Q
When preheating a specimen with a severe cold agglutinin does not work (i.e., MCHC remains > 37.0), what is the best way to tackle this problem? Replacing plasma with warm saline, running it, and recalculating the affected parameters has been suggested.
A
When we have encountered a patient with a cold agglutinin and re-warming the sample does not correct the problem, we have employed a technique of replacing the plasma with warm isotonic diluent used by our analyzers. We have Sysmex analyzers and this method is suggested in the company’s troubleshooting guide. Blood banks employ warm saline washes to remove the circulating antibody that coats the RBCs when cross-matching blood for patients with cold agglutinins. The concept is the same when trying to obtain valid CBC results.
—Donna L. Canterbury, MT (ASCP)SH
Hematology Supervisor–Core Laboratory
University of Virginia Health Systems
Q
I would like to know if there is any reason why we shouldn’t use patient labels on urine instrument tapes. Also, would there be any cautions such as where to put them? For example, our instrument prints out the information and patient ID # at the top. Is there any reason we shouldn’t cover that information? The patient number is typed in on a number pad before it is dipped by the tech running tech and is typically labeled by the same tech. We are using the Clinitek Stratus.
A
We use the Siemens Clinitek Status instrument. Our instruments have connectivity to the Siemens middleware RapidCOMM 4.0. Operators enter the 10-digit billing ID manually or via barcode scanner, and the patient results upload to our laboratory information system and then into the EMR (EPIC). We are aware that some locations will place the patient’s label on the print-out which they give to the physician. Following the review, the print-outs are then placed in a designated bin for paperwork containing PHI (the contents of the bins are shredded). It is a good practice not to cover up the MRN on the print-out in case there is a question, particularly if you are saving these print-outs.
—Denise Eavers, MPH, MT (ASCP),
Manager, Point of Care Testing,
University of Virginia Health System Medical Laboratories
Q
How does one correct a hemoglobin determination when a patient presents with grossly lipemic plasma/serum?
A
Interference with routine hemoglobin determinations may be suspected when the MCH and/or MCHC appear unlikely and can occur when lipid levels are elevated (lipemia). The difference between this type of interference and other types, such as hemolysis or icterus, is that lipemic specimens consist of suspended particles of VLDL (very low density lipoproteins) and chylomicrons, causing varying degrees of turbidity.1,2 This turbidity is a direct result of the presence of large lipid particles which increase absorbance and light scatter.
The physics behind turbidity and its interfering qualities can be complex. The suspended particles, when subjected to electromagnetic radiation (i.e., light), create a dipole environment that is proportional to the strength of the electric field and the polarizing capacity of the particles.2 This polarization of the particles is known as Rayleigh scattering, causing particle oscillation at the same frequency as the light wavelength. This results in a scattering effect and is related to the number and size of the particles. VLDL particles vary in size, from 27 nm to 200 nm, and chylomicrons vary from 70 to 1,000 nm.2
Beer’s law states that the absorbance (A) of monochromatic light by a solution is proportional to the absorptivity (a), the light path length (b), and the concentration (c); i.e., A = abc. Thus, the intensity of the transmitted light becomes more diminished in a lipemic patient’s hemoglobin sample due to the reflecting or absorbing of some of the transmitted light, ultimately rendering a false hemoglobin value. The Rayleigh effect applies as long as the particle size remains smaller than the wavelength of the light. As particles increase in size, a secondary effect, Mie scattering, occurs, adding to the complexity of this process.
The presence of lipemia is generally determined by directly observing the patient’s plasma post centrifugation and/or questioning the MCHC value (>36.5). Review of the patient’s peripheral blood smear will also show fuzzy red cell outlines. To correct for the presence of lipemia, a microhematocrit is performed and a blank from the patient’s lipemic plasma is prepared. The following adjustment can then be made:3
True Hgb = measured Hgb – [Hgb of patient’s lipemic plasma sample x (1 – microhematocrit)]
An alternative to this is to remove the lipemic plasma and add an equal amount of isotonic solution, which then allows for standard processing.3 The newly obtained MCHC times the microhematocrit divided by 100 will render the true hemoglobin concentration. It has also been reported that using a modified hemoglobin reagent, tri-methyl-tetra-decyl-ammonium chloride free (TTAB-free), can improve hemoglobin determinations of lipemic specimens.4
—Anthony Kurec, MS, H(ASCP)DLM
Clinical Associate Professor, Emeritus,
SUNY Upstate Medical University, Syracuse, NY
References
- Kroll MH. Evaluating interference caused by lipemia.Clin Chem.2004;50(1):1968-69.
- Kroll MH, Elin RJ. Interference with clinical laboratory analyses. Clin Chem.1994;40(11):1996-2005.
- Bain BJ. Detecting erroneous blood counts, in Blood Cells: A Practical Guide, 4th ed. (2006) Blackwell Publishing:London. P180.http://advancingyourlab.com/LP=204. Accessed January 17, 2014.
- Grimaldi E, Scopacasa F. Evaluation of the Abbott Cell-Dyn 4000 hematology analyzer. Am J Clin Pathol.2000;113:497-505.
