CIDRAP ASP Journal Club - October 2016

Yu D, Stach L, Newland JG, et al. Integrating a rapid diagnostic test and antimicrobial stewardship: optimizing discharge antibiotics in skin and soft tissue infections. Pediatr Infect Dis J 2016 (published online Sep 19)

Why is this topic important?
Use of rapid diagnostic tests to improve targeting of antimicrobial therapy is an important strategy for antimicrobial stewardship in acute-care settings. According to recent guidelines from the Infectious Diseases Society of America (IDSA) and the Society for Healthcare Epidemiology of America (SHEA) for implementing antibiotic stewardship programs (ASPs), “Availability of rapid diagnostic tests is expected to increase; thus, [hospital] antimicrobial stewardship programs must develop processes and interventions to assist clinicians in interpreting and responding appropriately to results.”1 The guidelines indicate the recommendation to use rapid testing on blood specimens is “weak” and evidence to support use of such tests on blood specimens is of “moderate quality.”1 Additional research is needed to accurately determine the benefit of these clinical practice tools. While this study did not look at rapid testing for bacteremia (which is what the IDSA/SHEA guidelines address), the information provided contributes to available literature on the use of rapid testing to enhance stewardship and promote targeted antibiotic use.


What were the goals of the study?
The goals were to: (1) improve targeted antibiotic therapy for treatment of purulent skin and soft-tissue infections (SSTIs) caused by methicillin-sensitive Staphylococcus aureus (MSSA) in children following introduction of a penicillin binding protein 2a (PBP2a) antigen test and (2) examine whether or not PBP2a antigen testing affected hospital length of stay.


What methods did the authors use?
The investigators conducted a pre- and post-intervention quality improvement project in a single free-standing children’s hospital. The intervention consisted of: (1) PBP2a antigen testing in the microbiology lab for all wound, abscess, and skin cultures, if the patient remained hospitalized at the time of culture growth; (2) reporting of PBP2a testing results to the ASP pharmacist, who provided treatment recommendations if necessary (during regular business hours Monday through Friday); and (3) provider education via lectures and e-mails about PBP2a antigen testing before and periodically during the study period. For both pre- and post-intervention groups, charts were reviewed for empiric antibiotic selection, whether or not the patient was discharged prior to final culture and susceptibility, discharge antibiotic, and hospital length of stay. For the post-intervention group, the investigators also noted if antibiotic therapy was modified prior to final susceptibilities, accuracy of the rapid antigen test, and time between availability of the PBP2a test result and availability of routine automated-system culture and susceptibility. Appropriate targeted therapy for MSSA SSTI was defined as use of a beta-lactam antibiotic and for MRSA (methicillin-resistant S aureus) SSTI was defined as use of an antibiotic to which the isolate was susceptible.

The authors used the PBP2a Culture Colony Test (Alere; Waltham, Mass.), which is a Food and Drug Administration–approved rapid immunochromatographic qualitative assay for detecting PBP2a directly from S aureus culture isolates to aid in identification of MRSA. Test results are available in 6 minutes. Final susceptibility was determined by an automated system (VITEK2; bioMerieux; Marcy l'Etoile, France).
 

What did they find?
The researchers reviewed 224 patient records for the study: 121 in the pre-intervention group (Jul 1, 2012, through Jun 30, 2013) and 103 in the post-intervention group (Jan 1, 2014, through Dec 31, 2014). MSSA was isolated in 52 (43%) and 51 (50%) of patients in the pre- and post-implementation groups, respectively (P = 0.33). Key findings include the following:

  • Most patients received an initial antibiotic with anti-MRSA activity (98% and 94% in the pre- and post-implementation groups, respectively). The primary empiric antibiotic was clindamycin (n=207, 92%).

  • Targeted therapy increased significantly post-implementation for both the overall group (from 74% to 88%; P = 0.008) and the MSSA subgroup (44% to 80%, P < 0.001).

  • Median length of stay for the pre-intervention group was 60 hours (range, 15-229 hours) and for the post-intervention group was 47 hours (range, 17-123) (P = 0.018). 

  • In the post-intervention group, 55 of 103 patients (53%) were already receiving appropriate therapy or had an infectious diseases consult. For the remaining 48 patients, the clinical care team appropriately modified antibiotics based on PBP2a results without ASP intervention (n=23), the ASP team made a recommendation for a change of therapy (n=14), or a missed opportunity for intervention occurred (n=11). Multiple factors contributed to the missed opportunities, including the hours that ASP input was available and pharmacist workflow issues.
     

What are the major study limitations?

  • This was a relatively small study at a single site, which limits the generalizability of the findings.

  • There were a number of missed opportunities for the intervention to occur, which may have limited the detected impact. For example, ASP review occurred only during regular weekday business hours. Also, according to the authors, “There were missed opportunities for PBP2a testing during the initial integration of testing into the microbiology laboratory workflow.”
     

What are the practice and policy implications?
The results demonstrate a benefit of using PBP2a antigen testing for earlier detection of MSSA to improve targeting of antibiotics—particularly for limiting prolonged use of clindamycin. The findings also suggest that provider education about the test led to improved results, since the clinical care team modified treatment for about one fourth of the MSSA patients based on PBP2a testing, before an ASP recommendation to do so.

The investigators pointed out that there were a number of missed opportunities for the intervention, in part because of workflow issues such as having ASP review only available during regular weekday business hours. Minejima and Wong-Beringer recently published an excellent review article on the use of rapid diagnostics as part of antimicrobial stewardship.2 In that review, they stated, “As more institutions consider how to integrate these powerful tools into their clinical practice, the optimal workflow to maximize the benefit of these tools requires thoughtful consideration. Close coordination between the microbiology laboratory, members of ASP, and buy-in from key administrators is needed. Depending on the resources available, the feasibility of real-time feedback may be challenging.”

Topics for discussion: Your feedback welcome!

  1. Do you have other considerations about this study?

  2. Do you agree with the policy implications, or are there others that should be noted?

  3. Would these findings have any impact on your hospital ASP program?

  4. How likely are you to use this test in your hospital to aid in antibiotic prescribing?

  5. Do you think that providing ASP support for interpretation of rapid tests only during weekday regular business hours is sufficient?

  6. Do you think that provider education and training, provision of algorithms, or written protocols for interpretation of rapid test results could significantly decrease the need for additional ASP intervention, and thus decrease the burden on the ASP team?  
     

References

  1. Barlam TF, Cosgrove SE, Abbo LM, et al. Implementing an antibiotic stewardship program: guidelines by the Infectious Diseases Society of America and the Society for Healthcare Epidemiology of America. Clin Infect Dis 2016 May 15;62(10):e51-77
  2. Minejima E, Wong-Beringer A. Implementation of rapid diagnostics with antimicrobial stewardship. Expert Rev Anti Infect Ther 2016 (published online Sep 19)

 

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