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Kim, Min, and Park: Evaluation of Fixed Quality Control Range of Bayer Rapidpoint 400 Blood Gas and Electrolyte Analyzer with Six Sigma Metrics
Original Article

Korean J Leg Med 2006;26(6):400-407.

Published online: 10 February 2006

DOI: https://doi.org/10.3343/kjlm.2006.26.6.400

Evaluation of Fixed Quality Control Range of Bayer Rapidpoint 400 Blood Gas and Electrolyte Analyzer with Six Sigma Metrics

Yunhee Kim, M.D.1, Won-Ki Min, M.D.1, Hyosoon Park, M.D.2

1Department of Laboratory Medicine, Asan Medical Center and University of Ulsan College of Medicine, Seoul, Korea

2Department of Laboratory Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea

Received 9 March 2006       Revised 8 October 2006       Accepted 9 October 2006

Copyright © 2006 The Korean Society for Legal Medicine

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Background

Bayer Rapidpoint 400 analyzer for point of care testing (POCT) uses fixed quality control (QC) range even when the lot number of a cartridge for quality control changes. To evaluate the fixed QC range recommended by the manufacturer, we analyzed internal QC data of 9 analyzers with Six Sigma metrics.

Materials and Methods

We investigated QC data of 9 analyzers over 5 months from May to September, 2004 for 8 parameters (pH, pCO2, pO2, Na+, K+, iCa++, Cl-, and glucose). One hundred eighty six groups of QC data were analyzed with capability index (Cp=total allowable error (TEa)/3 standard deviation (SD)) and capability index considering bias (Cpk,=(TEa-bias)/3 SD). Acceptability was evaluated with criteria of 1.33 Cpk, 4 sigma level or quality criteria of the Clinical Laboratory Improvement Amendments of 1988 (CLIA'88).

Results

In 80.7% (150 of 186 groups), both Cp and Cpk were at or above 1.33, which indicated that the use of fixed QC range was adequate. In 19.3% (36 of 186 groups), Cpk was below 1.33, which indicated the inadequacy of fixed QC range. Among them 14.5% (27 of 186 groups) showed Cp below 1.33, indicating that the errors had a random factor and 4.8% (9 of 186 groups) had Cp at or above 1.33, indicating that the errors had a systematic factor.

Conclusions

The quality criteria mandated by CLIA'88 was satisfied in about 80% of study groups using fixed QC ranges, but in about 20%, more strict instrument maintenance and specimen handling by operators, and quality improvement of QC materials by manufacturer was required.

Keywords: Blood gas and electrolyte analyzer, Capability index, Capability index considering bias, Point of care testing, Quality control, Six Sigma

