A Search Someone Else Could Repeat: Documenting the Evidence Search on Contaminated Blood Cultures From Emergency Patients
Student Name
Doctor of Nursing Practice Program, Aspen University
DNP860: Evidence-Based Practice for Quality Improvement
Instructor Name
Month Day, Year
A Search Someone Else Could Repeat: Documenting the Evidence Search on Contaminated Blood Cultures From Emergency Patients
A literature search is part of the evidence, not a preliminary to it. If the search misses important studies, the appraisal and recommendations that follow will be incomplete, and if the search is not documented, no one can judge what it missed. This paper documents the search for evidence to answer the PICOT question developed in the previous module, with enough detail that another reader could repeat it: the question's concepts, the databases, subject headings and keywords, search strings, limits, results at each stage, and the reasons studies were excluded.
Breaking the Question Into Concepts
The question from the previous module compares a three-part collection bundle with current practice for adults in the emergency department, with contamination rate over six months as the outcome. Three concepts carry the search: blood cultures; contamination or false-positive results; and collection practices, including venipuncture, catheter draws, phlebotomy teams, sterile technique, and diversion devices. The emergency department setting was not used as a required concept, because many relevant studies were conducted hospital-wide and their findings apply to the emergency department.
Databases and Sources
Four sources were searched: PubMed, which includes MEDLINE; CINAHL Complete, for nursing literature; the Cochrane Library, for systematic reviews; and Google Scholar, for studies and gray literature not indexed elsewhere, with the first 200 results screened. Embase was not available through the university library. This matters, because a study of database combinations for systematic reviews found that 16 percent of included references were found in only one database, that Embase produced the most unique references, and that the combination of Embase, MEDLINE, Web of Science, and Google Scholar performed best (Bramer et al., 2017). The absence of Embase is therefore stated as a limitation, and reference lists of included studies and reviews were checked to reduce the risk of missing studies. Guidance documents from professional laboratory and infection prevention organizations were also sought.
Subject Headings, Keywords, and Search Strings
Each concept was searched with both controlled vocabulary and free-text keywords, combined with OR within concepts and AND between them. The PubMed string was: ("Blood Culture"[Mesh] OR "blood culture*"[tiab]) AND ("Equipment Contamination"[Mesh] OR contaminat*[tiab] OR "false positive*"[tiab] OR pseudobacteremia[tiab]) AND ("Specimen Handling"[Mesh] OR "Phlebotomy"[Mesh] OR venipuncture[tiab] OR phlebotom*[tiab] OR catheter*[tiab] OR diversion[tiab] OR "sterile technique"[tiab] OR "collection practice*"[tiab]). In CINAHL, the equivalent CINAHL subject headings were used with the same keywords. The Cochrane Library was searched with the keywords "blood culture" AND contamination.
Limits
Limits were English language, publication from January 2005 to the search date, and human studies. The date limit reflects changes in blood culture systems and collection devices; seminal earlier studies were identified through reference lists. No study design limit was applied, because relevant evidence includes randomized and controlled trials, quality improvement studies, and systematic reviews.
Results and Screening
The searches returned 412 records in PubMed, 196 in CINAHL, 3 in the Cochrane Library, and 200 screened results in Google Scholar. After removing duplicates, 489 records remained. Title and abstract screening excluded 438 records that addressed laboratory methods, pediatric or neonatal populations only, or catheter-related bloodstream infection rather than contamination. Full texts of 51 records were reviewed, and 37 were excluded: 14 did not report contamination rates, 11 were opinion pieces without data, 8 studied only one organism, and 4 were conference abstracts without full reports. Fourteen sources were included, along with 2 identified from reference lists, for a total of 16. Every excluded study has a stated reason, so a reader who disagrees with a decision can see exactly where it was made.
Screening Process and Reliability
Screening was done in two stages by two reviewers, the DNP student and an emergency nurse on the project team, using written inclusion criteria: adult or mixed populations, blood cultures collected in hospital settings, an intervention or practice related to collection, and a reported contamination rate. Both reviewers screened the same first 50 titles and abstracts independently and agreed on 46, after which they discussed the four disagreements and clarified the criteria. The remaining records were divided between them, with any uncertain record reviewed by both. Full texts were reviewed by both reviewers, and disagreements were resolved by discussion with the infection preventionist. A single reviewer working alone is more likely to exclude relevant studies by mistake, and documenting the agreement check lets readers judge how consistently the criteria were applied.
