ml (n = 33). Simple statistical tools were used for calculating demographic parameters. The difference between the two group means was tested using Student's t-test and the presence of episode within two groups by 2x2 Chi-square test. SPSS version 15.0 was used to carry the logistic regression analysis and to find the Pearson's correlation coefficients.

Results

One hundred and seventy-nine patients were included in the study, 145 (81%) males and 34 (19%) were females. The median age of cohort was 47.35 years (range 13-65 years). Our decision to take base-line trough tacrolimus level measured on day 0 of transplantation was based on the wide-ranging TAC seen in that time frame, despite all patients receiving the same initial oral dose of 0.15 mg/kg bid being started 2 days before transplant. TAC doses were subsequently adjusted in all groups to achieve a target TAC of 12-14 ng/ml by one week post-transplant.

Baseline Demographics

Male: female ratio among recipients in Group 1 was 24:10; Group 2 was 94:18; Group 3 was 27:6. Male: female ratio among donors in Group 1 was 9:25; Group 2 was 39:73 and in Group 3 was 13:20, as shown in table 11.1 and 11.2 respectively (Tables 1-7).

Table 1: One hundred and seventy-nine patients were included in the study, 145 (81%) males and 34 (19%) were females. The median age of cohort was 47.35 years (range 13-65 years).

Table 2: Patients were divided and analyzed in three groups based on base-line trough TAC level on day 0 post-transplant: Group 1 : median TAC 3.45 ng/ml (n = 34, range 1.1-5.0 ng/ml), Group 2 : median TAC 7.7 ng/ml (n =112, range 5.1-14.9 ng/ml), Group 3 : median TAC 20.7 ng/ml (n = 33, range 15.6-36.7 ng/ ml).

Table 3.1: Ratio of related donors to unrelated donors in each in each group was: Group 1- 28:6; Group 2- 76:36; Group 3- 22:11.

Table 3.2: Ratio of related donors to unrelated donors in each in each group was: Group 1- 28:6; Group 2- 76:36; Group 3- 22:11.

Table 4: Average age of recipient age in Group 1 was 49.06 + 10.15; in Group 2 was 47.38+9.6 and in Group 3 was 46.42+10.2. Table 5 categorizes them into 3 groups i.e. <20yrs; 20-40 yrs and >40yrs.

Table 5: Average age of donor in Group 1 was 49.05 + 10.15; in Group 2 was 47.7 + 10.14 and in Group 3 was 46.42 + 10.2. This is again categorized into 3 groups.

Table 6: Average age of donor in Group 1 was 49.05 + 10.15; in Group 2 was 47.7 + 10.14 and in Group 3 was 46.42 + 10.2. This is again categorized into 3 groups.

Table 7: Total ischemia time (TIT) was comparable in all 3 groups; in Group 1 TIT was 61.32+17.58; in Group 2 TIT was 57.15+9.7 and in Group 3 was 58.42+13.61. TIT in all the groups was divided into 3 groups.

HLA Mismatch

HLA mismatch in 3 groups were as follows: Group 1 haplo match was in 9 and nil match was in 0; Group 2 haplo match was in 27 and nil match was in 5; Group 3 haplo match was in 8 and nil match was in 1 patient. Various degree of HLA mismatch in all 3 groups is as shown in Table 8.

Table 8: HLA mismatch in 3 groups were as follows: Group 1 haplo match was in 9 and nil match was in 0; Group 2 haplo match was in 27 and nil match was in 5; Group 3 haplo match was in 8 and nil match was in 1 patient. Various degree of HLA mismatch in all 3 groups.

Immunosupression

Use of induction (ATG or IL2 receptor blockers) in 3 groups was as follows: Group 1 - 15; in Group 2 - 35; in Group 3-17. Different induction protocols used in 3 groups are as shown in Tables 9 & 10.

Table 9: Use of induction (ATG or IL2 receptor blockers) in 3 groups was as follows: Group 1-15; in Group 2 - 35; in Group 3 - 17. Different induction protocols used in 3 groups.

Table 10: Use of anti-proliferatives (AZA: MMF) in 3 groups were as follows: in Group 1- 20:14; in Group 2 - 50:62 and in Group 3 - 11:22.

Complications

Biopsy proven CNI toxicity in 3 groups was as follows: Group 1 - 2 (5.9%); in Group 2-9 (8.03%) and in Group 3 - 5 (15.1%). Table 11 shows its distribution in 3 groups.

Table 11: Biopsy proven CNI toxicity in 3 groups was as follows: Group 1-2 (5.9%); in Group 2 - 9 (8.03%) and in Group 3 - 5 (15.1%). Table 11 shows its distribution in 3 groups.

Rejections

Over the course of one year following transplant, there were 44 (24.58%) cases of biopsy proven ACR. When examined by quartile, a significant reduction in the rates of ACR was seen from Groups 1- 3. In Group 1 total ACR were 12 (35.3%); in Group 2 total ACR were 27(24.1%); and in Group 3 total ACR were 5(15.2%). This is shown in Tables 12-15.

Table 12: New onset diabetes after transplant (NODAT) in 3 groups was as follows: Group 1- 17(50%); Group 2 - 42 (13.5%) and in Group 3 -14 (42.4%).

Table 13: Non-infectious complications occurring during hospitalization and outpatient follow-up were as follows: Femoral neuropathy - 2; G.I side effects of MMF - 3; Hypertensive encephalopathy - 1; Proteinuria - 1; TMA -1; TRAS - 2.

Table 14: Infectious complications were present in 57 patients .They were as follows: Acute gastroenteritis-5; CMV disease -14; Urinary tract infection - 26; Tuberculosis -2; Lower respiratory tract infection- 3; Herpes Zoster- 1; Post transplant HCV-1; post transplant HBV-3; Infected lymphocoel -1; Polyoma virus infection -1. Table 14 shows this distribution.

