Editor’s note: This month, MLO’s clinical expert is Anthony Kurec, MS, H(ASCP)DLM. A New Yorker, Mr. Kurec has had a distinguished career as a laboratory technician, laboratory supervisor, administrator, and educator, has authored or co-authored more than 100 publications, and served as a director and officer of the Clinical Laboratory Management Association (CLMA).
Q I would like to ask questions about atypical lymphocytes in infants and children who are less than 10 years old. Our pathologist said we should not report atypical lymphocytes in infants (for example, 7 days old) and children because normal lymphocytes in these patients look similar to atypical lymphocytes.
Do we ever find atypical lymphocytes in these patients? If so, what are their characteristics or appearance?
A Infants and young children have a dynamic immune system as supported by the presence of an increased number of lymphocytes at birth (around 5.5 x 109/L), which remains for the first four years of life. Between the ages of 8 and 10 years, the number approaches that of an adult. Atypical lymphocytes may be present in normal, healthy adults (6% to 12%) and at slightly higher numbers in children. Because infants and children are building their repertoire of antibodies through exposure to a large variety of antigens, it would not be unusual to observe a small number of atypical lymphocytes in a child’s peripheral blood smear. These atypical lymphocytes morphologically appear the same as those found in adults.
Atypical lymphocytes, or “variant” lymphocytes as they are currently referred to, are defined as non-malignant lymphocytes that are in response to non-specific hematopoietic stress as seen with various conditions/disorders. Immunizations, viral infections, and hypersensitivity responses (drug reactions, insect bites) may be sources of such stress. In general, a white blood cell differential showing greater than 20% variant lymphocytes would be reportable and might require further examination.
Ultimately, it is the laboratory director’s responsibility to set reference parameters in making such determinations. Studies have shown that there is poor concordance among individuals in the accurate identification of variant lymphocytes; thus proper training is necessary to ensure consistency in identification and reporting. A written protocol that has been approved by your pathologist provides a good guide for staff in determining the kind of blood smear they wish to review and what they want reported.
In most cases the presence of variant lymphocytes is self-limiting and is resolved with improvement of the patient’s condition. However, in today’s litigious environment, clinicians may feel compelled to order additional (and expensive) tests when faced with an “abnormal” report. One additional point is that it is not uncommon for patients to request access to medical records. To the medically untrained, a report that declares anything “atypical” creates significant apprehension, especially for parents of a newborn or child. Though medically the report may be of minimal consequence, demanding parents can be a formidable force for any clinician. Thus laboratory professionals need to be well trained so they may best assist in providing a balanced view of what is clinically significant and what should be appropriately reported.
–Anthony Kurec, MS, H(ASCP)DLM
Clinical Associate Professor, Emeritus
SUNY Upstate Medical University
Syracuse, NY
For More Information
Kaushansky K, Lichtman MA, Beutler E, Kipp TJ, Prachal JT, Seligsohn U, eds. William’s Hematology. 8th ed. Chapters 2, 6, 81. McGraw-Hill: New York; 2010.
Koepke JA. Atypical lymphocytes: tips from the clinical experts. MLO. 2004;36(11):36.
Meer, Wim van der. Blood Cell Morphology: Controversies and Alternatives. Chapter 5. Radboud University: The Netherlands; 2006.
Wood TA, Frenkel EP. The atypical lymphocyte. Am J Med. 42(6):923-936.
MLO’s “Tips from the clinical experts” column provides practical, up-to-date solutions to readers’ technical and clinical issues from experts in various fields. Readers may send questions to [email protected].
