Journal Club: Frequent Fliers, Internal and External Validity, and the Problem With Making Continuous Variables Binary
Refers to article:
Comparisons of High Versus Low Emergency Department Utilizers in Sickle Cell Disease
, 17 October 2008
Imoigele P. Aisiku, Wally R. Smith, Donna K. McClish, James L. Levenson, Lynne T. Penberthy, Susan D. Roseff, Viktor E. Bovbjerg, John D. Roberts
Annals of Emergency Medicine
May 2009 (Vol. 53, Issue 5, Pages 587-593) Abstract |
Full Text |
Full-Text PDF (290 KB)
Editor's Capsule Summary for Aisiku et al on Sickle Cell Disease1
What is already known on this topic: Patients with sickle cell disease seeking emergency department (ED) treatment for painful “crises” are often stigmatized as opioid abusers or misusers.
What question this study addressed: This 232-patient cohort study compared clinical andhematologic characteristics of high and low ED utilizers.
What this study adds to our knowledge: Frequent ED use is associated with high disease severity, as reflected by hematologic variables, presence of avascular necrosis, high transfusion requirements, and hydroxyurea treatment.
How this might change clinical practice: Although the study has some limitations, emergency physicians should be aware that for many patients with this disease, frequent ED use is solely a result of high disease severity.
Discussion Points
1.As stated in its title, this study1 seeks to compare patients with sickle cell disease who are frequent and infrequent users of the emergency department (ED). The authors recruited patients from “established [sickle cell disease] clinics, health fairs, referrals, and targeted mailings.”A. Contrast this study design to one in which all patients were recruited from ED logs. Draw a Venn diagram comparing the patients likely to be included in these 2 designs. How do the populations differ?B. Describe the pros and cons of each approach focusing on internal and external validity.C. What techniques might be used to overcome the limitations of each approach?D. What ethical issues arise in each study design?E. Read the abstract's conclusions. How might you modify them? How might you modify the limitations section?
2.Patients were asked to keep a daily diary for 6 months, though investigators included patients who completed as few as 30 of the 188 study days. Each subject's data were extrapolated to create 1-year values. Examine the paper's figure.A. What pattern do you see on the far left of the figure about the number of ED visits by infrequent users? How do you explain this pattern? Does this figure represent the true frequencies or an artifact of the study methods? How could a patient have 1 ED visit per year, given the way data were handled in this study?B. These authors defined frequent users as patients who had at least 3 ED visits per year. According to your clinical experience, are there alternate definitions that might be used? Considering Figure 1, do you think that other definitions might be warranted?
3.The authors write, “[Al]though the data were not statistically significant, high ED utilizers trended toward a higher incidence of anxiety, higher incidence of avascular necrosis and higher WBC count.” Write a sentence that starts, “Although data were not statistically significant, low ED utilizers trended toward …” Discuss the meaning of their and your sentence. What are some problems with this approach? How else might the authors have conveyed this information?
4.The authors suggest that the “frequent flyer” designation that some emergency physicians give to patients who visit often for sickle cell pain is unjustified because, on average, these patients were sicker than infrequent users.A. Honestly examine your own feelings about the “frequent flyer” designation. Do you use the term? How do you feel when others use it? Do you view patients who come in often differently? Do you manage their treatment differently? Do you worry that you may miss a change in their chronic condition? How do you balance pragmatic and moral concerns related to this issue?B. Similarly, what is your approach to pain management in patients who frequently come to the ED complaining of chronic or acute-on-chronic pain? How does your behavior compare with that of your peers? What arguments do you invoke to justify your approach?
Reference
1. 1Aisiku IP, Smith WR, McClish DK, et al.Comparisons of high versus low emergency department utilizers in sickle cell disease. Ann Emerg Med. 2009;53:587–593. Abstract | Full Text |
Full-Text PDF (289 KB)
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CrossRef
aDepartment of Emergency Medicine, Keck School of Medicine/ University of Southern California, Los Angeles, CA
Section editors: Tyler W. Barrett, MD; David L. Schriger, MD, MPH
Editor's Note: You are reading the ninth installment of Annals of Emergency Medicine Journal Club. This bimonthly feature seeks to improve the critical appraisal skills of emergency physicians and other interested readers through a guided critique of actual Annals of Emergency Medicine articles. Each Journal Club will pose questions that encourage readers—be they clinicians, academics, residents, or medical students—to critically appraise the literature.
During a 2- to 3-year cycle, we plan to ask questions that cover the main topics in research methodology and critical appraisal of the literature. To do this, we will select articles that use a variety of study designs and analytic techniques. These may or may not be the most clinically important articles in a specific issue, but they are articles that serve the mission of covering the clinical epidemiology curriculum. Journal Club entries are published in 2 phases. In the first phase, a list of questions about the article is published in the issue in which the article appears. Questions are rated “novice,” () “intermediate,” () and “advanced” () so that individuals planning a journal club can assign the right question to the right student. The answers to this journal club will be published in the October 2009 issue. US residency directors will have immediate access to the answers through the Council of Emergency Medicine Residency Directors Share Point Web site. International residency directors can gain access to the questions by going to http://www.emergencymedicine.ucla.edu/annalsjc/ and following the directions. Thus, if a program conducts its journal club within 5 months of the publication of the questions, no one will have access to the published answers except the residency director. The purpose of delaying the publication of the answers is to promote discussion and critical review of the literature by residents and medical students and discourage regurgitation of the published answers.
It is our hope that the Journal Club will broaden Annals of Emergency Medicine's appeal to residents and medical students. We are interested in receiving feedback about this feature. Please e-mail journalclub@acep.orgwith your comments.
FULL TEXT
Comparisons of High Versus Low Emergency Department Utilizers in Sickle Cell Disease
A. Contrast this study design to one in which all patients were recruited from ED logs. Draw a Venn diagram comparing the patients likely to be included in these 2 designs. How do the populations differ?
B. Describe the pros and cons of each approach focusing on internal and external validity.
C. What techniques might be used to overcome the limitations of each approach?