Table 15: In Group 1 total ACR were 12 (35.3%); in Group 2 total ACR were 27(24.1%); and in Group 3 total ACR were 5(15.2%). This is shown in table 15.

Discussion

ACR is a major factor in determining long-term graft outcome and its occurrence is heavily weighted towards the immediate posttransplant period. The critical influence of maintaining adequate early levels of immunosuppressive medications has been previously emphasized. Perico et al found that cylosporin levels on day 2 posttransplant were highly predictive of ACR episodes. Similarly, El- Sabrout et al. describe a significant reduction in ACR rates without an increase in toxicity after a loading dose of sirolimus. Staatz et al. identified a strong relationship between median TAC in the first post-transplant month and ACR. Their data were further analyzed by stratification into three groups based on median TAC, and those with the highest (10-15 ng/dl) values experienced no episodes of ACR. We found that biopsy proven ACR were reduced in a linear, graded fashion at all time points and for all TAC increments (Tables 16-25).

Table 16: Banff grading of these rejection episodes showed that grade 2 and grade 3 rejection were absent in Group 3, as seen clearly in table 16.

Table 17: Rates of post transplant infections in each group were as follows: in Group1- 12 (35.3%); in Group 2 - 33(29.5%) and in Group 3 - 15(45.4%). This is seen in table 17.

Table 18: Graft survival rates at the end of 1 year in each group was as follows: in Group 1 - 97.1%; in Group 2-98.2% and in Group 3 - 100% as shown in table 18.

Table 19:

Table 20:

Table 21:

Table 22:

Table 23:

Table 24:

Table 25:

Our results suggest that targeting baseline (pretransplant) trough (T0) tacrolimus levels similar to those seen in Group 3(>15ng/ml) immediately post-transplant can yield extremely low ACR rates in the long term. With higher trough levels severity of rejections (based on Banff classification) also reduces and we did not encounter any antibody mediated or severe TIR rejection when the baseline trough levels were more than 15ng/dl. Tacrolimus toxicity like NOD was not different among various trough level groups, though there was a trend towards higher nephrotoxicity with higher baseline trough levels. Thus we propose that a target baseline trough tacrolimus levels similar to that seen in Group 3 would achieve the optimal balance between efficacy and toxicity. To avoid toxicity, the TAC dose was promptly adjusted to achieve a target range of 10-15 ng/ml before the end of first post transplant week. Despite this, a tendency towards increased toxicity was observed and warrants discussion. Despite a slower fall to nadir creatinine with higher baseline trough tacrolimus level, differences were undetectable by the end of the first week post-transplant. As mentioned earlier, in our study there was no trend towards increased NODAT in patients with higher baseline trough tacrolimus levels (Tables 17-35).

Table 26:

Table 27:

Table 28:

Table 29:

Table 30:

Table 31:

Table 32:

Table 33:

Table 34:

Table 35:

The potential for TAC to induce this complication is well known, although it is unclear if this is a dose-related phenomenon. Two recent studies were unable to demonstrate an association between Tacrolimus trough levels and the development of NODAT at any time point out to five years post-transplant. However, in an earlier study of 76 patients, Rodrigo et al. found that Tacrolimus trough levels of >24ng/ml early post-transplant was an independent risk factor for the development of NODAT. Although, all the patients in the study were started with initial dose of tacrolimus of 0.15mg/kg, only 18% could achieve the trough level of >15ng/ml.That an initial dose of 0.15mg/kg should yield such a wide range of early tacrolimus level is testament to the variability in tacrolimus handling in humans. To implement the finding of this study into clinical practice, knowledge of an individual's response to the drug before they are transplanted would be useful (Tables 36-44).

Table 36:

Table 37:

Table 38:

Table 39:

Table 40:

Table 41:

Table 42:

Table 43:

Table 44:

This question is being addressed by an Australian study that is soon to be reported. Increasing recipient age does appear to affect tacrolimus pharmacokinetics in both children and adults, with higher tacrolimus seen in older patients despite equivalent dosing. This suggests that younger patients would benefit from a higher initial tacrolimus dose, targeting tacrolimus similar to those observed in Group 3(.15ng/ml). This study demonstrates a clear association between baseline (pre-transplant) trough tacrolimus level and reduced long term ACR rates. Targeting high baseline tacrolimus levels (>15ng/ml) and aggressively managing tacrolimus dosing in this critical period of antigen presentation and immunological activation may result in reduced rates of long-term allograft damage (Tables 44-50).

Table 45:

Table 46:

Table 47:

Table 48:

Table 49:

Table 50:

Conclusion

In summary, our study shows that the incidence of early rejection reduces as the baseline (pre-transplant) trough tacrolimus level increases. It also shows that with higher trough level severity of rejection also reduces and that there was no severe TIR and antibody mediated rejection when trough level was > 15ng/ml. Our study also showed that the incidence of NODAT was not different among various trough levels; although there was a trend towards higher rate of biopsy proven nephrotoxicity with higher trough levels. It was also seen that only 18% of the patients could achieve a baseline trough level of >15ng/ml inspite of being started on same doses of tacrolimus (0.15mg/kg) pretransplant .This shows a wide variability in tacrolimus handling in humans.

To conclude,

a. Incidences of early rejection reduces as the pretransplant trough tacrolimus level increases.

b. With higher trough level severity of rejection also reduces and we did not encounter any severe.

c. TIR or antibody mediated rejection when trough level was > 15 ng/ml.

d. NOD was not different among various trough levels and trend towards higher nephrotoxicity with higher trough levels.

e. Only 18 % could achieve the trough level of > 15 ng/ml.

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