Answering your questions on anthrax stains, ergonomic workstations, glucose urine testing on children, site preparation for infant blood cultures, and contaminated urine cultures

Jan. 1, 2002
Edited by Daniel M. Baer, MD

Anthrax stains

Q: What is the best microscopy method for observing anthrax spores? Do the spores fluoresce under ultraviolet light?

A: The spores of Bacillus anthracis do not fluoresce under ultraviolet light, but can be visualized by phase contrast microscopy or after staining with a spore stain. Most routine clinical laboratories (Level A) should not attempt to examine environmental samples (unknown powders suspected of containing anthrax spores) because the potential for aerosolization of the material is so great. 

Your institution should have an emergency plan for handling reports of suspicious powders. If an emergency plan is not in place, contact your state health laboratory for assistance. However, if the suspected material is examined, the procedure must be performed in a Biological Safety Level 3 containment facility.1 The suspected material can be suspended in saline or water and used to prepare a wet mount. Seal the edges of the wet mount, decontaminate the slide with bleach, and view under phase contrast microscopy.2 The spores should be phase bright and regular in shape and size. A spore stain may be used, but often the suspected powder does not adhere to the slide. Additional information on the agents of bioterrorism can be obtained at the CDC website:
www.bt.cdc.gov.

David Sewell, PhD, ABMM
Director of Microbiology
Veterans Affairs Medical Center
Portland, OR

References

1. Biosafety in Microbiological and Biomedical Laboratories. 4th ed. Washington, D.C. U.S. Dept. of Health and Human Services.
CDC-NIH; 1999.

2. Logan. NA and PCB Turnbull. Bacillus and recently derived genera, pp. 357-369, in Manual of Clinical Microbiology, eds. Murray PR, Baron
EJ, Pfaller MA, Tenover FC and RH Yolken. American Society for Microbiology, Washington, D.C., 1999.

Ergonomic workstation

Q: I read your article on lab ergonomics
(MLO Feb.
2001) with great interest. I wonder if you have a contact who would address the problem of using the microscope, counting on a computer keyboard, and viewing the results on a monitor. There seems to be no satisfactory way to form an ergonomically correct workstation to perform all these tasks. Most of the attainable information is related to secretarial stations, lifting, and
pipetting, with little attention to the MT who spends eight hours a day at the scope and the computer.

A: Setting up a body-friendly work-station for employees using a microscope is not unlike setting up a workstation for a computer terminal. The employee should sit in an ergonomically designed chair with two to six adjustments, and the employee should sit at a 90-degree angle at the hips. A good chair is key to comfort while doing differentials. Feet should be flat on the floor, or if the individual is small in stature, he or she might need a foot rest to maintain proper posture.

The top of the counter should support the arm and the keyboard. Sometimes foam padding can help. Often the monitor is on the right or left of the microscope. You might want to try to place the monitor just above the back of the microscope so the head would not have to turn, but rather the eyes could look up to the screen. The monitor should be 23 to 29 inches from the eyes, depending on the focal point.

Recognizing symptoms of ergonomic discomfort can help the employee make adjustments before permanent damage occurs. You can obtain a brochure called The Body-Friendly Workstation by e-mailing your name and mailing address to
[email protected]. The brochure outlines the probable cause of discomfort and possible correction. Issues include posture, keyboarding, vision, hand care, and relaxation exercises. 

For proper workstation review in any area, consult an ergonomist who has training in workstation design. Many larger institutions offer this service to the community through their wellness office or occupational therapy. Sometimes you can find an ergonomist at manufacturing plants that have repetitive motion issues.

Terry Jo
Gile, MT(ASCP), MA Ed.

Administrative Coordinator
Department of Laboratories
Barnes-Jewish Hospital
St. Louis, MO 

Glucose urine tests on children

Q: We perform Clinitest on all pediatric patients. The problem is that our pediatric population is identified as anyone who is 17 years of age or younger. Clinitest is usually performed on children age 5 or younger for the detection of
galactose. What is the clinical significance for performing Clinitest on patients between the ages of 6 and 17? All this testing seems to be a financial waste. 

