Results of these studies suggest that males, patients who have received immunosuppressant medications or red blood cell transfusion, those not exposed to antimicrobials, and those with neutropenia, malignancy, or liver disease may be at increased risk for bacteremia secondary to CAB. However, the weight and quality of evidence supporting the identified risk factors are weak. Despite an exhaustive search encompassing more than 30 years, we found only seven pertinent studies, and no single factor was identified by more than one study as producing an odds ratio or relative risk greater than 2 or less than 0.5. It has been suggested that associations identified in observational studies should be considered weak unless the relative risk is greater than 2 or the odds ratio is greater than 3 (Grimes & Schulz, 2012). In addition, the findings were heterogeneous. This may be due in part to the lack of consistency in definitions of bacteremia, the wide variety of risk factors examined across studies, and the inclusion of patients with and without catheters in different proportions across studies. Although all studies were subject to some degree of bias, findings from the case-control studies are likely the most credible.
Few of the identified risk factors are modifiable. Red blood cell transfusions can and should be limited, but it is likely that the benefits of transfusion or of immunosuppressant medications will outweigh the risk of bacteremic CAB in many cases. Catheter use is modifiable; clinicians can limit the use of urinary catheters in patients at high risk for bacteremia. Clinicians can expect to receive regular, reliable feedback of local incidence rates of bacteremia due to CAB from their hospital's infection control department. Guidelines for the prevention of catheter-associated urinary tract infections recommend internal reporting of bacteremia attributable to CAB, as well as rates of symptomatic catheter-associated urinary tract infection and proportion of appropriate urinary catheter use (Gould et al., 2010; Lo et al., 2008). Since 2009, the Centers for Disease Control and Prevention (CDC) has included criteria for asymptomatic bacteremic CAB in its surveillance definitions for the National Healthcare Safety Network (NHSN) (CDC, 2014).
Hospitals must report these rates for adult and pediatric ICUs through NHSN, in order to fulfill the Centers for Medicare and Medicaid Service's Hospital Inpatient Quality Reporting Requirements.
Future research into this question should focus on the role of diabetes and underlying urinary tract disease as risk factors, and should tease out the influence of urethral catheters independent of other urinary tract procedures or surgeries. Large case-control studies incorporating the risk factors identified in this review would help clarify the evidence base.
Findings of this review are supported by rigorous methods, including a medical librarian-assisted search, independent selection of studies by two reviewers using pre-determined inclusion criteria, and appraisal of potential for bias by two reviewers. In addition, our report adheres to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses: The PRISMA Statement. However, our review has several limitations. First, we did not include grey literature, such as conference proceedings, because the reports may be preliminary or may not be peer-reviewed. This exclusion of unpublished studies may have resulted in an overestimation of risks because studies with significant results are more likely to be published (Song, Eastwood, Gilbody, Duley, & Sutton, 2000). Second, our inclusion of only English language studies may also have resulted in overestimation of risks because studies conducted in non-English-speaking countries are more likely to be published in an English-language journal rather than a native-language journal if the results are statistically significant (Egger et al., 1997). However, publication bias in this review is less likely given that most risk factor studies do not test an intervention and are therefore unlikely to generate a non-significant outcome that results in a decision not to publish. Third, our inclusion criteria were narrow, resulting in exclusion of many studies of risks for community-onset urosepsis, and more than 700 potential studies in renal transplant and urology patients. This weakened the weight and perhaps the quality of evidence, but strengthened the precision of our results. Fourth, our use of two different checklists to appraise potential for bias did not allow for a direct comparison of quality across all studies. However, the purpose of using the checklists was to help us identify bias within studies, rather than to rate and compare quality across studies. Finally, we were not able to conduct a meta-analysis or quantitative synthesis of any single risk factor because of the heterogeneity of outcome definitions and the variety of risk factors examined.
Urol Nurs. 2015;35(4):191-203. © 2015 Society of Urologic Nurses and Associates