Introduction: Microscopic differential analysis of leukocytes is a time-consuming activity for routine diagnostic laboratories. The criteria used to decide whether a manual differential should be performed should therefore be as strict as possible. The goal of this investigation was to give recommendations for the use of the left shift (LS) 1+ flag, which signals the presence of band neutrophils. Methods: The LS1+ flag of the ADVIA 120 and 2120 hematology analyzers was evaluated in 6 peripheral hospital laboratories in the Netherlands. In 2683 samples with exclusively a LS1+ flag, the percentage of band neutrophils were determined microscopically. A set of photographs of neutrophils were used to examine the differences between laboratories in the assessment of band cells. Results: In 18% of all samples with only a LS1+ flag, 5% or more band neutrophils were found. However, this percentage differed greatly between laboratories, as did the proportion of samples that received a LS1+ flag. Several factors were found to influence the amount and accuracy of the LS1+ alarm, i.e. band neutrophil counting by microscopists, specificity of request for leukocyte differentials, percentage of general practitioners requesting a leukocyte differential, and sample storage. Based on these findings, a number of recommendations were formulated. Conclusion:; Critical control of the factors influencing the LS1+ flag can significantly decrease the number of microscopic samples to be reviewed and may be valuable for every laboratory performing routine differentials, using any type of hematology analyzer.

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International Journal of Laboratory Hematology
Erasmus MC: University Medical Center Rotterdam

Weerkamp, F, Taal, P.H, & de Boer, B.A. (2011). Left Shift 1+ flag for the detection of band neutrophils: interlaboratory variations and recommendations for the routine laboratory. International Journal of Laboratory Hematology, 33(6), 601–609. doi:10.1111/j.1751-553X.2011.01340.x