***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Background . There is scarce information regarding the role of hepatitis C virus ( HCV ) infection in the development of infectious complications after kidney transplantation ( KT ) . Methods . We prospect ively analyzed all KT recipients included in the Spanish Network for the Research of Infection in Transplantation cohort from September 2003 to February 2005 with a posttransplant follow-up of 3 years and compared the incidence of both overall and specific infections according to the pretransplant anti-HCV antibody status . Results . Of 1302 analyzed recipients , 105 ( 8.1 % ) were anti-HCV positive . These patients presented a higher rate of previous transplant  ( P<0.001 ) , had a lower donor age ( P=0.055 ) , higher transfusion requirements ( P=0.037 ) , and more frequently received induction therapy with antithymocyte antibodies ( P=0.005 ) . We found no differences between anti-HCV-positive and -negative recipients in the overall incidence rate of infection ( 0.82 vs. 0.74 episodes per 1000 transplant-days , respectively ) . Nevertheless , anti-HCV-positive recipients had a higher cumulative incidence of bloodstream ( P=0.01 ) and upper urinary tract infections ( P=0.037 ) . Anti-HCV status emerged by logistic regression as an independent risk factor only for bloodstream infection ( odds ratio , 3.14 ; 95 % confidence interval , 1.19–8.24 ; P=0.020 ) . Anti-HCV-positive recipients also experimented a higher rate of recurrent acute rejection ( P=0.045 ) and retransplantation ( P=0.017 ) , with no differences in overall mortality . Conclusions . According to the results of the Spanish Network for the Research of Infection in Transplantation cohort , the incidence of some potentially severe posttransplant infections may be increased in anti-HCV-positive KT recipients BACKGROUND Traditional and largely qualitative review s of evidence are now giving way to much more structured systematic overviews that use a quantitative method to calculate the overall effect of treatment . The latter approach is dependent on the quality of primary studies , which may introduce bias if they are of poor method ologic quality . OBJECTIVE To test the hypothesis that the inclusion of poor- quality trials in meta-analyses would bias the conclusions and produce incorrect estimates of treatment effect . METHODS An overview of r and omized trials of antiestrogen therapy in subfertile men with oligospermia was performed to test the hypothesis . Data sources included online search ing of MEDLINE and Science Citation Index data bases between 1966 and 1994 , scanning the bibliography of known primary studies and review articles , and contacting experts in the field . After independent , blind assessment , nine of 149 originally identified studies met the inclusion criteria and were selected . We assessed study quality independently . Outcome data from each study were pooled and statistically summarized . RESULTS There was a marginal improvement in pregnancy rate with antiestrogen treatment ( odds ratio , 1.6 ; 95 % confidence interval , 0.9 to 2.6 ) . Sensitivity analyses on the basis of method ologic quality demonstrated that poor- quality studies produced a positive effect with treatment , whereas no benefit was observed with high- quality studies . CONCLUSION The results of a meta- analysis are influenced by the quality of the primary studies included . Method ologically , poor studies tend to exaggerate the overall estimate of treatment effect and may lead to incorrect inferences Hepatitis C virus ( HCV ) can be transmitted by transplantation of cadaver organs from donors with antibody to HCV ( anti-HCV ) ; therefore , transplantation of organs from anti-HCV positive donors to anti-HCV-negative recipients has been discouraged . We have looked at outcomes in recipients of organs from anti-HCV positive and negative donors to determine whether this advice is well-founded . Stored sera from 716 consecutive cadaver organ donors procured by the New Engl and Organ Bank between 1986 and 1990 were tested for anti-HCV by a first-generation ELISA ( ELISA1 ) ; 13 ( 1.8 % ) were positive . 29 recipients who received organs from these donors were the study group . 37 donors were r and omly selected from 703 ELISA1-negative cadaver organ donors . 