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.

Band neutrophils, Differential leukocyte count, Left shift flag, Routine laboratory,
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