A: According to the CAP Urinalysis and Clinical Microscopy Proposed Checklist, December 2000, There must be a clearly defined procedure relative to testing pediatric urine specimens for the presence of reducing substances other than glucose. Such a policy may be based on consultation with the pediatric staff. The policy should include instructions for dealing with those urines tested and found to be negative with glucose-specific tapes or strips. There is no requirement for routine performance of reducing substance testing in adult urines. 

The procedure for testing pediatric urine specimens for the presence of reducing substances other than glucose will be somewhat dependent on the neonatal testing program within the state or neighboring states where the laboratory is located. Testing in the laboratory generally employs a copper reduction test for reducing substances, such as the Clinitest Tablet Test (Bayer, Tarrytown, NY). However, when neonatal screening for galactose is in place, urine specimens are generally tested for reducing substances only on patients under the ages of 1 or 2. If the patient population has not been part of a neonatal screening program, an upper age of 5 or 6 might be more appropriate. In addition, the institution may choose to require such testing only once on a given patient. The results of this testing must be documented in the patients permanent record, however.

Karen M. Ringsrud
MT(ASCP)

Assistant Professor
Department of Laboratory
Medicine and Pathology
University of Minnesota Medical School
Minneapolis, MN

Quantitative body fluid counts

Q: We currently offer cell counts on cerebrospinal fluids,
paracenteses, synovial fluids, and other fluids. I can see the importance of reporting both WBC and RBC counts on cerebrospinal fluids, but how important is a cell count for the other fluids? Is it acceptable to report cell counts semi-quantitatively, e.g., RBC 1+, 2+ etc., for these types of fluids?

A: Currently, it is recommended that cell counts on spinal fluids be quantitatively determined, rather than only estimated as 1+. 2+ etc.1 This is because the definitions of such semi-quantitative intervals are not yet standardized, and therefore comparisons with reports from the literature could be problematic.

The examination of spinal fluids for evidence of infection, including bacterial
vs, viral, or cerebral hemorrhage, is particularly important for patient care. There is a temptation to do the quantitative cell counts on the hematology analyzer, although the manufacturers may not recommend that method. But with the increased accuracy and precision of these counters, I would expect contemporary studies will obviate this objection.

Also, the development of cytocentrifigation techniques for spinal fluids as well as other body fluids makes this method very attractive for differential counting, but there are the necessities of purchasing and maintaining an additional piece of equipment and the purchase of disposable devices for the preparation of microscopic slides.

Quantitative cell counts on other fluids, such as urine, have considerable benefits. Interestingly, microbiology laboratories are now using accurate estimates of cell counts on urinalysis to decide which urine specimens should be cultured, and significant savings of time and resources have been achieved. As counts on other fluids improve, hopefully similar improvements would be found for other fluid examinations.

Of course, in addition to quantitative counting, the morphology is also important. Synovial fluids occasionally are submitted to examine and identify any diagnostic crystals as might be seen in gout or other types of arthritis. All of these fluids can conceivably contain malignant cells, and therefore the possibility of such cells must be kept in mind.

John A.
Koepke, M.D.

Professor Emeritus of Pathology
Duke University Medical Center
Durham, NC

General reference

1. Gall, JJ. Laboratory evaluation of body fluids. Chapter 30 in, Clinical Hematology Principles, Procedures, Correlations, 2nd Edition.
Stiene-Martin E, Lotspeich-Steininger & Koepke, JA, editors.
Lippincott, Philadelphia, PA. pp. 400-414, 1997

Site preparation for infant blood cultures

Q: It is impossible to follow the recommendations for site preparation when drawing blood cultures if the patient is a neonate or a young child. The two-minute alcohol/iodine scrub just doesnt happen with the result that our contamination rate on that patient population is a little higher than it should be. Also, the commercially available prep kits are somewhat abrasive. Our phlebotomists have noted that if the swabs are used as they should be, the skin can be literally rubbed off on the neonates. This makes both the patient and the physician very unhappy.