References

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Table 1.
Total coefficient of variation of internal QC results of 8 test items for 5 months
Test item Level of QC materials Target value Total CV of internal quality control results
pH level 1 7.1500 0.05
  level 2 7.3500 0.06
  level 3 7.5500 0.09
pCO2 level 1 70.00 2.74
  level 2 40.00 2.28
  level 3 20.00 3.48
pO2 level 1 150.00 1.31
  level 2 100.00 1.78
  level 3 65.00 2.26
Na level 1 115.00 0.71
  level 2 135.00 0.73
  level 3 155.00 0.85
K level 1 3.00 0.38
  level 2 5.00 0.37
  level 3 7.00 0.44
Cl level 1 80.00 0.79
  level 2 100.00 0.51
  level 3 120.00 0.48
Glucose level 1 200.00 1.32
  level 2 100.00 1.37
  level 3 50.00 2.68
Ca level 1 1.60 1.10
  level 2 1.20 1.05
  level 3 0.80 1.47
Table 2.
Six Sigma metrics of internal QC results of 8 test items for 5 months
pH Target TEa Mean SD Bias Cp Cpk
level 1              
 PICU 7.1500 0.04 7.1426 0.00284 0.0074 4.70 3.83
 NICU 7.1500 0.04 7.1418 0.00427 0.0082 3.12 2.48
 CSICU 7.1500 0.04 7.1491 0.00575 0.0009 2.32 2.27
 MICU 7.1500 0.04 7.1401 0.00414 0.0099 3.22 2.42
 ER 7.1500 0.04 7.1389 0.00286 0.0111 4.66 3.38
 OR 7.1500 0.04 7.1473 0.00380 0.0027 3.51 3.27
 F4 7.1500 0.04 7.1440 0.00290 0.0060 4.60 3.91
 ORF 7.1500 0.04 7.1445 0.00415 0.0055 3.21 2.77
 C4 7.1500 0.04 7.1396 0.00451 0.0104 2.96 2.19
level 2              
 PICU 7.3500 0.04 7.3507 0.00394 0.0007 3.38 3.33
 NICU 7.3500 0.04 7.3504 0.00621 0.0004 2.15 2.12
 CSICU 7.3500 0.04 7.3515 0.00510 0.0015 2.61 2.52
 MICU 7.3500 0.04 7.3487 0.00487 0.0013 2.74 2.65
 ER 7.3500 0.04 7.3466 0.00374 0.0034 3.57 3.26
 OR 7.3500 0.04 7.3540 0.00397 0.0040 3.36 3.02
 F4 7.3500 0.04 7.3524 0.00356 0.0024 3.74 3.52
 ORF 7.3500 0.04 7.3516 0.00281 0.0016 4.75 4.55
 C4 7.3500 0.04 7.3482 0.00599 0.0018 2.23 2.12
level 3              
 PICU 7.5500 0.04 7.5470 0.00639 0.0030 2.09 1.93
 NICU 7.5500 0.04 7.5478 0.00822 0.0022 1.62 1.53
 CSICU 7.5500 0.04 7.5498 0.00686 0.0002 1.94 1.93
 MICU 7.5500 0.04 7.5474 0.00797 0.0026 1.67 1.56
 ER 7.5500 0.04 7.5432 0.00549 0.0068 2.43 2.01
 OR 7.5500 0.04 7.5514 0.00697 0.0014 1.91 1.85
 F4 7.5500 0.04 7.5503 0.00572 0.0003 2.33 2.31
 ORF 7.5500 0.04 7.5492 0.00339 0.0008 3.93 3.85
 C4 7.5500 0.04 7.5460 0.00790 0.0040 1.69 1.52
 pCO2 Target TEa Mean SD Bias Cp Cpk
level 1              
 PICU 70.00 5.00 70.92 1.659 0.92 1.00 0.82
 NICU 70.00 5.00 71.78 2.218 1.78 0.75 0.48
 CSICU 70.00 5.00 72.55 2.334 2.55 0.71 0.35
 MICU 70.00 5.00 73.25 2.482 3.25 0.67 0.23
 ER 70.00 5.00 73.30 2.156 3.30 0.77 0.26
 OR 70.00 5.00 70.42 1.986 0.42 0.84 0.77
 F4 70.00 5.00 71.39 1.361 1.39 1.22 0.88
 ORF 70.00 5.00 70.49 1.088 0.49 1.53 1.38
