Cas Weykamp1, Garry John2, Philippe Gillery3, Emma English4, Linong Ji5, Erna Lenters-Westra6, Randie R Little7, Gojka Roglic8, David B Sacks9, Izumi Takei10. 1. Department of Clinical Chemistry and European Reference Laboratory, Location Queen Beatrix Hospital, Winterswijk, the Netherlands; c.w.weykamp@skbwinterswijk.nl. 2. Norfolk and Norwich University Hospital, Norwich, UK; 3. Laboratory of Pediatric Biology and Research, University Hospital of Reims, Reims, France; 4. School of Medicine, University of Nottingham, Royal Derby Hospital Site, Derby, UK; 5. Peking University People's Hospital, Beijing, China; 6. Department of Clinical Chemistry, Isala Clinics, Zwolle, the Netherlands; European Reference Laboratory, Location Isala, Zwolle, the Netherlands; 7. Departments of Pathology and Child Health, University of Missouri School of Medicine, Columbia, MO; 8. Department of Management of Noncommunicable Diseases, World Health Organization, Geneva, Switzerland; 9. Department of Laboratory Medicine, NIH, Bethesda, MD; 10. Diabetes and Endocrine Department, Ichikawa General Hospital, Ichikawa, Japan.
Abstract
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.
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.
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