Effect of interferon-alpha treatment in hemodialysis patients and renal transplant recipients with chronic hepatitis C

Hepatitis C Virus Infection in Patients with End-Stage Renal Disease: A Study from a Tertiary Care Centre in India

BACKGROUND

Hepatitis C Virus (HCV) infection is common in patients with end stage renal disease (ESRD) and is an important cause of liver disease. We describe the demographic, clinical and biochemical profile of these patients from a tertiary care center of north India.

METHODS

Records of consecutive patients of HCV infection with ESRD on maintenance hemodialysis or with renal transplantation who presented to our unit from January 2009 to June 2013 were analyzed. The diagnosis of HCV was based on HCV-RNA positivity and/or positive anti-HCV serology. Those with positive anti-HCV serology and negative HCV-RNA on two occasions at 3-month interval, without treatment with interferon, were excluded.

RESULTS

140 patients (median age 44 years [range 18-68], 69% males) were included. Six patients had co-infections (HBV 5, HIV 1). Most (99, 71%) patients were asymptomatic for liver disease and HCV was identified either on routine screening (39, 28%) or during investigation for raised liver enzymes (60, 43%). Remaining 41 (29%) were symptomatic for liver disease, either in the form of jaundice alone (14, 10%), or decompensated liver disease (27, 19%). Median time between initiation of hemodialysis and HCV detection was 33 (range 0-124) months. Thirty-four (27%) patients had received renal transplantation. In 11 patients HCV was detected after renal transplantation. In 23 (18%) patients anti-HCV was falsely negative but HCV-RNA was positive. Nearly 35% patients had concomitant diabetes. Median Bilirubin, AST, and ALT were 1.1 mg/dL, 42 IU/L and 44 IU/L, respectively. HCV-RNA was more than 5 log in 49/88(59%) patients. Median HCV-RNA was 6.5 × 10(5) IU/ml (Range 650 to >10 million IU/ml). Genotype-1 was the commonest genotype (30/56, 54%) followed by genotype-3 (17/56, 30%).

CONCLUSION

HCV infection is usually asymptomatic in patients with ESRD, however, it may lead to jaundice and decompensated liver disease. False negative anti-HCV is quite common. We found that genotype-1 was commoner than genotype-3 in our cohort of ESRD patients. Most of the patients have high viral load.

Treatment of hepatitis C after kidney transplant: a pooled analysis of observational studies

Various authors have given IFN-based therapy for hepatitis C among renal transplant recipients but the efficacy and safety of this approach remains unclear. A systematic review of the literature with a meta-analysis of clinical studies was performed in order to assess efficacy and safety of antiviral therapy (IFN-based therapy) in renal transplant recipients with hepatitis C virus infection. The primary outcomes were sustained virological response (as a measure of efficacy) and/or drop-out rate (as a measure of tolerability). The random-effects model of DerSimonian and Laird was used, with heterogeneity and sensitivity analyses. Sixteen studies (187 unique patients) were identified, one being controlled study. The summary estimate for sustained virological response and dropout rate was 0.34 (95% confidence intervals: 0.27, 0.42) and 0.32 (95% CI: 0.21, 0.44), respectively. The studies were heterogeneous with regard to dropout rate but not to sustained viral response. The most common side-effect requiring interruption of treatment was graft dysfunction (n = 27; 51%). Stratified analysis reported a higher rate of drop-outs in those studies based on IFN monotherapy (pooled event rate, 0.43; 95% CI: 0.25, 0.63). Meta-regression analysis showed an inverse relationship between reference year (P = 0.019), length of IFN therapy (P = 0.029) and drop-out rate. IFN-based therapy has inadequate safety and tolerance after renal transplantation. The reasons for the high rate of graft dysfunction after IFN have not been fully elucidated. Antiviral treatment of hepatitis C among kidney graft recipients continues to be a challenge to transplant physicians.

Treatment of hepatitis C virus infection in patients on maintenance hemodialysis: a single United Arab Emirates center experience

BACKGROUND

Hepatitis C is prevalent among hemodialysis patients. In patients with normal kidney function, treatment with pegylated interferon and ribavirin can lead to eradication of HCV (hepatitis C virus). But the treatment is more problematic in patients with impaired kidney function, in part due to the altered pharmacokinetics of these medications. Despite recent guidelines, the optimal strategy in this group of patients is not well defined.