 C4 70.00 5.00 72.86 2.470 2.86 0.67 0.29
level 2              
 PICU 40.00 5.00 38.31 1.034 1.69 1.61 1.07
 NICU 40.00 5.00 39.51 0.896 0.49 1.86 1.68
 CSICU 40.00 5.00 40.49 1.212 0.49 1.38 1.24
 MICU 40.00 5.00 39.82 0.816 0.18 2.04 1.97
 ER 40.00 5.00 39.34 0.945 0.66 1.76 1.53
 OR 40.00 5.00 38.51 0.776 1.49 2.15 1.51
 F4 40.00 5.00 39.15 0.604 0.85 2.76 2.29
 ORF 40.00 5.00 39.02 0.727 0.98 2.29 1.84
 C4 40.00 5.00 40.08 1.074 0.08 1.55 1.53
level 3              
 PICU 22.00 5.00 21.26 0.749 0.74 2.22 1.89
 NICU 22.00 5.00 22.13 0.749 0.13 2.22 2.17
 CSICU 22.00 5.00 21.66 0.952 0.34 1.75 1.63
 MICU 22.00 5.00 22.31 0.809 0.31 2.06 1.93
 ER 22.00 5.00 21.60 0.805 0.40 2.07 1.91
 OR 22.00 5.00 21.12 0.663 0.88 2.51 2.07
 F4 22.00 5.00 21.89 0.663 0.11 2.51 2.46
 ORF 22.00 5.00 21.75 0.566 0.25 2.94 2.80
 C4 22.00 5.00 22.51 0.877 0.51 1.90 1.71
 pO2 Target TEa Mean SD Bias Cp Cpk
level 1              
 PICU 150.00 15.00 151.30 1.277 1.30 3.91 3.58
 NICU 150.00 15.00 151.10 1.973 1.10 2.53 2.35
 CSICU 150.00 15.00 149.04 1.498 0.96 3.34 3.12
 MICU 150.00 15.00 146.26 2.624 3.74 1.91 1.43
 ER 150.00 15.00 151.51 0.989 1.51 5.06 4.55
 OR 150.00 15.00 151.95 2.510 1.95 1.99 1.73
 F4 150.00 15.00 151.39 1.739 1.39 2.88 2.61
 ORF 150.00 15.00 150.96 2.370 0.96 2.11 1.97
 C4 150.00 15.00 150.96 2.712 0.96 1.84 1.73
level 2              
 PICU 100.00 10.00 97.42 1.314 2.58 2.54 1.88
 NICU 100.00 10.00 99.80 2.736 0.20 1.22 1.19
 CSICU 100.00 10.00 100.39 1.288 0.39 2.59 2.49
 MICU 100.00 10.00 100.20 1.286 0.20 2.59 2.54
 ER 100.00 10.00 98.19 0.835 1.81 3.99 3.27
 OR 100.00 10.00 101.42 2.504 1.42 1.33 1.14
 F4 100.00 10.00 97.91 1.391 2.09 2.40 1.90
 ORF 100.00 10.00 99.78 2.113 0.22 1.58 1.54
 C4 100.00 10.00 99.78 2.535 0.22 1.31 1.29
level 3              
 PICU 65.00 6.50 62.92 1.276 2.08 1.70 1.15
 NICU 65.00 6.50 63.91 1.465 1.09 1.48 1.23
 CSICU 65.00 6.50 61.42 1.251 3.58 1.73 0.78
 MICU 65.00 6.50 63.92 1.926 1.08 1.13 0.94
 ER 65.00 6.50 63.62 0.799 1.38 2.71 2.13
 OR 65.00 6.50 63.95 1.732 1.05 1.25 1.05
 F4 65.00 6.50 63.38 1.222 1.62 1.77 1.33
 ORF 65.00 6.50 63.50 1.859 1.50 1.17 0.90
 C4 65.00 6.50 64.45 1.391 0.55 1.56 1.43
 Na+ Target TEa Mean SD Bias Cp Cpk
level 1              
 PICU 115.00 4.00 114.92 1.209 0.08 1.10 1.08
 NICU 115.00 4.00 114.82 0.714 0.18 1.87 1.79
 CSICU 115.00 4.00 114.82 0.824 0.18 1.62 1.55
 MICU 115.00 NT NT NT NT NT NT
 ER 115.00 4.00 115.15 0.741 0.15 1.80 1.73
 OR 115.00 4.00 114.85 0.873 0.15 1.53 1.47
 F4 115.00 4.00 114.99 0.537 0.01 2.48 2.48
 ORF 115.00 4.00 114.60 0.750 0.40 1.78 1.60
 C4 115.00 4.00 115.30 0.847 0.30 1.57 1.46
level 2              
 PICU 135.00 4.00 133.80 1.550 1.20 0.86 0.60
 NICU 135.00 4.00 134.54 0.837 0.46 1.59 1.41
