Lipemia and the CBC, immunohematology results

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Q: What CBC parameters are affected when the specimen is lipemic?

A: Lipemia in a blood specimen used for clinical evaluation can cause significant interference with obtaining accurate test values. Lipemia creates turbidity of a sample and is a result of the accumulation of lipid particles. Highdensity lipoproteins (HDL) range in size from 6–12.5 nm, low-density lipoproteins (LDL) range from 20–26 nm, very low- density particles range from 27–200 nm, and chylomicrons from 70–1,000 nm.¹

The turbidity seen in lipemia is mainly due to the presence of chylomicrons. These large particles create light scatter, resulting in elevated absorbance levels that impact colorimetric determinations.² Classical physics tells us that the amount of absorbed light is inversely proportional to the wavelength. Thus any methodology that employs low-end wavelengths as part of the analysis process would be affected.

In addition, the accumulation of these large particles can create volume displacement, causing pseudo-hyponatremia.1,2 Normal plasma is 92 percent water and 8 percent lipids. Lipemia can displace this ratio by falsely increasing the lipid proportion to as much 25 percent of the total plasma/serum volume.² Many clinical analytes are found in the aqueous layer of plasma/serum, thus decreasing certain test values in lipemic specimens, while lipid-soluble analytes may be erroneously elevated.³

Most hematology analyzers use spectrophometric analysis when measuring hemoglobin levels. Turbidity can falsely elevate a hemoglobin level and thus result in miscalculating RBC indices (MCH and MCHC). It has also been reported that lipemic specimens analyzed on optical hematology instruments may also erroneously impact white blood cells counts (WBC) and platelet counts.^2,4

Lipemia most often results from specimens collected soon after an individual has had a particularly fatty meal. Certain disorders (multiple myeloma, diabetes mellitus, acute pancreatitis, kidney failure, or hypothyreosis) may also contribute to lipemia, as do certain drugs (such as L-asparaginase) with a fat emulsion base.^1,4,5

Lipemic specimens can easily be identified if the blood is centrifuged or sits for a period of time, allowing for the natural gravitational separation of cells and plasma, of which the latter is visibly turbid. While it is impractical to visually observe each specimen submitted for the presence of lipemia, one may become aware if certain parameters do not “appear” to be correct, i.e., hematocrit is not roughly three times that of the hemoglobin and/or the mean corpuscular hemoglobin concentration (MCHC) is greater than 36. Those instruments that produce scattergrams may also be a source for review in identifying potential errors within the CBC.⁴

Each laboratory must establish an appropriate policy and procedure to address such situations and provide corrective measures.⁶ This should include clear instructions to patients regarding the laboratory’s fasting protocol (fasting eight to 12 hours before the draw) when appropriate. However, when acute lipemic specimens are received, each laboratory must decide what standard practice(s) needs to be in place depending on the methodology used.⁷
—Anthony Kurec, MS, H(ASCP)DLM

References

1. Nikolac N. Lipemia: causes, interference mechanisms, detection, and management. Biochemia Medica.2014;24(1):57–67.
2. Kroll MH, Elin RJ. Interference with clinical laborator analyses. Clin Chem. 1994;40(11):1996-2005.
3. Roche Diagnostics. Serum indices: Reduction of clinical errors in laboratory medicine. 2007. http://roche-diagnostics.cz/Products/Documents/PD/Spolecne/Serove_indexy.pdf. Accessed January 25, 2016.
4. Zandecki M, Genevieve F, Gerad J, Godon A. Spurious counts and spurious results on haematology analysers: A review. Part I: platelets. Intl J Lab Hematol. 2007; 29(4):4-20.
5. Zandecki M, Genevieve F, Gerad J, Godon A. Spurious counts and spurious results on haematology analysers: A review. Part II: White blood cells, red blood cells, haemoglobin, red cell indices and reticulocytes. Intl J Lab Hematol. 2007; 29(4):21-41.
6. College of American Pathologists. Hemolyzed or Lipemic Specimens—CBC CAP Hematology and Coagulation Checklist. HEM 22200.
7. Savage RA. CAP Today, July 2004. College of American Pathologists. http://www.captodayonline.com/Archives/q_and_a/qa_07_04.html. Accessed January 25, 2016.

Q: Can you provide examples for intermediate test results for Immunohematology for manual testing? The six methods for evaluating competency assessment are written to fit other areas of the lab. Can you provide recommendations for evaluating the Transfusion Service?

A: The third of the six procedures required by CLIA  (42 CFR 493.1235 and 493.1451) to be used for assessing the competency of testing personnel is “Review of intermediate test results or worksheets, quality control records, proficiency testing results, and preventive maintenance records.” Blood bank tests are made up of reactions that are often graded by strength and a conclusion made from those results. For example, Anti-A = 4+, Anti-B = Neg, Anti-D = 4+, A cells = Neg, B cells = 4+ leads to the conclusion of Group A, Rh Positive. The graded tests results are the intermediate test results. The conclusion of Group A, Rh Positive is based on these intermediate results. The same is true if the results were simply recorded as positive and negative rather than the positive results being scored. There are results and a conclusion drawn from the results. The results and the conclusions of ABO and Rh, antibody screening, antibody identification panels, crossmatches, and fetomaternal hemorrhage screening results and conclusions could all be reviewed in a manual system.
—Suzanne H. Butch, MA, MLS(ASCP)^CM, SBB^CM, DLM^CM, CQA(ASQ)

Editor’s Note: Anthony Kurec, MS,H(ASCP)DLM, is Clinical Associate Professor, Emeritus, at SUNY Upstate Medical University in Syracuse, NY.
Suzanne H. Butch, MA, MLS(ASCP)CM,SBBCM, DLMCM, CQA(ASQ), serves as Compliance Manager for the Department of Pathology and Administrative Manager for the Blood Bank and Transfusion Service of the University of Michigan Hospitals and Health Centers, Ann Arbor, Michigan.
Both are also members of the MLO Editorial Advisory Board.