METHOD

In a retrospective study, we reviewed all patients with chronic hepatitis C on hemodialysis treated at Sheikh Khalifa Medical City, in the United Arab Emirates between 2003 and 2009. The aim of our study was to determine the rate of sustained viral response (SVR) and to establish the safety and rate of dropouts in the different treatment regimens used (patients treated with peginterferon only and patients treated with peginterferon and low dose ribavirin).

RESULTS

22 patients were treated during this period. 5 patients received monotherapy with a reduced dose of peginterferon alfa 2b s.c. once weekly while 17 patients were treated with a combination of reduced dose of peginterferon alfa 2a or 2b s.c. once weekly and a low dose ribavirin (200mg/day). A SVR was achieved in 73% (16/22 patients) of the total patient population and in 76% (13/17 patients) in the sub-group of patients treated with a combination therapy. The tolerability was high. No patients had to discontinue their treatment. The use of ESA (erythropoietin stimulating agents) and G-CSF was common in the combination therapy (94% and 53% respectively).

CONCLUSION

In our study of patients on hemodialysis with chronic hepatitis C, the use of peginterferon or a combination of peginterferon with a low daily dose of ribavirin achieved a high rate of SVR and the rate of dropout was low after pursuing an aggressive management of side effects.

Hepatitis C and kidney disease

Multiple extrahepatic manifestations have been associated with chronic hepatitis C, the most important among them being cryoglobulinemia, glomerulonephritis, porphyria cutanea tarda, lichen planus, seronegative arthritis, and lymphoproliferative disorders as in the sudies of Bonkovsky and Mehta (2001) and El-Serag et al. (2002). We will discuss in this paper chronic hepatitis C- related kidney disease and course and management of patients with chronic hepatitis C in special circumstances like hemodialysis and kidney transplantation.

Pegylated interferon-alpha-based treatment for chronic hepatitis C in renal transplant recipients: an open pilot study

Treatment of hepatitis C in renal transplant recipients remains a controversial issue, as interferon therapy has been associated with a high risk of rejection and poor efficacy. We report here the use of pegylated interferon-alpha, alone or in combination with ribavirin, in renal transplant recipients with chronic hepatitis C. Eight renal transplant recipients with chronic hepatitis C were recruited. The mean delay between renal transplantation and antiviral therapy was 198.8 months. Sustained virological response was observed in four of out eight patients. Three patients with sustained virological response were genotype 2, one was genotype 1; fibrosis stages were F1 for one patient, F2 for 2, F3 for one. At baseline, renal dysfunction was moderate in seven patients and severe in one patient. No patient experienced rejection episodes during or after pegylated interferon-alpha therapy. One patient developed haemolytic uraemic syndrome, which eventually resulted in graft loss and return to dialysis. In conclusion, for renal transplant recipients treated with pegylated interferon-alpha-based therapy, we observed a low risk of renal dysfunction, acceptable tolerance and significant virological efficacy. This is therefore the first study to suggest that pegylated interferon-alpha could be proposed late after transplantation to renal transplant recipients.

Hepatitis C and renal transplantation: a review on historical aspects and current issues

Chronic liver disease has a significant impact on the survival of renal transplant recipients with an incidence rate of 4-38%. Approximately, 8-28% of renal transplant recipients die due to chronic liver disease. Hepatitis C seems to be the leading cause of chronic liver disease in kidney recipients. Hepatitis C virus (HCV) infection has a wide range of prevalence (2.6-66%) among renal transplant recipients living in different countries with great genotype diversity in different parts of the world. Nowadays, antiviral drugs are used for the management of hepatitis C. Because of graft-threatening effects of some antiviral drugs used in HCV-infected renal transplant recipients, we specifically focused on HCV treatment after renal transplantation. Treatment of post-renal transplantation chronic liver disease with INF and ribavirin remains controversial. Anecdotal reports on post-renal transplantation hepatitis C demonstrate encouraging findings. This review summarises the most current information on diagnosis, treatment, prognosis, complications as well as the new aspects of treatment in HCV-infected renal transplant recipients. HCV belongs to the family of Flaviviridae, genus Hepacivirus.

