Establishing Absolute Lymphocyte Count Thresholds for Further Review of Peripheral Blood Lymphocytosis to Judiciously Screen for Monoclonal B-Cell Populations in Older Adults

• Published in: American journal of clinical pathology 2019-09, Vol.152 (4), p.458-462
• Main Authors: Muscara, Matthew J, Cook, Benjamin A, Dhesi, Mary S, Groo, Stephen C, Andrews, Jared M
• Format: Article
• Language: English
• Subjects: Aged; Aged, 80 and over; B-Lymphocytes; Blood cell count; Care and treatment; Cell number; Development and progression; Diagnosis; Diagnosis, Differential; Female; Flow cytometry; Humans; Lymphatic diseases; Lymphocyte Count; Lymphocytes; Lymphocytes B; Lymphocytosis; Lymphocytosis - blood; Lymphocytosis - diagnosis; Lymphoproliferative disorders; Lymphoproliferative Disorders - blood; Lymphoproliferative Disorders - diagnosis; Male; Medical research; Medicine, Experimental; Middle Aged; Peripheral blood; Testing
• ISSN: 0002-9173; 1943-7722
• DOI: 10.1093/ajcp/aqz057

Abstract Objectives Lymphocytosis may represent either a lymphoproliferative disorder (LPD) or a reactive process. The absolute lymphocyte count (ALC) threshold for further evaluation of lymphocytosis is not well established. Methods We prospectively performed flow cytometry on blood samples from patients 50 years or older with ALCs of 4.0 × 109 cells/L or greater without a history of an LPD. Results Monoclonal B-cell populations were found in 34 (19.1%) of 178 cases, with incidence increasing with age. In patients younger than 75 years, no monoclonal B-cell population was identified in patients with ALCs less than 4.4 × 109 cells/L, while such clones were found below and above this threshold in patients 75 years and older. Conclusions These findings support a threshold for smear review and flow cytometry no lower than 4.4 × 109 cells/L in patients younger than 75 years and a threshold as low as 4.0 × 109 cells/L in patients 75 years and older.