Investigation of 2 models to set and evaluate quality targets for hb a1c: biological variation and sigma-metrics.
BACKGROUND
A major objective of the IFCC Task Force on Implementation of HbA1c Standardization is to develop a model to define quality targets for glycated hemoglobin (Hb A1c).


METHODS
Two generic models, biological variation and sigma-metrics, are investigated. We selected variables in the models for Hb A1c and used data of external quality assurance/proficiency testing programs to evaluate the suitability of the models to set and evaluate quality targets within and between laboratories.


RESULTS
In the biological variation model, 48% of individual laboratories and none of the 26 instrument groups met the minimum performance criterion. In the sigma-metrics model, with a total allowable error (TAE) set at 5 mmol/mol (0.46% NGSP), 77% of the individual laboratories and 12 of 26 instrument groups met the 2σ criterion.


CONCLUSIONS
The biological variation and sigma-metrics models were demonstrated to be suitable for setting and evaluating quality targets within and between laboratories. The sigma-metrics model is more flexible, as both the TAE and the risk of failure can be adjusted to the situation-for example, requirements related to diagnosis/monitoring or international authorities. With the aim of reaching (inter)national consensus on advice regarding quality targets for Hb A1c, the Task Force suggests the sigma-metrics model as the model of choice, with default values of 5 mmol/mol (0.46%) for TAE and risk levels of 2σ and 4σ for routine laboratories and laboratories performing clinical trials, respectively. These goals should serve as a starting point for discussion with international stakeholders in the field of diabetes.
Department of Clinical Chemistry and European Reference Laboratory, Location Queen Beatrix Hospital, Winterswijk, the Netherlands; c.w.weykamp@skbwinterswijk.nl.
Cas
C
Weykamp
Norfolk and Norwich University Hospital, Norwich, UK;
Garry
G
John
Laboratory of Pediatric Biology and Research, University Hospital of Reims, Reims, France;
Philippe
P
Gillery
School of Medicine, University of Nottingham, Royal Derby Hospital Site, Derby, UK;
Emma
E
English
Peking University People's Hospital, Beijing, China;
Linong
L
Ji
Department of Clinical Chemistry, Isala Clinics, Zwolle, the Netherlands; European Reference Laboratory, Location Isala, Zwolle, the Netherlands;
Erna
E
Lenters-Westra
Departments of Pathology and Child Health, University of Missouri School of Medicine, Columbia, MO;
Randie R
RR
Little
Department of Management of Noncommunicable Diseases, World Health Organization, Geneva, Switzerland;
Gojka
G
Roglic
Department of Laboratory Medicine, NIH, Bethesda, MD;
David B
DB
Sacks
Diabetes and Endocrine Department, Ichikawa General Hospital, Ichikawa, Japan.
Izumi
I
Takei
D006442:Glycated Hemoglobin / Q000378:metabolism* / Q000592:standards; D006801:Humans; D007753:Laboratories; D008954:Models, Biological
D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human