 CSICU 135.00 4.00 135.47 0.955 0.47 1.40 1.23
 MICU 135.00 NT NT NT NT NT NT
 ER 135.00 4.00 134.77 1.069 0.23 1.25 1.18
 OR 135.00 4.00 134.17 1.213 0.83 1.10 0.87
 F4 135.00 4.00 134.38 0.658 0.62 2.03 1.71
 ORF 135.00 4.00 134.22 0.760 0.78 1.75 1.41
 C4 135.00 4.00 135.04 0.827 0.04 1.61 1.60
level 3              
 PICU 155.00 4.00 152.86 2.017 2.14 0.66 0.31
 NICU 155.00 4.00 154.19 1.200 0.81 1.11 0.89
 CSICU 155.00 4.00 155.68 1.490 0.68 0.90 0.74
 MICU 155.00 NT NT NT NT NT NT
 ER 155.00 4.00 154.48 1.177 0.52 1.13 0.99
 OR 155.00 4.00 153.37 1.587 1.63 0.84 0.50
 F4 155.00 4.00 153.78 0.875 1.22 1.52 1.06
 ORF 155.00 4.00 153.88 0.981 1.12 1.36 0.98
 C4 155.00 4.00 154.78 1.190 0.22 1.12 1.06
K+ Target TEa Mean SD Bias Cp Cpk
level 1              
 PICU 3.00 0.50 3.01 0.013 0.01 12.81 12.54
 NICU 3.00 0.50 3.01 0.009 0.01 18.84 18.63
 CSICU 3.00 0.50 3.01 0.012 0.01 14.42 14.27
 MICU 3.00 NT NT NT NT NT NT
 ER 3.00 0.50 3.00 0.014 0.00 12.28 12.17
 OR 3.00 0.50 3.01 0.013 0.01 13.01 12.69
 F4 3.00 0.50 3.01 0.010 0.01 16.55 16.18
 ORF 3.00 0.50 3.00 0.009 0.00 17.67 17.55
 C4 3.00 0.50 3.01 0.012 0.01 14.21 13.99
level 2              
 PICU 5.00 0.50 4.97 0.023 0.03 7.21 6.82
 NICU 5.00 0.50 4.99 0.016 0.01 10.69 10.38
 CSICU 5.00 0.50 5.01 0.024 0.01 6.92 6.79
 MICU 5.00 NT NT NT NT NT NT
 ER 5.00 0.50 4.98 0.016 0.02 10.67 10.31
 OR 5.00 0.50 4.98 0.021 0.02 7.92 7.66
 F4 5.00 0.50 4.98 0.015 0.02 11.05 10.61
 ORF 5.00 0.50 4.98 0.017 0.02 9.92 9.45
 C4 5.00 0.50 4.99 0.017 0.01 10.07 9.82
level 3              
 PICU 7.00 0.50 6.97 0.037 0.03 4.45 4.18
 NICU 7.00 0.50 7.01 0.027 0.01 6.12 6.04
 CSICU 7.00 0.50 7.03 0.031 0.03 5.46 5.10
 MICU 7.00 NT NT NT NT NT NT
 ER 7.00 0.50 7.00 0.023 0.00 7.09 7.03
 OR 7.00 0.50 6.99 0.043 0.01 3.90 3.80
 F4 7.00 0.50 6.98 0.025 0.02 6.56 6.30
 ORF 7.00 0.50 6.99 0.032 0.01 5.22 5.06
 C4 7.00 0.50 7.00 0.028 0.00 5.85 5.81
iCa++ Target TEa Mean SD Bias Cp Cpk
level 1              
 PICU 1.60 0.25 1.63 0.015 0.03 5.60 5.01
 NICU 1.60 0.25 1.64 0.026 0.04 3.16 2.65
 CSICU 1.60 0.25 1.63 0.019 0.03 4.38 3.88
 MICU 1.60 NT NT NT NT NT NT
 ER 1.60 0.25 1.62 0.025 0.02 3.32 3.03
 iCa++ Target TEa Mean SD Bias Cp Cpk
 OR 1.60 0.25 1.62 0.015 0.02 5.64 5.13
 F4 1.60 0.25 1.62 0.011 0.02 7.70 7.13
 ORF 1.60 0.25 1.62 0.013 0.02 6.20 5.64
 C4 1.60 0.25 1.62 0.019 0.02 4.50 4.15
level 2              
 PICU 1.20 0.25 1.22 0.010 0.02 8.50 7.98
 NICU 1.20 0.25 1.23 0.019 0.03 4.47 4.00
 CSICU 1.20 0.25 1.21 0.015 0.01 5.39 5.12
 MICU 1.20 NT NT NT NT NT NT
 ER 1.20 0.25 1.21 0.019 0.01 4.46 4.20
 OR 1.20 0.25 1.22 0.010 0.02 8.48 7.66
 F4 1.20 0.25 1.22 0.008 0.02 10.07 9.45
 ORF 1.20 0.25 1.22 0.009 0.02 9.30 8.50
