Table 5.

Proportion of laboratories by control rules or control frequency and percentages of acceptable laboratories against different allowable imprecision specifications for HbA1c (%)a

IQC practice	Proportion of laboratories					Allowable imprecision specifications based on NACB and biological variationb
	2012	2013	2014	2015	2016	NACBc	Minimum	Desirable	Optimal
IQC rules
Single IQC rule	18.3	18.5	10.9	7.9	7.6	30.8	21.7	5.6	0
12s/13s	4.0	3.3	2.5	8.2	9.3	50.8	40.2	19.5	5.1
13s/22s	10.8	14.4	14.2	20.0	19.0	60.1	39.8	18.6	0
12s/13s/22s	2.2	3.3	5.5	8.6	10.1	63.2	43.2	16.5	6.9
13s/22s/R4s	5.0	4.5	8.0	12.1	15.6	65.2	42.1	17.9	5.4
One or more from the rules of 12s, 13s, 22s, R4s, 41s and ${10}_{\overline{X}}$	15.1	18.1	16.7	37.5	32.9	59.5	39.9	13.2	6.5
Other rules	2.2	0.8	0.4	2.5	4.2	48.9	30.2	8.9	5.3
Unclear	42.4	37.0	41.8	3.2	1.3	35.6	20.5	6.8	0
IQC frequency
One QC run every more than 2 days	27.5	14.7	12.4	14.7	7.9	33.2	25.6	0	0
One QC run every 1‐2 days	71.9	84.5	85.9	82.4	57.7	61.2	39.4	18.9	5.2
More than one QC run per day	0.6	0.8	1.8	2.8	34.4	67.8	40.3	20.1	7.9

^aThe subgroup analyses of the current CVs, mass fraction and pass rates were all for level 1.

^bThe pass rates against four criteria were for the 2016 data.

^cAnalytical imprecision criteria based on National Academy of Clinical Biochemistry (NACB) was set as <2% within laboratory.