Do you know of any other approved methods for site prep that require a shorter prep time and/or less scrubbing action? 

The phlebotomist needs specifics on doing an alcohol-only scrub when the patient is allergic to
Betadine. Is it the same times and procedures, but using alcohol only? Is there a commercially made alcohol-only kit? The little alcohol pads wont hold up to a two-minute scrub. 

A: The purpose of the alcohol prep is to remove most of the surface dirt, not to kill organisms (although it is marginally bactericidal). Although some texts recommend a two-minute scrub with alcohol, they do not cite a reference to support a minimum time of application. Keep in mind that the critical phase of site sterilization is maintaining that the iodine compound remains in contact with the skin for at least 30 seconds.1 If this time is shortened, its bactericidal effect is compromised. 

The American Society of Microbiology suggests that a facilitys contamination rate ought not to exceed 3 percent of all cultures drawn.2 I suspect a shortened contact time with iodine to be one of the biggest contributors to contamination, along with repalpating the puncture site after sterilization. I agree that the sponges in most commercial site prep kits are probably too coarse to be used as vigorously on infants as they are on older children and adults. Because the application of the iodine compound is the critical phase of blood culture site preparation, it isnt necessary to scrub aggressively on tender skin, and it may not be necessary to scrub for two minutes. I suggest you make sure all your collectors are less aggressive with commercially prepared alcohol scrubs and limit the scrubbing to 30 to 60 seconds. If you are finding that the commercial sponges are still harsh on infant skin, even with minimal scrubbing, I would suggest using the individually wrapped alcohol preps instead. Use several, if necessary. More importantly, make sure your collectors are allowing the iodine to remain in contact with the skin for at least 30 seconds. 

I am going to assume that your phlebotomists are the only ones in your facility that draw blood cultures. If, however, you have nonphlebotomists drawing cultures as well, studies show that when a multi-skilled workforce draws blood cultures, the use of separately packaged alcohol and iodine swabs results in a higher contamination rates than in those facilities that use commercially prepared blood culture prep kits.3 Another study shows that such facilities have higher contamination rates if they use iodine in the form of an iodophor such as povidone rather than in tincture form.4-6 

The National Committee for Clinical Laboratory Standards
(NCCLS) recommends that the stoppers of the blood culture vials be cleansed with iodine or alcohol before puncturing.9 If iodine is used, it should be allowed to remain in contact with the stopper for at least 30 seconds and then removed with an alcohol pad, as iodine can deteriorate the rubber stopper during incubation. For patients who may be allergic to iodine compounds, chlorhexidine solutions have been show to be exceptionally bactericidal.1,7 Some facilities gently scrub the site with an antibacterial soap, such as
Hibiclens. At least one phlebotomy textbook recommends swabbing with a second alcohol prep.8 I am not aware of any alcohol-only kits. 

Dennis J. Ernst
MT(ASCP)

Director
The Center for Phlebotomy Education
Ramsey, IN

References 

1. Frei R, Windmer A. Manual of Clinical Microbiology, 7th ed. Washington, DC. ASM Press. 1999. 

2. Weinbaum FI, Lavie S, Danek M, Sixsmith D, Heinrich G, Mills S. Doing it right the first time. Quality improvement and the contaminant blood culture. J Clin Micro. 1997;35(9):563-565. 

3. Schifman R, Pindur A. The effect of skin disinfection material on reducing blood culture contamination. Am J Clin
Pathol. 1993;99:536-538. 

4. Strand C, Wajsbort R, Sturman K. Effect of iodophor vs. tincture skin preparation on blood culture contamination rate.
JAMA. 1993;269(8):1004-1006. 

5. Little J, Murray P. Traynor P. Spitznagel E. A randomized trial of
povidone-iodine compared with iodine tincture for venipuncture site
disinfection: effects on rates of blood culture contamination. Am J Med 1999;107(2):119-125. 