Treatment of chronic hepatitis C in hemodialysis patients

Hepatitis C virus (HCV) infection is especially problematic in patients with end-stage renal disease (ESRD) who are undergoing hemodialysis. Rates of HCV infection are higher among hemodialysis patients than in the general population, and several routes of transmission are thought to stem from the dialysis unit. Management of chronic hepatitis C is also more complicated in hemodialysis patients because of altered pharmacokinetics and a predisposition for drug-related toxicity, particularly ribavirin-induced anemia. Clinical trials of patients with chronic hepatitis C and healthy, functioning kidney grafts are rare because of the inherent dangers of graft rejection. As a result, most studies in patients with ESRD have focused on patients waiting for a kidney transplant. Additionally, because ribavirin is contraindicated in this patient population, many studies have examined monotherapy treatments. According to meta-analyses, conventional interferon alfa treatment yields a sustained virological response (SVR) rate of 37%, whereas studies of pegylated interferon alfa monotherapy have yielded SVR rates between 13% and 75%. Several small studies have also used the monitoring of ribavirin plasma concentrations or hemoglobin levels to facilitate the use of combination therapy. In light of the results from these clinical trials, we herein review treatment guidelines and recommend strategies to help optimize the treatment of patients with ESRD.

CONCLUSION

There remains a lack of clarity surrounding the most effective treatment options for patients with chronic hepatitis C and ESRD. Treatment can be effective with many patients attaining SVR; however, unfavorable tolerability with interferon alfa-based therapy remains a concern and thus close supportive care should be aggressively pursued to help maintain adherence.

HCV in patients with end-stage renal disease

Chronic hepatitis C virus (HCV) infection remains an important cause of liver disease in patients with end-stage renal disease (ESRD) and conversely, renal failure has a significant impact on morbidity and mortality throughout the natural history of chronic HCV and its treatment. With improved awareness within dialysis units of the potential for spread and the institution of preventative measures, the prevalence of HCV infection in the hemodialysis-dependent population has continued to decline since 1995. Use of HCV (+) donor kidneys is associated with an increase in the prevalence of liver disease, but when compared with continued hemodialysis, transplantation using these kidneys is associated with improved survival. Overall, survival in patients with chronic HCV infection appears to be better after renal transplantation when compared with maintenance hemodialysis, and transplant should be considered for these patients. Data support the use of interferon and the improved efficacy of pegylated interferon formulations for treatment of chronic HCV infection in ESRD patients, although tolerability continues to be troublesome. The newest and most promising data regarding the treatment of HCV in ESRD involve the combination of reduced dose ribavirin with interferon or pegylated interferon suggesting similar enhancements in sustained virologic response (SVR) as seen in non-ESRD patients, but caution is advised, as all studies to date used ribavirin plasma concentration monitoring in patient with ESRD. Finally, with regard to postrenal transplant treatment of HCV infection, there is no evidence to support treatment with interferon-based therapy and pretransplant treatment remains the best option whenever possible.

Meta-analysis: anti-viral therapy of hepatitis C virus-related liver disease in renal transplant patients

BACKGROUND

The efficacy and safety of interferon-based therapy in renal transplant recipients with hepatitis C remains unclear, although a number of small clinical trials have been published addressing this issue.

AIM

To evaluate efficacy and safety of antiviral therapy with interferon (interferon alone or interferon plus ribavirin) in renal transplant patients with hepatitis C by performing a systematic review of the literature with a meta-analysis of clinical trials.

METHODS

The primary outcomes were sustained virological response (as a measure of efficacy) and/or drop-out rate (as a measure of tolerability). We used the random-effects model of DerSimonian and Laird, with heterogeneity and sensitivity analysis.

RESULTS

We identified 12 clinical trials (102 unique patients); there was one controlled study. The summary estimate for sustained virological response and drop-out rate was 18.0% (95% CI 7.0-29.0%) and 35.0% (95% CI 20-50%), respectively. The most frequent side-effect requiring interruption of treatment was graft dysfunction (n = 28; 71.7%). Meta-regression analysis showed an inverse and significant association between reference year and drop-out logit rate (P = 0.012); an inverse link between sustained virological response logit rate and frequency of hepatitis C virus genotype 1 (P = 0.067) and cirrhosis (P = 0.08) was found, even if no statistical significance was reached. No publication bias was observed.

CONCLUSIONS

Interferon-based therapy of hepatitis C has poor tolerance and safety after renal transplant. The optimal treatment of hepatitis C after renal transplant requires additional agents or alternative therapeutic approaches.

