Answering your questions.
Q What is your opinion on the appropriate colony count for working up a positive urine culture? Our hospital presently works up all urine with a colony count greater than 10,000. Several other local hospitals work up urines with colony counts greater than 100,000. What do you feel is the most appropriate protocol?
A Urinary-tract infections may be symptomatic or asymptomatic. The criteria used for most microbiological assessments of urine specimens are dependent on the type of specimen submitted and the clinical history of the patient. Table 1 lists general guidelines for urine-culture interpretation and work-up. We know, however, that clinical history does not often accompany the specimen to the laboratory, so we are left to try to do the best analysis possible for the patient--without the luxury of knowing the patient. Significance of urinary-tract pathogens should start at 1[0.sup.4] CFU/mL with CCMS or IDC urine specimens, as it is likely that a significant proportion of patients with both symptomatic and asymptomatic infections have fewer than 1[0.sup.5] CFU/mL of urine. With these two things in mind, Table 2 describes a simplified process, which may be employed.
--Susan E. Sharp, PhD (DABMM) Director of Microbiology
Kaiser Permanente Pathology Regional Laboratory; Associate Professor
Oregon Health and Science University Portland, OR
(1.) Forbes BA, Sahm DF, Weissfeld AS, eds. Bailey and Scott's Diagnostic Microbiology. 10th edition. St. Louis, MO: Mosby; 1998:359-361.
(2.) Mandell GL, Bennett JE, Dolin R, eds. Principles and Practices of Infectious Diseases, 5th edition. New York, NY: Churchill Livingston; 2000:782-784.
Spinning bloody urine
Q I have observed a practice by technologists at multiple institutions for which I cannot find a reference or validation. The technologists are spinning down grossly bloody urine samples and then performing urine dipstick tests. Does anyone have a reference for or thoughts on this practice? My policies do not support this practice, and it must stop. I, however, want to be open-minded about possible alternatives.
A In general, reagent-strip protocol requires the testing of well-mixed, uncentrifuged urine. This is done to ensure detection of only a few intact red-blood cells in the urine specimen. The presence of only a few intact (non-hemolyzed) red cells would be missed if the urine were centrifuged and only the supernatant tested. The reagent-strip test area for "blood" is equally sensitive to hemoglobin and myoglobin. It will detect (react with) intact red cells, which are seen as spots on the reacted reagent area, when small numbers of cells are present. The presence of leukocyte esterase in supernatant urine may also be missed if only intact granulocytes are present in the urine. Other constituents tested for with multiple reagent strips are dissolved in the urine specimen, and results would be the same on both well-mixed specimen and supernatant.
If a urine specimen is grossly bloody, the presence of many red blood cells may obscure or mask color development of the reagent pads, resulting in color interference. To avoid this interference, our clinical laboratory protocol states that "Very bloody specimens should be ... spun and
the supernatant tested [with reagent strips] for the chemistry because of the color interference." An aliquot of the well-mixed urine specimen is centrifuged and the supernatant urine tested with reagent strips to avoid this color interference. Results may be read visually or by instrumentation. Unfortunately, if the red cells are also sufficiently hemolyzed, color interference may persist. This may be determined by observing the gross color of the supernatant.
--Karen M. Ringsrud, MT(ASCP) Assistant Professor Department of Laboratory Medicine and Pathology University of Minnesota Medical School Minneapolis, MN
Cord blood labeling
Q Our lab recently went through JCAHO inspection. We were performing a cord-blood gas, and the inspector was watching. The lab has always labeled the specimen with the baby's name and charged to the baby's account. I have seen it done this way at other labs as well as here.
The inspector said that the sample should be labeled with the mother's name and charged to the mother's account. I find this odd because the sample is the baby's blood. Can you offer some advise on this issue?
A There are two issues to discuss here. First, whose blood is being tested? Blood gasses on cord blood are done on oxygenated blood from the umbilical vein. This blood is in the baby's circulation, and the cells are the baby's. Therefore, the test is being performed on the baby. Second, what is the proper role for an accreditation or licensing inspector? The inspector's role is to see that there is a label that follows the lab's written policy and procedure on how the specimen should be labeled. There are no regulatory or accreditation rules that specify in a situation like this whose name should be on the specimen. The rules do say that there must be a unique identifier on the specimen container. The lab's policy and procedure could go either way as far as whether to give the baby's name or the mother's name. It just has to be written and followed. An inspector might have an opinion about the labeling or charging method used by the lab but cannot use this as a basis for a deficiency or to make a change in the lab's policy.
--Daniel M. Baer, MD Professor Emeritus Department of Pathology Oregon Health and Science University Portland, OR</p> <pre> Table 1. General guidelines for urine-culture interpretation and work-up. Result
Specimen type Work-up
history [greater than or equal to] 1[0.sup.4] CCMS or IDC Work up both CFU/mL of a single potential pathogen urine specimens organisms or for each of two potential pathogens from patients
with ID and with
specimens [greater than or equal to] 1[0.sup.3]
CCMS or IDC Work up CFU/mL of a single potential pathogen urine in potential symptomatic pathogen male patients with ID and OR Straight AST catheter urine specimens, OR
specimens [greater than or equal to] Three CCMS or IDC No work up organisms urine specimens
specimens One potential pathogen at [greater CCMS or IDC Work up the than or equal to] 1[0.sup.4] CFU/mL urine specimens one organism with one to two organisms at <
at [greater 1[0.sup.4] CFU/mL
CFU/mL [greater than or equal to] 1[0.sup.2] Suprapubic
Work up CFU/mL of up to three potential urine aspirates potential pathogens or other pathogens surgical (up to obtained urine three) with specimens ID and AST (e.g.,
specimens) </pre> <pre> Table 2. Simplified process for urine-culture interpretation and work-up. Specimen Result
Work-up type CCMS or [greater than or equal to] 1[0.sup.4] Work up IDC urine CFU/mL of one or two potential organism(s) specimens pathogens
with ID and
AST. CCMS or One potential pathogen at [greater Work up the IDC urine than or equal to] 1[0.sup.4] CFU/mL one organism specimen with one to two organisms at < at [greater 1[0.sup.4] CFU/mL than or
CFU/ml Straight [greater than or equal to] Work up catheterized 1[0.sup.3] CFU/mL of one organism(s) urine specimens to two potential pathogens with ID and
AST. Suprapubic urine > 1[0.sup.2] CFU/mL Work up aspirates or other of up to three
potential surgical obtained potential pathogens
pathogens urine specimens
(up to (e.g., cystoscopy
three) with specimens)
ID and AST. Key: CCMS = Clean-catch midstream IDC = Indwelling catheter ID = Identification AST = Antimicrobial susceptibility testin </pre> <p>Edited by Daniel M. Baer, MD
Daniel M. Bear, MD, is professor emeritus of laboratory medicine at Oregon Health and Science University in Portland, OR, and a member of MLO's editorial advisory board.
MLO's "Tips from the Clinical Experts" provides practical, up-to-date solutions to readers' technical and clinical issues from a panel of experts in various fields. Readers may send questions to Dan Baer by e-mail at firstname.lastname@example.org.
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|Title Annotation:||Tips from the clinical experts|
|Author:||Baer, Daniel M.|
|Publication:||Medical Laboratory Observer|
|Article Type:||Panel Discussion|
|Date:||Feb 1, 2006|
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