|Autogenous versus prosthetic vascular access for hemodialysis: a systematic review and meta-analysis
|Murad MH, Elamin MB, Sidawy AN, Malaga G, Rizvi AZ, Flynn DN, Casey ET, McCausland FR, McGrath MM, Vo DH, El-Zoghby Z, Duncan AA, Tracz MJ, Erwin PJ, Montori VM
The review concluded that low-quality evidence from inconsistent studies with limited protection against bias showed that autogenous access for chronic haemodialysis was superior to prosthetic access. The authors' cautious conclusions are likely to be reliable.
To compare the effectiveness of autogenous arteriovenous access with prosthetic access for chronic haemodialysis in terms of patient-important outcomes.
MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL), SCOPUS and Web of Science were searched to March 2007; search terms were not reported. Further studies were sought from experts, reference lists of included studies and ISI Science Citation Index. There were no language restrictions.
Randomised controlled trials (RCTs) and cohort studies that compared patients who had autogenous access with a concurrent group who had prosthetic access were eligible for inclusion. Outcomes of interest were death, access infection, postoperative complications, duration of hospitalisation due to access complications and patency.
Most studies were of incidental dialysis patients; the remaining studies looked at prevalent dialysis patients, or a mixed population. Mean age of included patients was 55 years (range nine to 78 years). The most common locations of access were forearm and upper arm; a small number of studies used the elbow, wrist, thigh, shoulder, neck and chest.
Two reviewers independently assessed studies for inclusion. Disagreements were resolved through consensus or arbitration.
Assessment of study quality
Study quality of observational studies was assessed using the Newcastle-Ottowa scale. Allocation concealment and blinding were assessed for RCTs. It appeared that two reviewers independently assessed study quality.
Two reviewers independently extracted data to calculate relative risks (RRs) or mean differences and 95% confidence intervals (CI) for each outcome. Patency rates were converted to dichotomous outcomes for specific time periods (12 and 36 months). Authors were contacted for any missing or unreported data.
Methods of synthesis
Meta-analyses of pooled relative risks or weighted mean differences were performed using a random-effects model. Heterogeneity was assessed using the I2 statistic. Subgroup analyses investigated the effect of factors such as age, gender, diabetes status, presence of peripheral vascular disease, location of access, reporting of outcomes by patient or access and whether patients were incidental or prevalent haemodialysis patients. Meta-regression was conducted to assess the effect of study quality and duration of follow-up on patency. Sensitivity analyses were conducted.
Results of the review
Eighty-three studies were included in the review (n=69,600, range 30 to 25,226 participants). Three studies were open RCTs and 80 were observational cohort studies (56 retrospective and 24 prospective).Mean sample size was 850 patients. Mean duration of follow up was 2.8 years.
For the observational studies, only 46% controlled for at least one possible confounder in cohort selection or analysis. Only a fifth of studies had losses to follow up of less than 10%. Allocation was concealed and data collectors blinded in one of the RCTs.
Autogenous access was associated with a significantly reduced risk of death (RR 0.76, 95% CI 0.67 to 0.86, I2=48%; 27 studies) and access infection (RR 0.18, 95% CI 0.11 to 0.31, I2=93%; 43 studies) compared to prosthetic access. Primary and secondary patency rates were significantly higher (at 12 and 36 months) in patients with autogenous access. Autogenous access was also associated with a nonsignificant reduction in risk of postoperative complications of access placement other than infection (31 studies) and length of hospital stay resulting from such complications (three studies).
Subgroup analyses found that the magnitude of benefit from autogenous access (compared to prosthetic access) was significantly greater when autogenous access was placed in the lower arm. There were no significant differences with respect to patient type (incidental or prevalent haemodialysis). Meta-regression showed that neither study quality nor duration of follow up explained between-study variability in patency.
Further results were reported.
Low-quality evidence from inconsistent studies with limited protection against bias showed that autogenous access for chronic haemodialysis was superior to prosthetic access.
The review addressed a clear question and was supported by appropriate inclusion criteria. Attempts to identify relevant studies in any language were undertaken by searching electronic databases, checking references and contacting experts. Although search terms were not reported, the authors stated that an expert reference librarian carried out the search. It was unclear whether the authors made efforts to minimise the risk of publication bias by looking for and including unpublished studies. Suitable methods were employed to reduce the risks of reviewer error and bias for all relevant review processes. Study quality was assessed and was used in interpreting the results of the review (but only limited information was provided about the RCTs). Sufficient study details were provided. Although the authors pooled heterogeneous data using meta-analysis they recognised that the pooled results were of minimal clinical significance considering the low quality of the studies and the heterogeneity seen. Levels of statistical heterogeneity were reported for only a small number of the many analyses conducted. Cut-off points for study quality and duration of follow-up were not defined for the meta-regression. More details about the RCTs and analyses just for RCTs would have been informative, but were not reported. Although the review had a few limitations, the authors' conclusions were suitably cautious in reflecting the limited evidence available and are likely to be reliable.
Implications of the review for practice and research
Practice: See implications for research (below).
Research: The authors stated that large randomised trials that measured patient-important outcomes were necessary to make recommendations with confidence.
The authors stated that one author obtained funding (no further details given).
Murad MH, Elamin MB, Sidawy AN, Malaga G, Rizvi AZ, Flynn DN, Casey ET, McCausland FR, McGrath MM, Vo DH, El-Zoghby Z, Duncan AA, Tracz MJ, Erwin PJ, Montori VM. Autogenous versus prosthetic vascular access for hemodialysis: a systematic review and meta-analysis. Journal of Vascular Surgery 2008; 48(5 Supplement): 34S-47S
Subject indexing assigned by NLM
Arteriovenous Shunt, Surgical /instrumentation; Blood Vessel Prosthesis; Humans; Renal Dialysis /methods; Transplantation, Autologous
Database entry date
This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.