Variables affecting the quantitation of CD22 in neoplastic B cells.
BACKGROUND
Quantitative flow cytometry (QFCM) is being applied in the clinical flow cytometry laboratory for diagnosis, prognosis, and assessment of patients receiving antibody-based therapy. ABC values and the effect of technical variables on CD22 quantitation in acute lymphoblastic leukemia (ALL), chronic lymphocytic leukemia (CLL), mantle cell lymphoma (MCL), follicular lymphoma (FCL), hairy cell leukemia (HCL) and normal B cells were studied.


METHODS
The QuantiBrite System® was used to determine the level of CD22 expression (mean antibody bound per cell, ABC) by malignant and normal B cells. The intra-assay variability, number of cells required for precision, effect of delayed processing as well as shipment of peripheral blood specimens (delayed processing and exposure to noncontrolled environments), and the effect of paraformaldehyde fixation on assay results were studied.


RESULTS
The QuantiBRITE method of measuring CD22 ABC is precise (median CV 1.6%, 95% confidence interval, 1.2-2.3%) but a threshold of 250 malignant cells is required for reliable CD22 ABC values. Delayed processing and overnight shipment of specimens resulted in significantly different ABC values whereas fixation for up to 12 h had no significant effect. ABC measurements determined that CD22 expression is lower than normal in ALL, CLL, FCL, and MCL but higher than normal in HCL.


CONCLUSIONS
CD22 expression was atypical in the hematolymphoid malignancies studied and may have diagnostic utility. Technical variables such as cell number analyzed and delayed processing or overnight shipment of specimens impact significantly on the measurement of antigen expression by QFCM in the clinical laboratory.
Jasper
Gregory A
GA
Flow Cytometry Unit, Laboratory of Pathology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
Arun
Indu
I
Venzon
David
D
Kreitman
Robert J
RJ
Wayne
Alan S
AS
Yuan
Constance M
CM
Marti
Gerald E
GE
Stetler-Stevenson
Maryalice
M
D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D049109:Cell Proliferation; D005434:Flow Cytometry; D006801:Humans; D007943:Leukemia, Hairy Cell / Q000175:diagnosis / Q000276:immunology / Q000378:metabolism*; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000175:diagnosis / Q000276:immunology / Q000378:metabolism*; D008224:Lymphoma, Follicular / Q000175:diagnosis* / Q000276:immunology / Q000378:metabolism*; D020522:Lymphoma, Mantle-Cell / Q000175:diagnosis / Q000276:immunology / Q000378:metabolism*; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000175:diagnosis / Q000276:immunology / Q000378:metabolism*; D051918:Sialic Acid Binding Ig-like Lectin 2 / Q000032:analysis* / Q000096:biosynthesis / Q000276:immunology
D051918:Sialic Acid Binding Ig-like Lectin 2