Methods, units and quality requirements for the analysis of haemoglobin A1c in diabetes mellitus

Table 1 The methods commonly used for analyzing hemoglobin A_1c according to the surveys conducted by Labquality Ltd. in 1994

Numerical summary from a diabetic EDTA-blood sample 1/1994
Analyte/method group	Mean	SD	CV%	Number
GHbA1c %
Ion exchange Ciba Corning	8.7	0.4	4.3	4
Ion exchange Diamat Biorad	9.7	0.8	8.4	15
Ion exchange Kyoto Daichii	8.4	0.3	3.4	3
Ion exchange Pharmacia MonoS	9.0	0.8	8.7	17
Ion exchange Shimadzu	10.7	0.1	0.7	2
Ion exchange others	9.5	0.8	7.9	5
Ion exchange minicolumn Biorad	9.7	0.8	8.1	4
Electrophoresis Beckman	9.7	0.8	7.8	8
Affininity method Abbott Imx	8.4	0.6	7.5	15
Affininity method Abbott Vision	8.8	0.4	4.8	8
LaInIA Ames DCA 2000	9.1	0.2	2.6	29
TinIA Boehringer	9.1	1.0	10.4	15
Immunochemical others	8.8	1.7	19.3	2
All method groups	9.2	0.8	8.9	127
GHbA1
Ion exchange Ciba Corning	11.8	0.3	2.4	2
Ion exchange Diamat Bio-Rad	12.1	0.4	3.2	7
Ion exchange others	11.5	-	-	1
All methods groups	12.0	0.4	3.3	10
GHb
Affinity method Abbott Imx	13.4	0.4	2.7	2
Affinity method mini col Isolab	10.3	1.4	13.7	2
All method groups	11.8	2.0	16.5	4

HbA_1c: Hemoglobin A_1c.

Table 2 The methods commonly used for analyzing hemoglobin A_1c according to the surveys conducted by Labquality Ltd. in 2015

Numerical summary from a diabetic EDTA-blood sample 5/2015
Analyte/method group	Mean	SD	CV%	Min	Max	Number
HbA1c, mmol/mol
Abbott Arhitect enzymatic	53.64	2.45	4.6	48.4	32.1	6
Axis-Shield Afinion	54.70	2.17	4.0	51.0	58.0	44
Beckman Coulter	55.2					1
Hemoque	51.4	3.98	7.7	46.0	55.0	5
HPLC Bio-Rad D-10	55.00					1
HPLC Bio-Rad Variant	56.00	3.21	5.7	54.0	58.0	2
HPLC Tosoh	56.42	1.23	2.2	35.6	59.8	33
Roche Cobas c Tina-Quant	54.76	2.56	4.7	33.0	57.0	13
Roche Cobas Integra	55.0					1
Rocgw Tina Quant	56.00					1
Siemens Advia Centaur	57.93					1
Siemens DCA 2000+ and Vant	55.05	1.96	3.6	51.0	58.0	33
Thermo Scientific Konelab	54.44	2.63	4.8	48.0	58.4	24
All	55.05	2.17	3.9	32.1	59.8	165
HbA1c
Abbott Arhitect enzymatic	7.20	0.00	0.0	7.2	7.2	3
Axis-Shield Afinion	7.17	0.21	2.9	6.9	7.5	44
Beckman Coulter	7.2					1
Hemoqe	6.88	0.25	3.7	6.6	7.2	6
HPLC Bio-Rad D-10	7.2					1
HPLC Bio-Rad Variant	7.5					1
HPLC Tosoh	7.34	0.13	1.8	7.0	8.8	23
Roche Cobas c Tina-Quant	7.29	0.12	1.6	6.7	7.4	7
Siemens Advia Centaur	7.45			5.8	7.0	1
Siemens DCA 2000+ and Vant	7.19	0.18	2.6	6.8	7.5	31
Thermo Scientific Konelab	7.13	0.25	3.5	6.6	7.5	26
All	7.20	0.21	2.9	6.6	8.8	143

HbA_1c: Hemoglobin A_1c.

Table 3 Summary of the questionnaires about the use of the hemoglobin A_1c units sent to 35-51 societies of laboratory medicine (mainly clinical chemistry) and returned by 28.12.2014

Year	2009	2011	2013	2014
Queries sent	35	37	47	51
Only % unit	16	14	15	17
Parallel units, % and mmol/mol	4	9	12	11
mmol/mol unit only in use	(1)	6	11	13
No reply	15	8	9	10

¹Germany was the first country which adopted the exclusive use of mmol/mol unit for HbA1c from 1.1.2010. The questionnaires have been dispatched by e-mail, telefax and mail mainly to Europe and to a small extent outside of Europe from 2009 to 2014.

Table 4 The relationships between the hemoglobin A_1c units as % values to the mmol/mol values are presented at different levels of hemoglobin A_1c

HbA1c	HbA1c	HbA1c
	(%)	(mmol/mol)
Reference limits	4.0-6.0	20-42
Diagnosis limit	6.5	48
Treatment limits, adults	7.0	53
children < 6 yr	7.5	69
children 6-12 yr	8.0	64
children 13-19 yr	8.5	58
Poor diabetic balance	9.0	75
Very poor diabetic balance	12.0	108

Equarions from the NGSP/DCCT mean values to the IFCC units: % = 0.095 × mmol/mol + 2.15; mmol/mol = 10.93 × % - 23.5. The table also shows the most important equations to convert the results described in % units of NGSP/DCCT into the values of IFCC expressed as mmol/mol units[23]. HbA_1c: Hemoglobin A_1c; NGSP/DCCT: National Glycohemoglobin Standardization Program/the Diabetes Control and Complicatioins Trial Research Group; IFCC: International Federation of Clinical Chemistry.