Hepatitis C eradication and improvement of cryoglobulinemia-associated rash and membranoproliferative glomerulonephritis with interferon and ribavirin after kidney transplantation

Postrenal transplant hepatitis C is increasing in frequency due to the high prevalence of hepatitis C among patients with renal failure. Despite this, there is still no standard hepatitis C treatment available for renal transplanted recipients. Combination antiviral hepatitis C therapy, the standard of care in the nontransplant population, is generally avoided because of documented renal graft rejection secondary to interferon treatment. A case of a male patient with postrenal transplant hepatitis C, which was associated with cryoglobulinemia and glomerulonephritis of the graft, is presented. He was treated with standard interferon with ribavirin. Sustained viral clearance was achieved despite ongoing evidence of cryoglobulinemia. Renal function, which had been deteriorating before treatment, improved as evidenced by the stabilization of serum creatinine and marked improvement of proteinuria. In conclusion, in selected patients, combination antiviral therapy may still be a viable option postrenal transplant.

Treatment of hepatitis C in potential kidney and heart transplant patients

Hepatitis C virus (HCV) is common in certain solid organ transplant recipients, most notably in those undergoing liver or kidney transplantation. Infection typically antedates transplantation but may have been acquired at the time of transplantation via infected blood products or organs. A more rapid and aggressive course of HCV-related infection and liver disease is the major concern in organ transplant recipients compared with immunocompetent patients. HCV-related liver disease is an important cause of morbidity and mortality in patients with end-stage renal disease treated by dialysis or transplantation. The outcome of HCV infection in renal and liver transplant recipients has been extensively investigated, whereas literature on HCV-related liver disease among patients with orthotopic heart transplantation is scanty. This article reviews the literature concerning the treatment of HCV-related liver disease in renal and orthotopic heart transplantation.

Renal transplant recipient with chronic hepatitis C who obtained sustained viral response after interferon-beta therapy

A 44-year-old Japanese woman with a history of living-related renal transplantation was treated with interferon-beta (IFN-beta) for chronic infection with sero-group 2 hepatitis C virus (HCV). Serum HCV-RNA titer was 160 kilo-international units/ml. Treatment with intravenous IFN-beta daily was given for 6 weeks. Serum HCV-RNA was undetectable at 3 weeks after initiating therapy. Renal graft rejection did not occur. Six months after completing therapy, she obtained sustained viral response. This case demonstrates that IFN-beta therapy safely induced clearance of HCV in a renal transplant recipient with stable renal function, low viral load and/or HCV sero-group 2.

Treatment of chronic viral hepatitis in patients with renal disease

In the last several years, numerous studies on the natural history and outcomes of viral hepatitis in dialysis and transplantation have been reported. Despite these, the management of hepatitis C virus or hepatitis B virus-related liver disease in end-stage renal disease continues to be an area of controversy. This article aims to address the current therapeutic options for patients with renal disease and chronic viral hepatitis.

Hepatitis C and renal disease: an update

Hepatitis C is both a cause and a complication of chronic renal disease. Chronic infection with hepatitis C virus (HCV) can lead to the immune complex syndromes of cryoglobulinemia and membranoproliferative glomerulonephritis (MPGN). The pathogenetic mechanisms for these conditions have not been defined, although they are clearly caused by the chronic viral infection. Management of HCV-related cryoglobulinemia and MPGN is difficult; antiviral therapy is effective in clearing HCV infection in a proportion of patients, but these conditions can be severe and resistant to antiviral therapy. Hepatitis C also is a complicating factor among patients with end-stage renal disease and renal transplants. The source of HCV infection in these patients can be nosocomial. Screening and careful attention to infection control precautions are mandatory for dialysis units to prevent the spread of hepatitis C. Prevention of spread is particularly important in these patients because HCV infection is associated with significant worsening of survival on dialysis therapy, as well as after kidney transplantation. Furthermore, therapy for hepatitis C is problematic, only partially effective, and associated with significant side effects in this population. There are significant needs in both basic and clinical research in the pathogenesis, natural history, prevention, and therapy for hepatitis C in patients with renal disease.

