title: Evaluation of hematocrit bias on blood glucose measurement with six different portable glucose meters.
abstract: BACKGROUND
  Measurement and monitoring of blood glucose levels in hospitalized patients with portable glucose meters (PGMs) is performed widely and is an essential part of diabetes monitoring, despite the increasing evidence of several interferences which can negatively bias the accuracy of measurements. The purpose of this study was to evaluate the effect of the hematocrit on the analytical performances of different PGMs as compared with a reference laboratory assay.
  
  
  METHODS
  The effect of various hematocrit values (approximiately 0.20, approximiately 0.45 and approximiately 0.63 L/L) were assessed in three whole blood specimens with different glucose concentration (approximiately 1.1, approximiately 13.3, and approximiately 25 mmol/L) by using six different commercial PGMs. The identical samples were also tested with the laboratory reference assay (i.e., hexokinase). The percentage difference from the laboratory assay (%Diff) was calculated as follows: % Diff = average PGM value - value from laboratory assay x 100 / value from laboratory assay.
  
  
  RESULTS
  The %Diff of the six different PGMs were rather broad, and comprised between 56.5% and -34.8% in the sample with low glucose concentration (approximiately 1.1 mmol/L), between 40% and -32% in the sample with high glucose concentration (approximiately 13.3 mmol/L), and between -50% and 15% in the sample with very high glucose concentration (approximiately 25 mmol/L), respectively. It is also noteworthy that a very high hematocrit value (up to 0.63 L/L) generated a remarkable negative bias in blood glucose (-35%) as measured with the laboratory assay, when compared with the reference sample (hematocrit 0.45 L/L).
  
  
  CONCLUSIONS
  The results of this analytical evaluation clearly confirm that hematocrit produces a strong and almost unpredictable bias on PGMs performances, which is mainly dependent on the different type of devices. As such, the healthcare staff and the patients must be aware of this limitation, especially in the presence of extreme hematocrit levels, when plasma glucose assessment with the reference laboratory technique might be advisable.
authors.affiliation: Clinical Biochemical Laboratory, Regional Hospital of Bolzano, Italy. massimo.daves@asbz.it
authors.forename: Massimo
authors.initials: M
authors.lastname: Daves
authors.forename: Roberto
authors.initials: R
authors.lastname: Cemin
authors.forename: Bruno
authors.initials: B
authors.lastname: Fattor
authors.forename: Giovanni
authors.initials: G
authors.lastname: Cosio
authors.forename: Gian Luca
authors.initials: GL
authors.lastname: Salvagno
authors.forename: Francesco
authors.initials: F
authors.lastname: Rizza
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Lippi
mesh_terms: D015982:Bias; D001786:Blood Glucose / Q000032:analysis*; D015190:Blood Glucose Self-Monitoring / Q000295:instrumentation / Q000379:methods / Q000592:standards / Q000706:statistics & numerical data; D001800:Blood Specimen Collection / Q000295:instrumentation / Q000379:methods / Q000592:standards; D003920:Diabetes Mellitus / Q000097:blood* / Q000628:therapy; D004864:Equipment and Supplies / Q000706:statistics & numerical data; D006400:Hematocrit / Q000592:standards; D006760:Hospitalization; D006801:Humans; D008991:Monitoring, Physiologic / Q000295:instrumentation* / Q000379:methods / Q000592:standards / Q000706:statistics & numerical data; D009994:Osmolar Concentration; D011237:Predictive Value of Tests; D015203:Reproducibility of Results
chemical_list: D001786:Blood Glucose