title: Assessing the performance of handheld glucose testing for critical care.
abstract: BACKGROUND
  We assessed the performance of a point-of-care (POC) glucose meter system (GMS) with multitasking test strip by using the locally-smoothed (LS) median absolute difference (MAD) curve method in conjunction with a modified Bland-Altman difference plot and superimposed International Organization for Standardization (ISO) 15197 tolerance bands. We analyzed performance for tight glycemic control (TGC).
  
  
  METHODS
  A modified glucose oxidase enzyme with a multilayer-gold, multielectrode, four-well test strip (StatStriptrade mark, NOVA Biomedical, Waltham, MA) was used. There was no test strip calibration code. Pragmatic comparison was done of GMS results versus paired plasma glucose measurements from chemistry analyzers in clinical laboratories. Venous samples (n = 1,703) were analyzed at 35 hospitals that used 20 types of chemistry analyzers. Erroneous results were identified using the Bland-Altman plot and ISO 15197 criteria. Discrepant values were analyzed for the TGC interval of 80-110 mg/dL.
  
  
  RESULTS
  The GMS met ISO 15197 guidelines; 98.6% (410 of 416) of observations were within tolerance for glucose <75 mg/dL, and for > or =75 mg/dL, 100% were within tolerance. Paired differences (handheld minus reference) averaged -2.2 (SD 9.8) mg/dL; the median was -1 (range, -96 to 45) mg/dL. LS MAD curve analysis revealed satisfactory performance below 186 mg/dL; above 186 mg/dL, the recommended error tolerance limit (5 mg/dL) was not met. No discrepant values appeared. All points fell in Clarke Error Grid zone A. Linear regression showed y = 1.018x - 0.716 mg/dL, and r2 = 0.995.
  
  
  CONCLUSIONS
  LS MAD curves draw on human ability to discriminate performance visually. LS MAD curve and ISO 15197 performance were acceptable for TGC. POC and reference glucose calibration should be harmonized and standardized.
authors.affiliation: Point-of-Care Testing Center for Teaching and Research and the University of California Davis-Lawrence Livermore National Laboratory Center for Point-of-Care Technology, University of Califorina, Davis, Davis, California, USA. gjkost@ucdavis.edu
authors.forename: Gerald J
authors.initials: GJ
authors.lastname: Kost
authors.forename: Nam K
authors.initials: NK
authors.lastname: Tran
authors.forename: Richard F
authors.initials: RF
authors.lastname: Louie
authors.forename: Nicole L
authors.initials: NL
authors.lastname: Gentile
authors.forename: Victor J
authors.initials: VJ
authors.lastname: Abad
mesh_terms: D001786:Blood Glucose / Q000378:metabolism*; D002138:Calibration; D003422:Critical Care / Q000592:standards*; D006801:Humans; D016018:Least-Squares Analysis; D019095:Point-of-Care Systems / Q000592:standards*; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D001786:Blood Glucose