Meta-analysis: interferon for the treatment of chronic hepatitis C in dialysis patients

BACKGROUND

The efficacy of interferon monotherapy in dialysis patients with chronic hepatitis C remains unclear, although a number of small clinical trials have been published addressing this issue.

METHODS AND AIMS

We evaluated the efficacy and safety of initial interferon monotherapy in dialysis patients with chronic hepatitis C by performing a systematic review of the literature with a meta-analysis of clinical trials. The primary outcome was sustained virological response (as a measure of efficacy); the secondary outcome was drop-out rate (as a measure of tolerability). We used the random effects model of Der Simonian and Laird, with heterogeneity and sensitivity analyses.

RESULTS

We have identified 14 clinical trials (269 unique patients); two were controlled studies. The mean overall estimate for sustained virological response (SVR) and drop-out rate was 37%[95% confidence interval (CI) 28-48] and 17% (95% CI 10-28), respectively. The most frequent side-effects requiring interruption of treatment were flu-like symptoms (17%), neurological (21%) and gastrointestinal (18%). The overall weighted estimate for SVR in patients with hepatitis C virus genotype 1 was 30.6% (95% CI 20.9-48). In the sub-group of clinical trials (n = 5) with standard interferon administration (3 million units [MUI] thrice weekly, subcutaneous route, 24-week treatment), the overall mean estimate of SVR was 39% (95% CI 25-56). The studies were heterogeneous with regard to SVR and drop-out rate.

CONCLUSIONS

Tolerance to initial interferon monotherapy was lower in dialysis than nonuremic patients with chronic hepatitis C. However, more than one-third of haemodialysis patients with chronic hepatitis C have been successfully treated with interferon. Longer duration of interferon monotherapy does not appear to have a beneficial effect on the response rate. Further studies are warranted to define the optimal anti-viral regimen for chronic hepatitis C in dialysis population.

Chronic liver disease in kidney recipients with hepatitis C virus infection

BACKGROUND

The prevalence of anti-hepatitis C virus (HCV) positive test is higher among patients in dialysis and in kidney recipients than in general population. Hepatitis C virus infection is the main cause of chronic liver disease in renal transplant patients. Liver biopsy and virological analysis were performed to clarify the grade of liver damage in kidney recipients.

METHODS

Renal recipients patients with at least 5 yr under immunosuppression were submitted to clinical and laboratory analysis. Patients who tested anti-HCV positive were candidates to liver biopsy with no regard to transaminase levels.

RESULTS

Forty-five patients tested anti-HCV positive and 42 anti-HCV negative. Twenty-six anti-HCV and RNA-HCV positive patients were submitted to liver biopsy. Seventy-three percentage of these patients presented chronic active hepatitis, from these only one patient presented cirrhosis. Only 29% of the anti-HCV positive group presented elevated alanine aminotransferase levels. Anti-HCV positive patients presented longer previous time on dialysis and less rejection episodes than the group anti-HCV negative (p < 0.05). All anti-HCV positive patients but one tested RNA-HCV positive by polymerase chain reaction (PCR).

CONCLUSIONS

In this series the prevalence of anti-HCV positive is 51.7%. Most of the patients presented liver damage in histology caused by HCV. However, we found only mild or minimal fibrosis and inflammatory activity grade, despite 10 yr of HCV infection and 5 yr of immunosuppressive treatment. Only one patient presented cirrhosis (4%). Performing serial liver biopsies in a long-term follow-up is needed to clarify the impact of HCV infection in renal transplant patients.

