SEARCH

SEARCH BY CITATION

Keywords:

  • evidence-based medicine;
  • algorithms;
  • databases;
  • bibliographic;
  • database management systems;
  • information storage;
  • retrieval;
  • methods;
  • urology;
  • PubMed
Abbreviations
ER

emergency room

EBCP

evidence-based clinical practice

RCT

randomized controlled trial.

CASE SCENARIO

  1. Top of page
  2. CASE SCENARIO
  3. CLINICAL QUESTION
  4. FINDING THE BEST EVIDENCE
  5. DEVELOPING A SEARCH STRATEGY IN PUBMED
  6. APPLYING PUBMED TO THE CLINICAL QUESTION
  7. APPLYING THE RESULTS TO THE CARE OF YOUR PATIENT
  8. CONCLUSION
  9. CONFLICT OF INTEREST
  10. REFERENCES

You are the on-call urologist consulted by the emergency room (ER) for acute flank pain in a 44-year-old woman. The patient denies any previous history of stones and is otherwise healthy. Non-contrast enhanced abdominal and pelvic CT shows a 4-mm calculus at the vesico-ureteric junction. Urine analysis shows no infection and traces of blood. Her pain and nausea are controlled in the ER. You recommend an α-blocker to promote stone passage, which is met with some scepticism by the ER physician, who queries you whether there is more than anecdotal evidence for this recommendation, which prompts you to search the medical literature.

CLINICAL QUESTION

  1. Top of page
  2. CASE SCENARIO
  3. CLINICAL QUESTION
  4. FINDING THE BEST EVIDENCE
  5. DEVELOPING A SEARCH STRATEGY IN PUBMED
  6. APPLYING PUBMED TO THE CLINICAL QUESTION
  7. APPLYING THE RESULTS TO THE CARE OF YOUR PATIENT
  8. CONCLUSION
  9. CONFLICT OF INTEREST
  10. REFERENCES

The classic steps in evidence-based clinical practice (EBCP) involves the five As: Assess, Ask, Acquire, Appraise and Apply [1]. ‘Assess’ refers to a specific patient-care issue where the physician identifies a need for more information. The astute physician ‘Asks’ a focused, answerable question generated from the clinical situation. The mnemonic ‘PICOT’ is helpful in outlining the clinical query. PICOT stands for patient, intervention, comparison, outcome and type of study. In the aforementioned scenario, the patient is a woman with a urinary stone. Various therapies could constitute the intervention and comparison; thus each PICOT is driven by the particular needs of the patient. For this specific patient, you formulate the following clinical question: ‘In adults (female) with urinary stones, are α-blockers more effective than usual care in promoting stone passage?’

FINDING THE BEST EVIDENCE

  1. Top of page
  2. CASE SCENARIO
  3. CLINICAL QUESTION
  4. FINDING THE BEST EVIDENCE
  5. DEVELOPING A SEARCH STRATEGY IN PUBMED
  6. APPLYING PUBMED TO THE CLINICAL QUESTION
  7. APPLYING THE RESULTS TO THE CARE OF YOUR PATIENT
  8. CONCLUSION
  9. CONFLICT OF INTEREST
  10. REFERENCES

The next step in the EBCP is to ‘Acquire’ the evidence. While there are several electronic resources to use in answering the clinical question, this review will focus on PubMed, a free service of the US National Library of Medicine that searches the Medline database. PubMed includes >18 million citations from Medline and other life-science journals for biomedical articles back to 1948. As reviewed in a previous article in this series, we are interested in types of studies that are most likely to provide an unbiased answer to our question [2]. In this example, our question relates to therapy and would best be answered by a randomized controlled trial (RCT) or better yet, by a systematic review of all RCTs on this particular subject.

DEVELOPING A SEARCH STRATEGY IN PUBMED

  1. Top of page
  2. CASE SCENARIO
  3. CLINICAL QUESTION
  4. FINDING THE BEST EVIDENCE
  5. DEVELOPING A SEARCH STRATEGY IN PUBMED
  6. APPLYING PUBMED TO THE CLINICAL QUESTION
  7. APPLYING THE RESULTS TO THE CARE OF YOUR PATIENT
  8. CONCLUSION
  9. CONFLICT OF INTEREST
  10. REFERENCES

Searching for articles in PubMed follows a simple process: formulate your PICOT, search each concept separately, check Details to verify you are using appropriate terms, combine your concepts with the correct connectors (‘AND’ or ‘OR’), and use appropriate limits. Before starting the search it is important to understand how PubMed is organized. Each citation in the database can be searched for the exact words used by the author in the title and abstract, as well as for the subject terms known as Medical Subject Headings, or MeSH. MeSH terms are added to the citation by an indexer and help to identify articles by topic, regardless of the exact words used by the author. For example, searching with the MeSH term urinary calculi will retrieve articles that discuss urinary stones, urinary calculi, urinary tract stones, ureteral(ic) stones, urinary tract calculi, etc. PubMed will automatically try to match the search terms to the proper MeSH terms. (For more information about using MeSH see http://www.ncbi.nlm.nih.gov/sites/entrez?db=mesh)

