Answering your questions: critical value for bands, venipunctures in infants, dysmorphic red cells in urine and stability of pre-transfusion samples. (Tips from the Clinical Experts).
Q Several years ago, at the request a geriatric specialist, our lab designated >20 percent bands as a critical value. Thousands of phone calls to physicians later, we feel the need to drop this from our "critical call" list. We have been unable to justify continuing to use this criterion. Are we missing something?
A Neutrophilic responses can be a 1. useful indicator of infection and/or acute inflammation. (1) Some years ago, we decided to investigate the clinical value for careful identification of band or stab neutrophils. One of my graduate students did a careful evaluation of this information. Band counts greater than 6 percent were associated with early indications of infections and! or acute inflammatory states in the great majority of patients with normal total leukocyte counts. Our initial study group was composed of older patients. (2) Further studies indicated that pediatric patients also showed this association, but others have not agreed with this conclusion. (3)
Your action limit of >20 percent bands is much higher than the one we proposed, which may be due to differences in the criteria you are using for the identification of bands. Or if, indeed, there is no disagreement, your limits should have at least some clinical usefulness, since almost all patients with a >20 percent band count would have very obvious problems, and the blood count would have added little. If you do laboratory work for an acute care unit, such as a trauma center, perhaps the clinicians do not really need the calls since "everybody" is acutely ill.
On the other hand, if you lowered the alert call to >6 percent, the number of calls which you would make would undoubtedly increase -- unless you only call if there are >6 percent bands with a normal WBC. It should be added that after a left-shift alert has been called on a patient, any following ones need not be called again, since the clinician would already be aware of this information.
It is, however, very important that the clinicians are aware of the criteria being used to indicate a "left shift," and all laboratories in an institution must be checked to make sure they are using similar criteria to identify these cells. Our surgeons and pediatricians, in particular, were pleased with our program.
Over the years, there has been a continual uneasiness with the identification of bands. (4) With the development of flow cytometric hematology analyzers, the early morphologic criteria became, for the most part, impractical. Currently, there is a move to have the "left-shift" cells grouped into an immature granulocyte category. Which of the immature granulocytes would be included? This is currently under discussion as morphologic criteria become problematic when seeking to calibrate and control the quality of these instruments.
In every laboratory, a number of steps should be taken to confirm these views. First, the accuracy of segmented/stab neutrophil differentiation of the technologists must be standardized. Then, a normal value study should be done to determine the upper level of normal for band cells in your patient population. Finally, the clinical pathologists should meet with the clinicians to determine which "alert-/critical-call values" should be called to the doctors.
I remain a believer in the value of a carefully done differential count, but standardizing this determination has been a monumental task. Currently, the determination of "immature granulocytes" seems to be where we are heading. (5) Also, with the increasing availability of hematology analyzers, which report the differential count in absolute terms, we should all move in that direction for our reporting. This obviates a significant amount of confusion in the interpretation of the proportional differential counts.
John A. Koepke, MD
Professor Emeritus of Pathology Duke University Medicai Center
(1.) Boggs DR. Response of blood leukocytes to common stimuli. In, Differential Leukecyte Counting, JA Koepke, ed. Collage of American Pathologists, 1978
(2.) Mathy KA, Koepke JA. The clinical usefulness of segemented vs. stab neutrephil criteria for differential leukocyte Counts. Am J Clin Pathol. 1974;61:917-958.
(3.) Andron MJ, Westengard JC, Dutcher TF. Band neutrophil counts are unnecessary for the diagnosis of infection in patients with normal total leukocyte counts. Am J Clin Pathol. 1994:192:646-649.
(4.) Cornbleet PJ, Novak RW. Lack of reproducibility of band neutrophil identification despite the use of uniform identification criteria. Lab Hematol. 1995;1:89-96.
(5.) Koepke JA. How should neutrophil reactions be measured? [editorial] Lab Hematol. 1995;1:87-88
Venipunctures in infants
Q I have a question related to phlebotomy procedures on infants in the hospital nursery. Our phlebotomy staff has been told by the nursery RNs that they must use syringes to draw blood, based on the fact that the vacuum in the tubes damages the veins. Do you have any information or studies that prove/disprove this statement?
A Although the nursery RNs are correct about using only syringes for newborn venipunctures, their rational is questionable. Using an evacuated tube/tube holder system to draw from the small veins that newborns present significantly diminishes the chances of a successful venipuncture. Because newborn veins are so small, they are likely to collapse when the vacuum of the tube is applied. Syringes, on the other hand, allow the collector to control the amount of vacuum applied to the interior of the vein and minimize the potential for collapse and hemolysis. While the nurses' advice to use syringes is good in that it increases the chances of a successful venipuncture, one is hard-pressed to find evidence in the literature that the vacuum in tubes, if applied directly, damages veins. It is conceivable but not documented, to my knowledge.
