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Utilization of the Microbiology Laboratory for Diagnosis of ID
A Guide to Utilization of the Microbiology Laboratory for Diagnosis of Infectious Diseases
The critical role of the microbiology laboratory in infectious
disease diagnosis calls for a close, positive working relationship between the
physician and the microbiologists who provide enormous value to the health care team. This document, developed by both laboratory and clinical experts,
provides information on which tests are valuable and in which contexts, and on
tests that add little or no value for diagnostic decisions. Read full text recommendations.
Feedback welcome. Please send us your comments here.
We have read the exceptionally comprehensive IDSA/ASM Guidelines on laboratory diagnosis (Clin Infect Dis. 2013 Aug;57(4):485-8 ). The microbiology laboratory-provider interface is an area of effort that is under-appreciated in patient care systems, and your outstanding work will help bridge that gap.However, as individuals who care for many children with bacterial enteric infections, and as investigators in the field of gastrointestinal illnesses, we are very concerned about the recommendation for stool specimen submission. Briefly, we strongly believe that the acutely ill patient with diarrhea who warrants testing for a bacterial enteric infection should undergo such evaluation as a matter of priority. We also believe that a policy that encourages specimens submitted in cups hinders that process.
Here are our thoughts:1. Cup specimens are notoriously difficult to obtain, even among the presumably motivated group of patients who visit emergency facilities. Figure 1 in http://cid.oxfordjournals.org/content/43/7/807.long demonstrates just how difficult it is to obtain stool specimens in cups, if left to patient/parent preference.2. There are important specimen custody issues: If a patient can't produce specimen on site, it is very cumbersome to return it to a facility for culture. Questions that arise include: where in the institution should it go? Is the doctor's office open? Are there drop off issues? Did it really come from the patient? Will the right paperwork accompany the specimen?
Also, if a patient is admitted from an emergency facility, there are frequent hand-off glitches, and it is often unclear if a test is truly pending, or has merely been ordered. There is no value in delaying taking possession of a specimen that could contain a bacterial pathogen, and considerable value in accelerating the time to result (even if negative).3. It is difficult to state with certainty, but biohazard control might be easier to implement using a contained swab culture system than a patient - managed cup specimen. Specifically, the sheathed swab system seems more hygienic.4. The "rectum to plate" interval is shorter using a swab-based protocol than a cup from home to an institution or office to a laboratory pathway. A few hours gained by sending a swab on presentation could result in a day earlier time to result.5. If a patient with diarrhea presents to an ER, the organisms that are traditionally the most important to find (i.e., bacterial enteric pathogens) are not those best diagnosed in cup specimens (though we do acknowledge access issues play a role in choice of place of presentation of less than acute illnesses to acute care facilities).
6. The references cited in the Guidelines as supporting the superiority of cup stool specimens do not demonstrate the inferiority of swab cultures. Reference 106 (Diagn Microbiol Infect Dis 2006;56:123-6) pertains only to Salmonella, and, in fact, finds merit in testing both cups and swabs. Reference 107 (J Clin Microbiol 2007;45:1278-83) reports that bulk stool and swabs have equivalent yields for bacterial enteric pathogens.
Phillip I. Tarr, M.D.Melvin E. Carnahan Professor of PediatricsProfessor of Molecular MicrobiologyDirector, Division of Pediatric Gastroenterology, Hepatology and NutritionCo-Leader, Pathobiology Research Unit, Washington University School of Medicine
Lori Holtz, M.D.
Assistant Professor of Pediatrics, Division of Gastroenterology, Hepatology & Nutrition
Washington University School of Medicine
Ryan McKee, M.D.
Clinical Fellow, Division of Pediatrics Emergency Medicine
David Schnadower, M.D., M.P.H.Fellowship Director, Division of Pediatric Emergency MedicineWashington University School of Medicine
Rebecca Stolle, R.N.
St. Louis Children's Hospital
Donna M. Denno, M.D., M.P.H.
Associate Professor of Pediatrics
Adjunct Associate Professor, Health Services Departments of Pediatrics and Global Health
University of Washington
Eileen J. Klein, MD, MPH
Fellowship Director, Pediatric Emergency Medicine
Co-Director, Emergency Department Research
University of Washington and Seattle Children's Hospital
Stephen B. Freedman, .M.D.C.M., M.S.c.
Sections of Pediatric Emergency Medicine and Gastroenterology
Alberta Children's Hospital and University of Calgary
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