En diabetes, la HbA1C esta afectada si el paciente presenta hemoglobina baja?

In diabetes, is the HBA1C affected if the patient has a low haemoglobin? If so, does for example, any anaemia need to be corrected & how long after before re-checking HBA1C? What conditions may affect HBA1C?

Answer:

19 May 2008 note: This question is over 2 years old and may differ to any new research.

The US National Glycohemoglobin Standization Programme (NGSP) web site contains a section on factors that interfere with HbA1c test results on which it states:

“Shortened Erythrocyte Survival: Any condition that shortens erythrocyte survival or decreases mean erythrocyte age (e.g., recovery from acute blood loss, hemolytic anemia) will falsely lower HbA1c test results regardless of the assay method used (23).  HbA1c results from patients with HbSS, HbCC, and HbSC must be interpreted with caution given the pathological processes, including anemia, increased red cell turnover, transfusion requirements, that adversely impact HbA1c as a marker of long-term glycemic control.  Alternative forms of testing such as glycated serum protein (fructosamine) should be considered for these patients.

Other factors: Vitamins C and E are reported to falsely lower test results, possibly by inhibiting glycation of hemoglobin (24, 25); vitamin C may increase values with some assays (25).  Iron-deficiency anemia is reported to increase test results (26).  Hypertriglyceridemia, hyperbilirubinemia, uremia (see carbamylated Hb in Table 1), chronic alcoholism, chronic ingestion of salicylates, and opiate addiction are reported to interfere with some assay methods, falsely increasing results (3, 5, 9, 11, 12, 14, 16-18, 21-22, 27-30).” [1]

Reynolds et al writing in the ‘BMJ’ on glycated haemoglobin note:

“…A loss of red cells reduces the average age of the red cell pool. The glycation of haemoglobin to produce HbA1c occurs over the lifespan of the cells; approximately 50% occurs in days 90-120, and the remainder occurs before this.1 2 HbA1c thus represents a weighted average of the blood glucose concentration over the previous two to three months. In the presence of anaemia, blood loss results in a reduction in the average red cell lifespan and HbA1c is lower than would be expected for the degree of chronic hyperglycaemia. If blood loss is sufficient to shorten average lifespan to 90 days, the HbA1c concentration would theoretically be halved and could give the false impression that glucose control is exemplary…” [2]

In diabetic patients with anaemia (low haemoglobin level), does this need to be corrected before HbA1c is measured again? How long is it necessary to wait before rechecking HbA1c?

We searched the NLH Diabetes Specialist Library and the TRIP and Medline databases but found no guidance or studies to help answer this question. Thus, we can only recommend seeking advice from local specialist. Alternatively, you could call the Diabetes UK Careline:

By telephone
For enquiries to Careline and Careline Scotland:
Telephone: 0845 120 2960, Monday-Friday, 9am-5pm

References
1. NGSP. Factors that interfere with GHB (HbA1c) Test Results. April 2008. (http://www.ngsp.org/prog/factors.htm)
2. Reynolds TM, Smellie WS and Twomey PJ. Glycated haemoglobin (HbA1c) monitoring. BMJ. 2006 Sep 16;333(7568):586-8. (http://www.bmj.com/cgi/content/full/333/7568/586)