title: Point and trend accuracy of a continuous intravenous microdialysis-based glucose-monitoring device in critically ill patients: a prospective study.
abstract: BACKGROUND
  Microdialysis is a well-established technology that can be used for continuous blood glucose monitoring. We determined point and trend accuracy, and reliability of a microdialysis-based continuous blood glucose-monitoring device (EIRUS(®)) in critically ill patients.
  
  
  METHODS
  Prospective study involving patients with an expected intensive care unit stay of ≥48 h. Every 15 min, device readings were compared with blood glucose values measured in arterial blood during blocks of 8 h per day for a maximum of 3 days. The Clarke error grid, Bland-Altman plot, mean absolute relative difference and glucose prediction error analysis were used to express point accuracy and the rate error grid to express trend accuracy. Reliability testing included aspects of the device and the external sensor, and the special central venous catheter (CVC) with a semipermeable membrane for use with this device.
  
  
  RESULTS
  We collected 594 paired values in 12 patients (65 [26-80; 8-97] (median [IQR; total range]) paired values per patient). Point accuracy: 93.6 % of paired values were in zone A of the Clarke error grid, 6.4 % were in zone B; bias was 4.1 mg/dL with an upper limit of agreement of 28.6 mg/dL and a lower level of agreement of -20.5 mg/dL in the Bland-Altman analysis; 93.6 % of the values ≥75 mg/dL were within 20 % of the reference values in the glucose prediction error analysis; the mean absolute relative difference was 7.5 %. Trend accuracy: 96.4 % of the paired values were in zone A, and 3.3 and 0.3 % were in zone B and zone C of the rate error grid. Reliability: out of 16 sensors, 4 had to be replaced prematurely; out of 12 CVCs, two malfunctioned (one after unintentional flushing by unsupervised nurses of the ports connected to the internal microdialysis chamber, causing rupture of the semipermeable membrane; one for an unknown reason). Device start-up time was 58 [56-67] min; availability of real-time data was 100 % of the connection time.
  
  
  CONCLUSIONS
  In this study in critically ill patients who had no hypoglycemic episodes and a limited number of hyperglycemic excursions, point accuracy of the device was moderate to good. Trend accuracy was very good. The device had no downtimes, but 4 out of 16 external sensors and 2 out of 12 CVCs had practical problems.
authors.affiliation: Department of Intensive Care, Academic Medical Center, Room C3-311, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands. j.h.leopold@amc.uva.nl.|Department of Medical Informatics, Academic Medical Center, Amsterdam, The Netherlands. j.h.leopold@amc.uva.nl.
authors.forename: J H
authors.identifier: http://orcid.org/0000-0002-1495-1216
authors.initials: JH
authors.lastname: Leopold
authors.affiliation: Department of Intensive Care, Academic Medical Center, Room C3-311, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands.
authors.forename: R T M
authors.initials: RTM
authors.lastname: van Hooijdonk
authors.affiliation: Department of Intensive Care, Academic Medical Center, Room C3-311, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Boshuizen
authors.affiliation: Department of Intensive Care, Academic Medical Center, Room C3-311, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands.
authors.forename: T
authors.initials: T
authors.lastname: Winters
authors.affiliation: Department of Intensive Care, Academic Medical Center, Room C3-311, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands.
authors.forename: L D
authors.initials: LD
authors.lastname: Bos
authors.affiliation: Department of Medical Informatics, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: A
authors.initials: A
authors.lastname: Abu-Hanna
authors.affiliation: Department of Clinical Chemistry, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: A M T
authors.initials: AMT
authors.lastname: Hoek
authors.affiliation: Department of Clinical Chemistry, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: J C
authors.initials: JC
authors.lastname: Fischer
authors.affiliation: Department of Clinical Chemistry, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: E C
authors.initials: EC
authors.lastname: van Dongen-Lases
authors.affiliation: Department of Intensive Care, Academic Medical Center, Room C3-311, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands.|Laboratory of Experimental Intensive care and Anesthesiology (L.E.I.C.A), Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: M J
authors.initials: MJ
authors.lastname: Schultz