title: Point-of-care testing of HbA1C is traceable to IFCC reference method by external calibration.
abstract: BACKGROUND
  POCT for HbA1C is widely used in China. However, the lack of traceability of POCT leads to poor comparability of patient results.
  
  
  METHODS
  The first step was the evaluation of the precision of NycoCard and DCA by using two-level patient specimens. The second step was the calibration of the central laboratory instrument G8 HBA1C Variant with samples whose values had been assigned by an IFCC reference method. The third step was the assignment of values to 50 fresh whole blood patient specimens by this calibrated G8. The fourth step was to use these 50 fresh whole blood patient specimens to calibrate and to revise the POCT instruments. The fifth step was to confirm whether these 50 specimens were required through mathematical calculations.
  
  
  RESULTS
  The low and high CVs at levels were 3.61% and 1.85% for NycoCard but 1.71% and 2.85% for DCA. The linear equation of NycoCard to calibrated G8 and that of DCA to calibrated G8 were Y=0.8530X+0.6409 and Y=0.8995X+0.3891, respectively, and the correlation coefficient for every POCT instrument was greater than 0.985. By external calibration of POCT instruments, the mean deviation detected by NycoCard was reduced from -4.0±3.4mmol/mol to 0.5±3.9mmol/mol, and that by DCA went down to 0.2±3.3mmol/mol. The minimum specimen size for the external calibration of POCT instrument was 10.
  
  
  CONCLUSIONS
  POCT measurement traceability can be established by external calibration. Using an external calibration mode improves the comparability of POCT patient results.
authors.affiliation: Clinical Laboratory of Beijing Chao-yang Hospital Affiliated to Capital Medical University, Beijing, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Zhou
authors.affiliation: Beijing Center for Clinical Laboratories, Beijing, China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Tong
authors.affiliation: Clinical Laboratory of Beijing Chao-yang Hospital Affiliated to Capital Medical University, Beijing, China.
authors.forename: Chang
authors.initials: C
authors.lastname: Zuo
authors.affiliation: Clinical Laboratory of Fang-Shan-Liang-Xiang Hospital, Beijing, China.
authors.forename: Zhi-Xin
authors.initials: ZX
authors.lastname: Song
authors.affiliation: Eye Hospital, China Academy of Chinese Medical Sciences, Beijing, China.
authors.forename: Huai-An
authors.initials: HA
authors.lastname: Ma
authors.affiliation: Beijing Center for Clinical Laboratories, Beijing, China.
authors.forename: Yu-Hong
authors.initials: YH
authors.lastname: Yue
authors.affiliation: Clinical Laboratory of Beijing Chao-yang Hospital Affiliated to Capital Medical University, Beijing, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Zhang
authors.affiliation: Clinical Laboratory of Beijing Chao-yang Hospital Affiliated to Capital Medical University, Beijing, China; Beijing Center for Clinical Laboratories, Beijing, China. Electronic address: wqt36@163.com.
authors.forename: Qing-Tao
authors.initials: QT
authors.lastname: Wang
mesh_terms: D001774:Blood Chemical Analysis / Q000592:standards*; D002138:Calibration; D006442:Glycated Hemoglobin / Q000032:analysis*; D006801:Humans; D019095:Point-of-Care Systems / Q000592:standards*; D012015:Reference Standards
chemical_list: D006442:Glycated Hemoglobin
keywords: HbA(1C); Measurement traceability; Point-of-care testing