What the Search Found
The included sources span several levels of evidence. They include a systematic review and meta-analysis of practices to reduce contamination, which found that venipuncture rather than catheter draws and the use of phlebotomy teams reduced contamination, while prepackaged preparation kits did not show a clear effect (Snyder et al., 2012); a prospective controlled trial of an initial specimen diversion device; several quality improvement studies using interrupted time series or before-and-after designs; and a comprehensive review of the problem and its solutions (Doern et al., 2019). The mix of designs will shape the appraisal in the next module, since the strongest evidence exists for some components of the bundle and weaker evidence for others.
Keeping the Search Current
The search was run on a single date, recorded in the search log along with each string and result count. Because the project will run for more than a year, saved searches with email alerts were set up in PubMed and CINAHL so that new publications are flagged monthly. Any new study that meets the inclusion criteria before the final report will be appraised and added, and the report will state the final search date. Gray literature, including laboratory standards and infection prevention guidance, will be rechecked before implementation, since professional guidance on contamination targets and collection practices can change.
Conclusion
The search for evidence on blood culture contamination is documented with its concepts, sources, strings, limits, counts, and exclusions, so that another reader could repeat it and judge its completeness. Its main limitation, the absence of Embase, is acknowledged and partly addressed by reference list checking. Sixteen sources will move forward to appraisal.
References
Bramer, W. M., Rethlefsen, M. L., Kleijnen, J., & Franco, O. H. (2017). Optimal database combinations for literature searches in systematic reviews: A prospective exploratory study. Systematic Reviews, 6, Article 245. https://doi.org/10.1186/s13643-017-0644-y
Doern, G. V., Carroll, K. C., Diekema, D. J., Garey, K. W., Rupp, M. E., Weinstein, M. P., & Sexton, D. J. (2019). Practical guidance for clinical microbiology laboratories: A comprehensive update on the problem of blood culture contamination and a discussion of methods for addressing the problem. Clinical Microbiology Reviews, 33(1), Article e00009-19. https://doi.org/10.1128/CMR.00009-19
Snyder, S. R., Favoretto, A. M., Baetz, R. A., Derzon, J. H., Madison, B. M., Mass, D., Shaw, C. S., Layfield, C. D., Christenson, R. H., & Liebow, E. B. (2012). Effectiveness of practices to reduce blood culture contamination: A Laboratory Medicine Best Practices systematic review and meta-analysis. Clinical Biochemistry, 45(13-14), 999-1011. https://doi.org/10.1016/j.clinbiochem.2012.06.007
How this DNP 860 Module 2 example is structured
DNP860 Module 2 papers typically document a search strategy another reader could repeat exactly. Aspen does not publish module deliverables, so check your classroom for the exact prompt. This example breaks the question into concepts, names and justifies each source, reports full search strings and limits, counts records at each stage with exclusion reasons and previews the evidence found.
DNP860 Module 2 questions, answered
What does DNP860 Module 2 usually ask for?
The module typically asks you to document your literature search for your PICOT question in enough detail that another reader could repeat it, including databases, terms, limits and results. Aspen does not publish module deliverables, so your classroom's instructions govern.
Why combine subject headings and keywords?
Subject headings such as MeSH capture indexed articles on a concept regardless of wording, while keywords capture recent or poorly indexed articles. Combining them with OR within a concept improves recall.
Does it matter which databases I search?
Yes. A study of systematic review searches found that 16 percent of included references were found in only one database, so searching several databases and checking reference lists reduces the risk of missing studies.
Write yours, or have the desk draft it
This paper is an original model document written by our desk, not a submitted student paper and not an official Aspen University document. Read it for the moves, then write your own to the instructions in your classroom. If you want one built to your exact prompt and rubric, the first custom sample is free and arrives in 24 to 48 hours.