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Test ID: HbA1c
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HbA1c
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Useful For
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To help diagnose and monitor diabetic and prediabetic patients.
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Method name and description
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Turbidimetric Inhibition Immunoassay (TINIA)
Turbidimetric inhibition immunoassay (TINIA) for hemolyzed whole blood performed on the Roche cobas c-systems. This method uses Tetradecyltrimethylammonium bromide as the detergent in the hemolyzing reagent to eliminate interference from leukocytes (TTAB does not lyse leukocytes). Sample pretreatment to remove labile HbA1c is not necessary. Patient sample reacts with anti-HbA1c antibody to form soluble antigen-antibody complexes. Since the specific HbA1c antibody site is present only once on the HbA1c molecule, formation of insoluble complexes does not take place. After buffer/polyhaptens is added, it react with excess anti-HbA1c antibodies to form an insoluble antibody-polyhapten complex which can be determined turbidimetrically.
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Clinical information
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HbA1c is one of the glycated hemoglobins, a subfraction formed by the attachment of various sugars to the Hb molecule. HbA1c is formed in two steps by the non-enzymatic reaction of glucose with the N‑terminal amino group of the β‑chain of normal adult Hb (HbA). In the erythrocytes, the relative amount of HbA converted to stable HbA1c increases with the average concentration of glucose in the blood thus HbA1c reflects the average blood glucose level during the preceding 2 to 3 months and is suitable to monitor long-term blood glucose control in individuals with diabetes mellitus. In certain clinical situations, such as gestational diabetes, or after a major change in therapy, it may be useful to measure HbA1c in 2 to 4 week intervals. (Roche Cobas Tina-quant Hemoglobin A1cDx Gen.3 package insert ; Roche Diagnostic Corp., Indianapolis, IN)
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Specimen type / Specimen volume / Specimen container
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Specimen type: Whole blood
Minimum volume of sample: 4 mL
Whole blood: K2-EDTA, K3-EDTA,
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Collection instructions / Special Precautions / Timing of collection
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Anticoagulated specimens should be properly mixed upon extraction to avoid clot and microclot formations.
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Storage and transport instructions
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Storage: 3 days at 15 – 25°C
7 days at 2 – 8°C;
6 months at ‑20 °C (± 5 °C)
Transport: 2-25°C
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Specimen Rejection Criteria
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Wrong collection container and clotted sample.
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Biological reference intervals and clinical decision values
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Interpretative Data:
Desirable: < 5.7%
Pre-Diabetes: 5.7 -6.4%
Diabetes: 6.5% or higher
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Turnaround time / Days and times test performed / Specimen retention time
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Daily (24/7)
Turn-around time:
Routine: One working day
Specimen Retention: 4 days
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