Management of chronic viral hepatitis before and after renal transplantation

Hepatitis C virus (HCV) infection is present in 2-50% of renal transplant recipients and patients receiving hemodialysis. Renal transplantation confers an overall survival benefit in HCV positive (HCV+) hemodialysis patients, with similar 5-year patient and graft survival to those without HCV infection. However, longer-term studies have reported increased liver-related mortality in HCV-infected recipients. Unfortunately, attempts to eradicate HCV infection before transplant have been disappointing. Interferon is poorly tolerated in-patients with end-stage renal disease and ribavirin is contraindicated because reduced renal clearance results in severe hemolysis. Antiviral therapy following renal transplantation is also poorly tolerated, because of interferon-induced rejection and graft loss. Although the prevalence of hepatitis B virus (HBV) infection has declined in hemodialysis patients and renal transplant recipients since the introduction of routine vaccination and other infection control measures, it remains high within countries with endemic HBV infection (especially Asia-Pacific and Africa). Renal transplantation is associated with reduced survival in HBsAg+ hemodialysis patients. Unlike interferon, lamivudine is a safe and effective antiviral HBV treatment both before and after renal transplantation. Lamivudine therapy commenced at transplantation should prevent early posttransplant reactivation and subsequent progression to cirrhosis and late liver failure. This preemptive therapy should also eradicate early liver failure from fibrosing cholestatic hepatitis. Because cessation of treatment may lead to severe lamivudine-withdrawal hepatitis, most patients require long-term therapy. The development of lamivudine-resistance will be accelerated by immunosuppression and may result in severe hepatitis flares with decompensation. Regular monitoring with liver function tests and HBV DNA measurements should enable early detection and rescue with adefovir. Chronic HCV and HBV infections are important causes of morbidity and mortality in renal transplant recipients. The best predictor for liver mortality is advanced liver disease at the time of transplant, and liver biopsy should be considered in all potential HBsAg+ or HCV+ renal transplant candidates without clinical or radiologic evidence of cirrhosis. Established cirrhosis with active viral infection should be considered a relative contraindication to isolated renal transplantation.

Hepatitis C virus seropositivity at the time of renal transplantation in the United States: associated factors and patient survival

National statistics for patient characteristics and survival of renal transplant recipients positive for hepatitis C virus (HCV+) at the time of renal transplant are presented. A historical cohort analysis of 33479 renal transplant recipients in the United States Renal Data System from 1 July, 1994 to 30 June, 1997 has been carried out. The medical evidence form was also used for additional variables, but because of fewer available values, this was analyzed in a separate model. Outcomes were patient characteristics and survival associated with HCV+. Of 28692 recipients with valid HCV serologies, 1624 were HCV+ at transplant (5.7% prevalence). In logistic regression analysis, HCV+ was associated with African-American race, male gender, cadaveric donor type, increased duration of pre-transplant dialysis, previous transplant, donor HCV+, recipient (but not donor) age, serum albumin, alcohol use, and increased all-cause hospitalizations. Diabetes and IgA nephropathy were less associated with HCV+. Total all-cause, unadjusted mortality was 13.1% in HCV+ vs. 8.5% in HCV- patients (p <0.01 by log rank test). In Cox regression, mortality was higher for HCV+ (adjusted hazard ratio = 1.23, 95% confidence interval = 1.01-1.49, p = 0.04). HCV+ recipients were more likely to be African-American, male, older, and to have received repeat transplants and donor HCV+ transplants. HCV+ recipients also had substantially longer waiting times for transplant. In contrast to recent studies, diabetes did not have an increased association with HCV+, perhaps due to limitations of the database. HCV+ recipients had increased mortality and hospitalization rates compared with other transplant recipients.

Hepatitis C virus infection and renal transplantation

With the success of organ transplantation, liver disease has emerged as an important cause of morbidity and mortality of renal transplant (RT) recipients. Numerous studies performed during the 1990s have shown that hepatitis C virus (HCV) infection is the leading cause of chronic liver disease among RT recipients. The transmission of HCV by renal transplantation of a kidney from an HCV-infected organ donor has been shown unequivocally. Liver biopsy is essential in the evaluation of liver disease of RT recipients, and histological studies have shown that HCV-related liver disease after renal transplantation is progressive. The outcome of HCV-related liver disease is probably more aggressive in RT recipients than immunocompetent individuals. Various factors can affect the progression of HCV in the RT population: coinfection with hepatitis B virus, time of HCV acquisition, type of immunosuppressive treatment, and concomitant alcohol abuse. The role of virological features of HCV remains unclear. The natural history of HCV infection after renal transplantation is under evaluation; however, recent surveys with long follow-ups have documented adverse effects of HCV infection on patient and graft survival in RT recipients. Use of renal grafts from HCV-infected donors in recipients with HCV infection does not appear to result in a greater burden of liver disease, at least for a short period. The association between HCV and de novo or recurrent glomerulonephritis after RT has been hypothesized and is an area of avid research. Reported studies do not support interferon (IFN) treatment for RT recipients with chronic hepatitis C because of the frequent occurrence of graft failure, and information on the use of other types of IFN or combined therapy (IFN plus ribavirin or amantadine) is not yet available in the RT population.