-- Dennis Ernst, MT(ASCP)
The Center for Phlebotomy Education Inc.
Dysmorphic red cells in urine
Q What is the importance of reporting dysmorphic and isomorphic red cells in urine? How are they quantitated? One of our renal-care physicians would like for us to begin reporting these sightings.
A The presence of dysmorphic red A cells in the urine sediment is generally felt to indicate glomerular bleeding (or glomerular involvement), such as is seen with glomerulonephritis. Dysmorphic red cells are abnormally shaped or distorted. It is felt that they become bent, distorted or twisted with loss of cell membrane as they pass through the glomerulus. They have also been described as having cytoplasmic blebs or "Mickey Mouse ears." They are best visualized using phase-contrast microscopy. Birch and Fairley described the association of dysmorphic red cells with glomerular bleeding and isomorphic (morphologically uniform) red cells as nonglomerular in 1983. (1) Others have confirmed their results. The indication of glomerular involvement is enhanced when dysmorphic red cells are accompanied by findings such as proteinuria and the presence of casts, especially red-cell casts, in the urine sediment.
Very rarely, other abnormally shaped red cells (also referred to as dysmorphic) -- but not associated with glomerular involvement -- have been seen in the urine sediment. These include nucleated red cells, sickle cells and other poikilocytes.
As to quantification of dysmorphic red cells, I am unaware of a standard protocol.
We grade the presence of red cells according to our laboratory protocol, and include a comment that dysmorphic red cells are present. Protocol for further quantitation should be determined for your institution. For example, you might report dysmorphic forms as being few, moderate or many, or the percentage of dysmorphic forms per total red cells present might be estimated.
-- Karen M. Ringsrud MT(ASCP)
Department of Laboratory Medicine and Pathology
University of Minnesota Medical School
(1.) Birch DF, Fairley KF, et al. Clin Nephrol. 1983 Aug;20(2): 78-84
Stability of pre-transfusion samples
Q Is there a written standard that addresses how long a recipient blood sample can remain unrefrigerated before it must be rejected for pre-transfusion testing?
A To be in compliance with CLIA, AABB and CAP standards, laboratories should have a policy that defines appropriate pre-analytic specimen handling (typically documented in sample suitability section of laboratory procedure manual). The precise details of appropriate pre-analytical handling are left to the discretion of the testing laboratory.
AABB standard 5.1.8 (1) states: "The blood bank or transfusion service shall have a process to ensure that blood, components, samples and critical materials are handled, stored, distributed and transported in a manner that prevents damage, limits deterioration and ... meets criteria for storage, transportation and expiration." AABB criteria (Chart 5.1.8A) do not spell out specific time or temperature standards for the transportation of pre-transfusion samples.
CAP inspection item TRM.4000 (2) states that typing sera must be used according to the manufacturers' instructions. The product inserts of two major manufacturers state that samples should/must be refrigerated at 2[degrees] to -8[degrees]C if testing cannot be performed "promptly." When contacted, neither manufacturer was able to precisely define the term. De facto, the laboratory needs to make its own definition of "promptly."
The primary concern with unrefrigerated, pre-transfusion specimens is that room-temperature storage promotes bacterial proliferation. Another concern is that temperature extremes during prolonged shipment might degrade specimen integrity. Either condition could interfere with testing. Defining the acceptable interval for unrefrigerated specimens at 24 hours is a common practice (personal observation). Hospitals in warmer climates may elect to use a shorter interval because of temperature-related specimen degradation. The product inserts set an upper limit of two days, by instructing that testing must be completed within 48 hours (an FDA requirement currently under review (3)). The laboratory should check the product inserts to ensure that their practices do not violate their manufacturers' instructions.
-- Richard M. Scanlan, MD
Co-Director Transfusion Medicine
Oregon Health & Science University
(1.) Standards for Bleed Banks and Transfusion Services 20th Edition AABB 2000.
(2.) Transfusion Medicine Checklist, College of American Pathologists 2001
(3.) Recipient Serum Samples -- CBER memorandum 4/6/94. Available at: http://www.fda.gov/cber/bldmem/040694.pdf.
Daniel M. Baer is professor emeritus of laboratory medicine at Oregon Health and Science University in Portland, OR, end a member of MLO's editorial advisory board.
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|Author:||Baer, Daniel M.|
|Publication:||Medical Laboratory Observer|
|Date:||May 1, 2003|
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