title: Left Shift 1+ flag for the detection of band neutrophils: interlaboratory variations and recommendations for the routine laboratory.
abstract: BACKGROUND
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Clinical Chemistry, Maasstad Ziekenhuis, Rotterdam, The Netherlands.
authors.forename: F
authors.initials: F
authors.lastname: Weerkamp
authors.forename: P H
authors.initials: PH
authors.lastname: Taal
authors.forename: B A
authors.initials: BA
authors.lastname: De Boer
mesh_terms: D057205:Automation, Laboratory / Q000295:instrumentation / Q000379:methods; D019411:Clinical Laboratory Techniques / Q000295:instrumentation* / Q000379:methods; D006403:Hematologic Tests / Q000295:instrumentation* / Q000379:methods; D006801:Humans; D007755:Laboratories, Hospital; D007958:Leukocyte Count / Q000295:instrumentation / Q000379:methods; D009504:Neutrophils / Q000166:cytology*; D015203:Reproducibility of Results