74 recipients of organs from these 37 donors were the control group . Clinical records were review ed and recipient sera were tested for anti-HCV with a second-generation ELISA ( ELISA2 ) , and HCV RNA was tested for by polymerase chain reaction . Median post-transplant follow-up was 42 and 49 months for study and control groups . Post-transplantation prevalence of anti-HCV and HCV RNA was 67 % and 96 % among recipients from anti-HCV-positive donors , and 20 % and 18 % among recipients from anti-HCV-negative donors ( p < 0.001 ) . Post-transplantation non-A , non-B hepatitis , graft loss , and death were observed in 55 % , 52 % , and 31 % among recipients of organs from anti-HCV-positive donors , and 16 % , 53 % , and 33 % among recipients from anti-HCV-negative donors . In a proportional hazards model , the relative risks for non-A , non-B hepatitis , graft loss , and death among recipients from anti-HCV-positive donors were 4.37 ( 95 % CI 1.97 - 9.70 ) , 0.93 ( 0.51 - 1.70 ) , and 0.89 ( 0.41 - 1.93 ) . Transmission of HCV infection by organ transplantation increased the risk of liver disease among recipients . However , after 3.5 years , donor HCV infection did not adversely affect patient survival or graft survival Background . Hepatitis C virus ( HCV ) infection is common in kidney transplantation and is known to affect long-term patient and graft survival , as is time in renal-replacement therapy ( RRT ) . The aim of this study was to investigate HCV in relation to time in RRT and its impact on outcome after transplantation . Methods . A follow-up cohort study using Kaplan-Meier analysis and Cox proportional hazards model was performed in 545 kidney and 26 kidney-pancreas transplant recipients receiving transplants between 1989 and 1997 , with last follow-up on December 31 , 2002 . HCV status at transplantation and time in RRT were analyzed . Results . Time in RRT was significantly longer ( P<0.0001 ) , and previous transplantations were more common ( P=0.04 ) in the HCV-positive group . HCV significantly reduced patient ( P=0.0012 ) and graft survival ( P=0.0003 ) after transplantation . Adjustment for age , sex , diabetes , previous transplantations , type of transplant , and time in RRT result ed in a relative risk ( RR ) for death of 2.23 , 1.92 , and 1.07 for HCV , diabetes , and age , respectively . The RR for graft loss was 1.96 and 1.03 for HCV and age . Sex , previous transplants , and time in RRT did not affect HCV as an independent risk factor for patient or graft survival . The leading cause of death was cardiovascular disease in both groups . Conclusions . HCV was , in our series , more important than time in RRT for patient death and graft loss posttransplant . Successful pretransplant antiviral therapy could be more beneficial for HCV-infected patients rather than early transplantation for long-term outcome , but this needs to be studied prospect ively Controversy exists regarding the impact of pre-transplantation HCV infection on the outcome of renal transplantation . We compared the prevalence of post-transplantation liver disease and graft and patient survival among kidney transplant recipients with and without anti-HCV at the time of transplantation . Pre-transplantation sera from 103 r and omly selected recipients of kidneys from anti-HCV-negative donors were tested for anti-HCV using a second generation ELISA . Twenty-three ( 22 % ) were positive for anti-HCV and 80 ( 78 % ) were negative . Anti-HCV-positive recipients had a longer time on dialysis ( P=0.003 ) and had a higher number of previous transplants ( P=0.01 ) . Further , 61 % of anti-HCV-positive patients had a history of liver disease compared with 13 % of anti-HCV-negative patients ( P<0.001 ) . HCV RNA was detected in the pretransplantation serum in 61 % of anti-HCV positive recipients compared with 5 % of anti-HCV-negative recipients ( P<0.001 ) . Clinical follow-up on both anti-HCV-positive and -negative patients was obtained until December , 1993 . Median posttransplantation follow-up among recipients with anti-HCV prior to transplantation ( 45 months ) was shorter ( P=0.05 ) than that for recipients without anti-HCV ( 66 months ) . For recipients with anti-HCV prior to transplantation , the relative risk of posttransplantation liver disease was 5.0 ( 95 % confidence intervals of 2.4 to 10.5 ) ; the relative risk of graft loss was 1.3 ( 95 % confidence intervals of 0.6 to 2.6 ) ; the relative risk of death was 3.3 ( 95 % confidence intervals of 1.4 to 7.9 ) , and the relative risk of death due to sepsis was 9.9 ( 95 % confidence intervals of 2.6 to 38.3 ) . The results of this study demonstrate that pretransplantation HCV infection is associated with an increased risk of liver disease and death after renal transplantation . These results raise the question of whether anti-HCV-positive patients on dialysis should be offered renal transplantation as opposed to continuing dialysis 
    Output:
    
This meta- analysis of observational studies supports the notion that HCV-positive patients after RT have an increased risk of mortality and graft loss .