 C4 1.20 0.25 1.21 0.013 0.01 6.60 6.21
level 3              
 PICU 0.80 0.25 0.81 0.010 0.01 8.64 8.37
 NICU 0.80 0.25 0.80 0.013 0.00 6.21 6.17
 CSICU 0.80 0.25 0.80 0.012 0.00 7.07 6.97
 MICU 0.80 NT NT NT NT NT NT
 ER 0.80 0.25 0.81 0.017 0.01 4.86 4.66
 OR 0.80 0.25 0.81 0.015 0.01 5.38 5.08
 F4 0.80 0.25 0.81 0.007 0.01 11.32 10.76
 ORF 0.80 0.25 0.81 0.008 0.01 10.00 9.62
 C4 0.80 0.25 0.81 0.012 0.01 7.21 6.81
CI- Target TEa Mean SD Bias Cp Cpk
level 1              
 PICU 80.00 4.00 81.18 0.388 1.18 3.44 2.42
 NICU 80.00 NT NT NT NT NT NT
 CSICU 80.00 4.00 79.06 0.286 0.94 4.65 3.56
 MICU 80.00 NT NT NT NT NT NT
 ER 80.00 4.00 81.19 0.393 1.19 3.39 2.38
 OR 80.00 4.00 80.90 1.396 0.90 0.95 0.74
 F4 80.00 4.00 81.03 0.396 1.03 3.36 2.50
 ORF 80.00 4.00 80.71 0.876 0.71 1.52 1.25
 C4 80.00 4.00 81.49 0.717 1.49 1.86 1.17
level 2              
 PICU 100.00 5.00 100.52 0.501 0.52 3.32 2.98
 NICU 100.00 NT NT NT NT NT NT
 CSICU 100.00 5.00 99.74 0.887 0.26 1.88 1.78
 MICU 100.00 NT NT NT NT NT NT
 ER 100.00 5.00 100.20 0.450 0.20 3.71 3.56
 OR 100.00 5.00 100.17 0.377 0.17 4.42 4.27
 F4 100.00 5.00 100.16 0.371 0.16 4.49 4.35
 ORF 100.00 5.00 100.30 0.460 0.30 3.62 3.40
 C4 100.00 5.00 100.46 0.513 0.46 3.25 2.95
level 3              
 PICU 120.00 6.00 119.94 0.700 0.06 2.86 2.83
 NICU 120.00 NT NT NT NT NT NT
 CSICU 120.00 6.00 120.09 0.578 0.09 3.46 3.41
 MICU 120.00 NT NT NT NT NT NT
 ER 120.00 6.00 119.76 0.629 0.24 3.18 3.05
 OR 120.00 6.00 119.35 0.519 0.65 3.85 3.44
 F4 120.00 6.00 119.60 0.589 0.40 3.40 3.17
 ORF 120.00 6.00 119.51 0.575 0.49 3.48 3.19
 C4 120.00 6.00 120.03 0.472 0.03 4.24 4.22
Glucose Target TEa Mean SD Bias Cp Cpk
level 1              
 PICU 200.00 20.00 197.3 2.03 2.7 3.28 2.84
 NICU 200.00 NT NT NT NT NT NT
 CSICU 200.00 NT NT NT NT NT NT
 MICU 200.00 NT NT NT NT NT NT
 ER 200.00 NT NT NT NT NT NT
 OR 200.00 NT NT NT NT NT NT
 F4 200.00 20.00 198.1 1.95 1.9 3.43 3.10
 ORF 200.00 20.00 199.4 3.68 0.6 1.81 1.76
 C4 200.00 20.00 196.1 2.68 3.9 2.48 2.00
level 2              
 PICU 100.00 10.00 100.5 1.44 0.5 2.32 2.21
 NICU 100.00 NT NT NT NT NT NT
 CSICU 100.00 NT NT NT NT NT NT
 MICU 100.00 NT NT NT NT NT NT
 ER 100.00 NT NT NT NT NT NT
 OR 100.00 NT NT NT NT NT NT
 F4 100.00 10.00 101.2 1.11 1.2 3.01 2.64
 ORF 100.00 10.00 100.7 1.73 0.7 1.92 1.79
 C4 100.00 10.00 98.9 1.21 1.1 2.76 2.45
level 3              
 PICU 50.00 5.00 49.9 0.97 0.1 1.72 1.68
 NICU 50.00 NT NT NT NT NT NT
 CSICU 50.00 NT NT NT NT NT NT
 MICU 50.00 NT NT NT NT NT NT
 ER 50.00 NT NT NT NT NT NT
 OR 50.00 NT NT NT NT NT NT
 F4 50.00 5.00 50.4 0.89 0.4 1.87 1.73
 ORF 50.00 5.00 50.6 1.56 0.6 1.07 0.95
 C4 50.00 5.00 48.8 2.21 1.2 0.75 0.57

