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)

Are the use of statins associated with an increase in diabetes?

 

A 2010 paper in the Lancet [1] reports:

«FINDINGS: We identified 13 statin trials with 91 140 participants, of whom 4278 (2226 assigned statins and 2052 assigned control treatment) developed diabetes during a mean of 4 years. Statin therapy was associated with a 9% increased risk for incident diabetes (odds ratio [OR] 1.09; 95% CI 1.02-1.17), with little heterogeneity (I(2)=11%) between trials. Meta-regression showed that risk of development of diabetes with statins was highest in trials with older participants, but neither baseline body-mass index nor change in LDL-cholesterol concentrations accounted for residual variation in risk. Treatment of 255 (95% CI 150-852) patients with statins for 4 years resulted in one extra case of diabetes.

INTERPRETATION: Statin therapy is associated with a slightly increased risk of development of diabetes, but the risk is low both in absolute terms and when compared with the reduction in coronary events. Clinical practice in patients with moderate or high cardiovascular risk or existing cardiovascular disease should not change.»

This article was reviewed by the National Prescribing Centre [2], which reported:

«The results of this meta-analysis show that patients taking statins were at slightly increased risk of diabetes compared with those not taking statins, and this risk seemed higher in older patients. The results only show that statins were associated with an increased risk of diabetes, not that they caused this (although this is a possibility) and the association may be due to residual confounding factors. Also, we don’t know from this study if any increase risk of developing diabetes resulted in a detrimental effect on patient-oriented outcomes, i.e. did them developing diabetes prevent them living longer or better?

Whatever the cause, in absolute terms, the increased risk of diabetes is small, especially in relation to the reduction in cardiovascular events seen with statins. In this meta-analysis, one additional case of diabetes was seen per 255 patients taking statins for four years. The authors calculated that, using data from the Cholesterol Treatment Trialists (CTT) meta-analysis of statin trials in 71,370 non-diabetic patients, statins are associated with a reduction in major coronary events of 5.4 events per 255 patients treated for four years (this is compared with control therapy for a 1mmol/L reduction in LDL-cholesterol).

In view of the evidence for benefit with statins, the authors argue that the small excess risk of incident diabetes is favourably balanced by cardiovascular benefit. Therefore, these results should not change clinical decision making in patients for whom statins are indicated. NICE guidance on lipid modification states that statins should be offered to people with clinical evidence of CVD, or a 20% or greater 10-year risk of developing this; and this guidance remains appropriate. For patients at lower cardiovascular risk or in patient groups in which cardiovascular benefit has not been proven, the potentially raised risk of diabetes should be taken into account if statin therapy is considered.

The authors recommend that the development of diabetes should be specified as a secondary endpoint in future large statin trials. They also suggest that screening for diabetes might be useful in patients taking statins, particularly older patients, and this would seem to be sensible advice.»

References

1) http://www.ncbi.nlm.nih.gov/pubmed/20167359?dopt=AbstractPlus

2) http://www.npci.org.uk/blog/?p=1098