Table 1.
Mass fraction and current CVs of control materials and percentages of laboratories meeting different quality requirements for HbA1c (%)
| Year | Number of labsa | Mass fraction | Current CVs | Allowable imprecision specifications based on NACB and biological variation | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Median | IQRb | Median | IQRb | P d | NACBc | Minimum | Desirable | Optimal | ||
| Level 1 | ||||||||||
| 2012 | 306 | 5.68 | 0.57 | 2.60 | 2.88 | <.001 | 39.9 | 24.5 | 10.1 | 4.9 |
| 2013 | 306 | 5.67 | 0.49 | 2.09 | 1.77 | 47.0 | 23.1 | 8.0 | 3.6 | |
| 2014 | 306 | 5.35 | 0.64 | 1.90 | 1.58 | 53.5 | 26.2 | 8.5 | 3.2 | |
| 2015 | 306 | 5.34 | 0.58 | 1.90 | 1.56 | 54.3 | 33.2 | 12.5 | 4.3 | |
| 2016 | 306 | 5.45 | 0.63 | 1.61 | 1.52 | 63.4 | 40.7 | 18.1 | 4.9 | |
| Level 2 | ||||||||||
| 2012 | 147 | 9.46 | 0.68 | 2.39 | 2.35 | <.001 | 44.2 | 32.0 | 12.2 | 4.1 |
| 2013 | 158 | 9.60 | 0.97 | 1.83 | 1.49 | 56.3 | 28.1 | 13.3 | 3.1 | |
| 2014 | 173 | 9.58 | 0.78 | 1.78 | 1.46 | 63.7 | 38.9 | 8.3 | 0.6 | |
| 2015 | 171 | 9.69 | 0.73 | 1.53 | 1.13 | 69.9 | 46.8 | 20.5 | 3.2 | |
| 2016 | 177 | 9.83 | 0.67 | 1.49 | 0.94 | 72.3 | 52.5 | 19.1 | 3.5 | |
a
The data in this row reflect the number of laboratories which have submitted the information of current CVs for level 1 and level 2.
b
Interquartile range (IQR) is equal to the difference between the upper and lower quartiles, IQR=Q3‐Q1.
c
Analytical imprecision criteria based on National Academy of Clinical Biochemistry (NACB) was set as <2% within laboratory.
d
Differences in current CVs in different years were tested by Friedman M test.