Abbreviations: TEa, total allowable error; SD, standard deviation; bias, assigned value minus mean; Cp, capability index, total allowable error (TEa)/3 SD; Cpk, capability index considering bias, (TEa – bias)/3 SD; PICU, pediatric intensive care unit; NICU, neonatal intensive care unit; CSICU, cardiac surgery intensive care unit; MICU, internal medicine intensive care unit; ER, emergency room; OR, F4, ORF and C4, a kind of name for operating rooms; NT, not tested.

Table 3.
Acceptability of fixed QC range
Cp ≥ 1.33 and Cpk ≥ 1.33 80.7% (150 of 186 groups) Acceptable by the quality criteria of all the other groups except CLIA'88 unacceptable groups
Cp ≥ 1.33 and Cpk <1.33 4.8% (9 of 186 groups) Unacceptable by systematic error
    pCO2-level 2-PICU, pCO2-level 2-CSICU
    pO2-level 3-NICU, pO2-level 3-PICU, pO2-level 3-CSICU
    Cl-level 1-ORF, Cl-level 1-C4, Na-level 2-CSICU, Na-level 3-F4
Cp < 1.33 14.5% (27 of 186 groups) Unacceptable by random error with or without systematic error
    Glucose-level 3-C4, ORF
    pCO2-level 1-MICU, CSICU, C4, NICU, ER, OR, PICU, F4
    pCO2-level 2-NICU, C4, OR
    pCO2-level 3-MICU, ORF, OR
    Cl-level 1-OR
    Na-level 1-PICU
    Na-level 2-PICU, OR, ER
    Na-level 3-CSICU, OR, PICU, NICU, C4, ER
Table 4.
Comparison of Cp level of fixed control limits between manufacturer's SD and averages of SD of internal QC results of 9 networked POCT gas analyzers over 5 months
Test item QC materials Target value SD established by manufactures SD of QC results of this hospitals Fixed control limits Cp* by SD of manufactures Cp† by SD of QC results of this hospital Difference of Cp between SD of manufactures and SD of QC results of this hospital
pH level 1 7.1500 0.005 0.00390 0.02 1.3 1.7 0.4
  level 2 7.3500 0.005 0.00450 0.02 1.3 1.5 0.1
  level 3 7.5500 0.005 0.00650 0.02 1.3 1.0 −0.3
pCO2 level 1 70.00 0.83 1.973 6.4 2.6 1.1 −1.5
  level 2 40.00 1.09 0.898 5 1.5 1.9 0.3
  level 3 20.00 0.52 0.759 3 1.9 1.3 −0.6
pO2 level 1 150.00 1.62 1.966 11 2.3 2.0 −0.4
  level 2 100.00 0.81 1.778 7.8 3.2 1.5 −1.7
  level 3 65.00 1.61 1.436 9.2 1.9 2.1 0.2
Na level 1 115.00 0.64 0.812 5 2.6 2.1 −0.6
  level 2 135.00 0.96 0.984 5 1.7 1.7 0.0
  level 3 155.00 0.85 1.315 7 2.7 1.8 −1.0
K level 1 3.00 0.01 0.011 0.3 10.0 8.8 −1.3
  level 2 5.00 0.03 0.019 0.3 3.3 5.4 2.1
  level 3 7.00 0.04 0.031 0.3 2.5 3.2 0.7
Cl level 1 80.00 0.74 0.636 6 2.7 3.1 0.4
  level 2 100.00 0.83 0.508 6 2.4 3.9 1.5
  level 3 120.00 0.76 0.580 6 2.6 3.4 0.8
Glucose level 1 200.00 1.65 2.585 14 2.8 1.8 −1.0
  level 2 100.00 1.24 1.373 10 2.7 2.4 −0.3
  level 3 50.00 1.07 1.408 10 3.1 2.4 −0.7
Ca level 1 1.60 0.01 0.018 0.1 4.0 2.2 −1.8
  level 2 1.20 0.01 0.013 0.1 3.3 2.6 −0.7
  level 3 0.80 0.01 0.012 0.1 3.3 2.8 −0.5

* fixed control limits / 3 SD established by manufactures;

† fixed control limits/3 SD of QC results of this hospitals. Abbreviations: See Table 2.

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