title: Evaluation of the performance of a point-of-care method for total and differential white blood cell count in clozapine users.
abstract: BACKGROUND
  We evaluated the performance of the HemoCue WBC DIFF, a point-of-care device for total and differential white cell count, primarily to test its suitability for the mandatory white blood cell monitoring in clozapine use.
  
  
  METHODS
  Leukocyte count and 5-part differentiation was performed by the point-of-care device and by routine laboratory method in venous EDTA-blood samples from 20 clozapine users, 20 neutropenic patients, and 20 healthy volunteers. From the volunteers, also a capillary sample was drawn. Intra-assay reproducibility and drop-to-drop variation were tested.
  
  
  RESULTS
  The correlation between both methods in venous samples was r > 0.95 for leukocyte, neutrophil, and lymphocyte counts. The correlation between point-of-care (capillary sample) and routine (venous sample) methods for these cells was 0.772; 0.817 and 0.798, respectively. Only for leukocyte and neutrophil counts, the intra-assay reproducibility was sufficient.
  
  
  CONCLUSIONS
  The point-of-care device can be used to screen for leukocyte and neutrophil counts. Because of the relatively high measurement uncertainty and poor correlation with venous samples, we recommend to repeat the measurement with a venous sample if cell counts are in the lower reference range. In case of clozapine therapy, neutropenia can probably be excluded if high neutrophil counts are found and patients can continue their therapy.
authors: Atalmedial Medical Diagnostic Centers, Hoofddorp, The Netherlands.
authors: H N
authors: HN
authors: Bui
authors: Psychiatric Centre Rivierduinen, Oegstgeest, The Netherlands.
authors: J P A M
authors: JP
authors: Bogers
authors: Department of Community Mental Health, Mental Health Service North Holland North, Heerhugowaard, The Netherlands.
authors: D
authors: D
authors: Cohen
authors: Saltro Diagnostic Center for Primary Care, Utrecht, The Netherlands.
authors: T
authors: T
authors: Njo
authors: Atalmedial Medical Diagnostic Centers, Hoofddorp, The Netherlands.
authors: M H
authors: MH
authors: Herruer
mesh_terms: D014150:Antipsychotic Agents / Q000627:therapeutic use*; D016022:Case-Control Studies; D003024:Clozapine / Q000627:therapeutic use*; D016903:Drug Monitoring / Q000379:methods*; D006403:Hematologic Tests; D006801:Humans; D007958:Leukocyte Count; D009504:Neutrophils / Q000166:cytology; D019095:Point-of-Care Systems
chemical_list: D014150:Antipsychotic Agents; D003024:Clozapine
keywords: Point-of-care testing; WBC; clozapine; leukocytes; schizophrenia