Editor: Frederick L. Kiechle, MD, PhD
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Q. What are the requirements for correcting an automated white blood cell (WBC) count for the presence of megakaryocytes? Is there a formula for correcting it for megakaryocytes, as there is for the presence of nucleated red blood cells (nRBCs)?
A. June 2024—Per CAP checklist requirement HEM.30100 Detection/Correction Procedure—WBC, laboratories are required to have a process to detect and correct automated WBC counts for the presence of megakaryocytes or nRBCs. Automated hematology analyzers may incorrectly include megakaryocytes in the total WBC count, so the laboratory must evaluate its own system and develop appropriate corrective actions to eliminate megakaryocytes or megakaryocyte fragments from the total WBC count.
The procedure for manually correcting WBC counts for the presence of megakaryocytes is similar to that for nRBCs. The formula for correcting WBC counts for megakaryocytes and/or megakaryocyte fragments is: corrected WBC count = (automated uncorrected WBC count × 100) ÷ (100 + number of megakaryocytes or megakaryocyte fragments per 100 WBCs).
There is no uniform threshold for when to report a corrected WBC count, so each laboratory should define this number (for example, five megakaryocytes per 100 WBCs) in its protocol.
Circulating megakaryocytes are not a common cause of spuriously elevated WBC counts, but identifying the rare instances when they do cause elevated counts can have important implications for clinical management.
Brereton M, McCafferty R, Marsden K, Kawai Y, Etzell J, Ermens A; International Council for Standardization in Haematology. Recommendation for standardization of haematology reporting units used in the extended blood count. Int J Lab Hematol. 2016;38(5):472–482.
College of American Pathologists. HEM.30100 Detection/correction procedure—WBC. In: Hematology and coagulation checklist. Aug. 24, 2023.
Gulati G, Uppal G, Gong J. Unreliable automated complete blood count results: causes, recognition, and resolution. Ann Lab Med. 2022;42(5):515–530.
Philipp Raess, MD, PhD
Associate Professor
Department of Pathology and Laboratory Medicine
Oregon Health & Science University
Portland, Ore.
Vice Chair, CAP Hematology/Clinical Microscopy Committee
Q. Are there guidelines on how often a patient should be monitored for a blood transfusion reaction? Should reactions be monitored as frequently as vital signs?
A. To my knowledge, there are no professional guidelines for adults or children on how often to monitor patients for the duration of a transfusion. The College of American Pathologists transfusion medicine checklist addresses positive patient identification, transfusionist training, and blood administration records. The latter includes providing evidence of patient monitoring pretransfusion and during and after transfusion. However, the checklist does not address specific requirements about how often to monitor.
I have found numerous institution-specific transfusion administration guidelines, and they all have the same verbiage and the same reference to the Technical Manual. The manual chapter titled “Administration of blood components” states that vital signs must be taken within 15 minutes of beginning the transfusion, periodically during transfusion, and after transfusion. The timing and frequency of monitoring vital signs is often determined by institutional policy.
Transfusion reactions can occur at any point during or after transfusion. Ultimately, frequent patient monitoring during the transfusion is the best way for the transfusionist to be alerted to a possible transfusion reaction and allows for prompt intervention. Monitoring standards and guidelines for children and adults do not differ. Since institution-specific guidelines should be spelled out in an institutional policy, a multidisciplinary transfusion committee should be involved with developing and enforcing the policy to ensure that transfusions are conducted safely and efficiently.
Since this question was submitted by a reader in California, I would like to add that California state law requires following AABB standard 5.29.1, which states that the patient’s medical record shall include, among other information, the date and time of transfusion; vital signs taken at facility-defined intervals, including before, during, and after transfusion; and, if applicable, transfusion-related adverse events.
Association for the Advancement of Blood and Biotherapies. Standards for Blood Banks and Transfusion Services. 33rd ed. AABB Press; 2022.
Calif. HSC §1602.5 (d)(1) (1963).
College of American Pathologists. TRM.41025 Transfusionist training. In: Transfusion medicine checklist. Aug. 24, 2023.
College of American Pathologists. TRM.41450 Blood administration record. In: Transfusion medicine checklist. Aug. 24, 2023.
College of American Pathologists. TRM.41475 Post-transfusion observation. In: Transfusion medicine checklist. Aug. 24, 2023.
Jorgenson M. Administration of blood components. In: Cohn CS, Delaney M, Johnson ST, Katz LM, eds. Technical Manual. 20th ed. AABB Press; 2020.
Jay Hudgins, DO, MS
Director of Hemostasis and Thrombosis
Nationwide Children’s Hospital
Associate Professor of Clinical Pathology
Ohio State University College of Medicine
Columbus, Ohio
Former Member, CAP Transfusion, Apheresis, and Cellular Therapy Committee