FLOW CYTOMETRIC RETICULOCYTE ANALYSIS - MULTIINSTITUTIONAL INTERLABORATORY CORRELATION STUDY

Reticulocyte analysis by flow cytometry offers precision and sensitivi ty greater than those of conventional morphologic methods and permits derivation of a reticulocyte maturity index. However, interlaboratory variability has not yet been reported. The authors analyzed 310 sample s at eight sites using 11 instruments over a 4-month period to examine intermethod and interlaboratory variabilities. Stains included thiazo le orange, ethidium bromide, and auramine O. Instruments included mode ls by Coulter, Becton Dickinson, TOA Medical Electronics, and Ortho Di agnostics. The coefficient of variation (CV) among all sites and metho ds on these samples varied as a function of the reticulocyte percentag e, ranging from a mean CV of 69% for samples with <.5% reticulocytes t o 24.1% for those with >2.5% reticulocytes. The best performance was o bserved with the TOA R-1000 dedicated reticulocyte analyzers, with a m ean CV of 18.4% for samples with <.5% reticulocytes and 4.6% for sampl es with >2.5% reticulocytes. The reticulocyte maturity index showed co mparable intersite precision, with a mean CV of 16% for samples with > 2.5% reticulocytes with multipurpose flow cytometers and a mean CV of 7.3% with the TOA R-1000 instruments. Interclass correlations among al l sites ranged from .79 to .99 for the reticulocyte counts and .41 to .88 for the reticulocyte maturity index. The authors conclude that flo w cytometric reticulocyte analysis is more precise than manual reticul ocyte analysis. With greater automation of this methodology, further i nterlaboratory standardization of reticulocyte counts and the reticulo cyte maturity index can be achieved.