For our clinical question, we need to find articles that discuss urinary stones and α-blockers within the context of RCTs or a systematic review. We can begin by entering individual terms from the PICOT, such as the patient problem of urinary stones into the search field (Fig. 1A) and hit the Go button. To verify that PubMed matched our words to an appropriate MeSH term, click on the Details to show that urinary stones matched to the MeSH term urinary calculi (Fig. 1B). The next step is to search for α-blockers as the intervention of interest. Enter the words alpha blockers in the Search Field and hit the Go button. Again, using the Details tab, note that PubMed matched this common phrase to the MeSH terms Adrenergic alpha Antagonists and Adrenergic alpha Antagonists [pharmacological action]. This will retrieve articles that discuss this group of drugs, as well as articles about specific α-blockers such as tamsulosin, that have the pharmacological action of α-blockers. Under the History tab, we now have two sets of articles, one discussing urinary stones and another set discussing α-blockers. To identify those articles that discuss both topics, we need to combine the sets with the connector AND. The AND requires that both concepts be in the same article and is used to narrow the search strategy. OR requires that at least one of the terms be in the article; it is used for synonyms and to broaden the search strategy. Note that PubMed requires a specific format for combining search sets, such as ♯1 and ♯2. The final step is to limit the combined set to RCTs or systematic reviews. Use the Limits tab to select RCT from ‘Type of Article’ or Systematic Reviews from ‘Subset/Topic’. Other useful limits include English language, date ranges and age groups.

imageimage

Figure 1. Screen shots of A, the search field in PubMed; B, verifying the term urinary stones matched to appropriate MeSH terms; and C, the results of the search strategy implemented.

There are several additional features of PubMed that allow you to save searches, store citations, and use predefined search filters that help to find the most appropriate study design for the type of question being asked (Clinical Queries). For more information about these special features of PubMed contact your medical librarian or review the helpful tutorials at http://www.nlm.nih.gov/bsd/disted/pubmed.html.

APPLYING PUBMED TO THE CLINICAL QUESTION

  1. Top of page
  2. CASE SCENARIO
  3. CLINICAL QUESTION
  4. FINDING THE BEST EVIDENCE
  5. DEVELOPING A SEARCH STRATEGY IN PUBMED
  6. APPLYING PUBMED TO THE CLINICAL QUESTION
  7. APPLYING THE RESULTS TO THE CARE OF YOUR PATIENT
  8. CONCLUSION
  9. CONFLICT OF INTEREST
  10. REFERENCES

The results should provide you with 28 RCTs or seven systematic reviews on this topic (Fig. 1C). These include a systematic review and meta-analysis by Hollingsworth et al. published in The Lancet[3]. The last steps in EBCP are to ‘Appraise’ the evidence for the validity of the study methods. Using the criteria from the ‘Users’ Guide to the Medical Literature’ you find the study to be a well-designed systematic review that is likely to yield valid results, although you notice that the underlying studies appear to be of limited methodological quality [4]. You also find the results to be clinically important, with a 65% (95% CI 45–88%) increased probability of stone passage with medical therapy.

APPLYING THE RESULTS TO THE CARE OF YOUR PATIENT

  1. Top of page
  2. CASE SCENARIO
  3. CLINICAL QUESTION
  4. FINDING THE BEST EVIDENCE
  5. DEVELOPING A SEARCH STRATEGY IN PUBMED
  6. APPLYING PUBMED TO THE CLINICAL QUESTION
  7. APPLYING THE RESULTS TO THE CARE OF YOUR PATIENT
  8. CONCLUSION
  9. CONFLICT OF INTEREST
  10. REFERENCES

Having determined the study to be valid, yielding clinically important results that appear to be relevant to your patient, you are now ready to ‘Apply’ the evidence to the care of your individual patient. Whereas one would expect most patients to be interested in medical expulsive therapy, there is no automatic mandate to applying certain forms of therapy in evidence-based medicine, even in the presence of compelling high-quality evidence for its benefit. Instead, one needs to consider the patient’s values, preferences and circumstances. For example, depending on the healthcare environment in which you are practising, the patient might find the costs of medical therapy to be prohibitive. Lastly, the patient’s motivation to pursue medical therapy might hinge on her baseline probability of passing her stone spontaneously. In the study by Hollingsworth et al.[3] the number-needed-to-treat was four, based on an average baseline stone passage rate of 47% in the control group. However, if we assumed a lower probability of passing the stone spontaneously of only 20% (e.g. in a patient with an 8-mm proximal ureteric stone) the number-needed-to-treat would increase to eight (95% CI 6–16). Even though this still represents an effective treatment, this example illustrates the need to consider the baseline risk when considering the anticipated benefit of treatment to a patient.

CONCLUSION

  1. Top of page
  2. CASE SCENARIO
  3. CLINICAL QUESTION
  4. FINDING THE BEST EVIDENCE
  5. DEVELOPING A SEARCH STRATEGY IN PUBMED
  6. APPLYING PUBMED TO THE CLINICAL QUESTION
  7. APPLYING THE RESULTS TO THE CARE OF YOUR PATIENT
  8. CONCLUSION
  9. CONFLICT OF INTEREST
  10. REFERENCES

PubMed represents a free and readily accessible tool to search the medical literature for the answer to clinical questions that arise in the routine care of urological patients. Familiarity with the search process and specific functions of PubMed allows users to search the medical literature effectively by narrowing the search to studies most likely to provide valid and clinically relevant evidence, thereby facilitating an EBCP of urology.

REFERENCES

  1. Top of page
  2. CASE SCENARIO
  3. CLINICAL QUESTION
  4. FINDING THE BEST EVIDENCE
  5. DEVELOPING A SEARCH STRATEGY IN PUBMED
  6. APPLYING PUBMED TO THE CLINICAL QUESTION
  7. APPLYING THE RESULTS TO THE CARE OF YOUR PATIENT
  8. CONCLUSION
  9. CONFLICT OF INTEREST
  10. REFERENCES