6. Rohitkumar V, McGarr P, Draper M, Odell C. Strategies to reduce neonatal blood culture contamination rates. Am Ac
Pediatr. 1999;104(3):746. 

7. Mimoz O, Karim A, Mercat A, et al. Chlorhexidine compared with
povidone-iodine as skin Preparation before blood culture: a randomized controlled trial. Annals of Internal Medicine. 1999;131(11):834-837. 

8. Becan-McBride K, Garza D, Phlebotomy Handbook. Stamford, CT: Appleton & Lange; 1999. 

9. National Committee for Clinical Laboratory Standards. Procedures for the Collection of Diagnostic Blood Specimens by
Venipuncture. Approved Standard, H3-A4, Villanova, Pa, 1998. 

Contaminated urine cultures

Q: Our micro lab has a high rate of contaminated clean catch urine cultures (approximately 30 percent). We are addressing this problem with nursing. We would like to know if any studies have been done to determine the percentages for contaminated urines in hospitals nationwide. It would help us to know if our figures are average or unusually high.

A: Many factors affect the contamination rate for urine cultures, but a rate of 30 percent is at the high end of the values reported in the literature. Contaminated clean catch urine cultures are the result of poor specimen collection and/or prolonged transport time. While there is nearly universal agreement that contaminated urine cultures negatively impact patient care and increase costs, there is less agreement on the definition of contamination, the average rate of urine contamination, and measures to reduce the contamination rate.

Valenstein and Meier examined the frequency and causes of urine culture contamination in outpatients in the U.S.1 The median contamination rate was 18.1 percent. The top 10 percent of institutions reported that 5.6 percent or fewer urine cultures were contaminated, and the bottom 10 percent reported that 36.8 percent or more urine cultures were contaminated. As you would expect, the contamination rate in females (22.8 percent) was double the rate in males (11.2 percent). Other studies in the literature report a contamination rate that ranges from 2 percent to 31 percent. 

The key to obtaining an acceptable average rate of contamination rests on the definition of contaminated and significant urine culture.2 Valenstein and Meier defined a contaminated urine culture as one in which the culture yielded at least 10,000
CFU/mL of two or more different organisms.1 Others have defined a significant urine culture as the isolation of a uropathogen in > 100,000
CFU/mL in asymptomatic women, as > 1,000 CFU/mL in symptomatic men, or as > 1000
CFU/mL of E. coli, S. saprophyticus, Proteus spp, or Enterococcus
spp. in young symptomatic women. As an added complication, culture results are affected by the collection/transportation methods. Therefore, to monitor urine contamination rates as a QA indicator, the definition of contamination must be based on your patient population (e.g. percentage of males and females), urine collection methods, and methods of transportation. Most importantly, it should reflect what you hope to accomplish by monitoring urine contamination rates.

One solution to the problem of contaminated urine cultures is to have clean catch urine specimens collected by trained personnel.3 Otherwise, one should expect that a portion of urine specimens would be poorly collected. Also, the laboratory must enforce a policy that ensures the use of urine preservative or refrigeration temperatures during transportation of the specimen to the laboratory.

David Sewell, PhD, ABMM
Director of Microbiology
Veterans Affairs Medical Center
Portland, OR

Reference

1. Valenstein P and Meier F. Urine culture contamination: a College of American Pathologists Q-Probes study of contaminated urine cultures in 906 institutions. Arch Pathol Lab Med. 122:123-129, 1998.

2. Washington, JA. Urine culture contamination. Arch Pathol Lab Med. 122:120-122, 1998.

3. Pfau A.
Bacteriuria-sampling methods and significance. Infection 22(suppl):S42-S43, 1994. 

Daniel M. Baer is professor emeritus of laboratory medicine at Oregon Health Sciences University in Portland, OR, and a member of MLOs editorial advisory board.

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2002 Nelson Publishing, Inc. All rights reserved.

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