A1C level and future risk of diabetes: a systematic review

Evaluation of hemoglobin A1c criteria to assess preoperative diabetes risk in cardiac surgery patients

OBJECTIVE

Hemoglobin A1c (A1C) has recently been recommended for diagnosing diabetes mellitus and diabetes risk (prediabetes). Its performance compared with fasting plasma glucose (FPG) and 2-h post-glucose load (2HPG) is not well delineated. We compared the performance of A1C with that of FPG and 2HPG in preoperative cardiac surgery patients.

METHODS

Data from 92 patients without a history of diabetes were analyzed. Patients were classified with diabetes or prediabetes using established cutoffs for FPG, 2HPG, and A1C. Sensitivity and specificity of the new A1C criteria were evaluated.

RESULTS

All patients diagnosed with diabetes by A1C also had impaired fasting glucose, impaired glucose tolerance, or diabetes by other criteria. Using FPG as the reference, sensitivity and specificity of A1C for diagnosing diabetes were 50% and 96%, and using 2HPG as the reference they were 25% and 95%. Sensitivity and specificity for identifying prediabetes with FPG as the reference were 51% and 51%, respectively, and with 2HPG were 53% and 51%, respectively. One-third each of patients with prediabetes was identified using FPG, A1C, or both. When testing A1C and FPG concurrently, the sensitivity of diagnosing dysglycemia increased to 93% stipulating one or both tests are abnormal; specificity increased to 100% if both tests were required to be abnormal.

CONCLUSIONS

In patients before cardiac surgery, A1C criteria identified the largest number of patients with diabetes and prediabetes. For diagnosing prediabetes, A1C and FPG were discordant and characterized different groups of patients, therefore altering the distribution of diabetes risk. Simultaneous measurement of FGP and A1C may be a more sensitive and specific tool for identifying high-risk individuals with diabetes and prediabetes.

The worldwide epidemiology of type 2 diabetes mellitus--present and future perspectives

Over the past three decades, the number of people with diabetes mellitus has more than doubled globally, making it one of the most important public health challenges to all nations. Type 2 diabetes mellitus (T2DM) and prediabetes are increasingly observed among children, adolescents and younger adults. The causes of the epidemic of T2DM are embedded in a very complex group of genetic and epigenetic systems interacting within an equally complex societal framework that determines behavior and environmental influences. This complexity is reflected in the diverse topics discussed in this Review. In the past few years considerable emphasis has been placed on the effect of the intrauterine environment in the epidemic of T2DM, particularly in the early onset of T2DM and obesity. Prevention of T2DM is a 'whole-of-life' task and requires an integrated approach operating from the origin of the disease. Future research is necessary to better understand the potential role of remaining factors, such as genetic predisposition and maternal environment, to help shape prevention programs. The potential effect on global diabetes surveillance of using HbA(1c) rather than glucose values in the diagnosis of T2DM is also discussed.

Shifting from glucose diagnostic criteria to the new HbA(1c) criteria would have a profound impact on prevalence of diabetes among a high-risk Spanish population

AIM

To investigate changes in the prevalence of diabetes and pre-diabetes by shifting from 2-h plasma glucose and/or fasting plasma glucose diagnostic criteria to the proposed new HbA(1c) -based criteria when applied to a Mediterranean population detected to have a high risk of Type 2 diabetes.

METHODS

Individuals without diabetes aged 45-75 years (n = 2287) were screened using the Finnish Diabetes Risk Score questionnaire, a 2-h oral glucose tolerance test plus HbA(1c) test. Prevalence and degree of diagnostic overlap between three sets of criteria (2-h plasma glucose, fasting plasma glucose and HbA(1c) ) and three diagnostic categories (normal, pre-diabetes and diabetes) were calculated.

RESULTS

Defining diabetes by a single HbA(1c) measurement resulted in a dramatic decrease in prevalence (1.3%), particularly in comparison with diabetes defined by 2-h plasma glucose (8.6%), but was also significant with regard to fasting plasma glucose (2.8%). A total of 201 screened subjects (8.8%) were classified as having diabetes and 1023 (44.7%) as having pre-diabetes based on at least one of these criteria; among these, the presence of all three criteria simultaneously classified only 21 and 110 individuals respectively, about ten percent of each group. The single overlap index between subjects diagnosed as having diabetes by 2-h plasma glucose/fasting plasma glucose vs. HbA(1c) was 13.9/28%. Similarly, the single overlap index regarding pre-diabetes was 19.2/27.1%.

CONCLUSIONS

A shift from the glucose-based diagnosis to the HbA(1c) -based diagnosis for diabetes will reduce diabetes prevalence with a low overall or single degree of overlap between diagnostic categories in this high-risk Spanish population.

HbA1c 5·7-6·4% and impaired fasting plasma glucose for diagnosis of prediabetes and risk of progression to diabetes in Japan (TOPICS 3): a longitudinal cohort study

BACKGROUND

The clinical relevance of the diagnostic criteria for prediabetes to prediction of progression to diabetes has been little studied. We aimed to compare the prevalence of prediabetes when assessed by the new glycated haemoglobin A(1c) (HbA(1c)) 5·7-6·4% criterion or by impaired fasting glucose, and assessed differences in progression rate to diabetes between these two criteria for prediabetes in a Japanese population.

METHODS

Our longitudinal cohort study included 4670 men and 1571 women aged 24-82 years without diabetes at baseline (diabetes was defined as fasting plasma glucose ≥7·0 mmol/L, self-reported clinician-diagnosed diabetes, or HbA(1c) ≥6·5%) who attended Toranomon Hospital (Tokyo, Japan) for a routine health check between 1997 and 2003. Participants with a baseline diagnosis of prediabetes according to impaired fasting glucose (fasting plasma glucose 5·6-6·9 mmol/L) or HbA(1c) 5·7-6·4%, or both, were divided into four groups on the basis of baseline diagnosis of prediabetes. Rate of progression to diabetes was assessed annually.

FINDINGS

Mean follow-up was 4·7 (SD 0·7) years. 412 (7%) of 6241 participants were diagnosed with prediabetes on the basis of the HbA(1c) 5·7-6·4% criterion. Screening by HbA(1c) alone missed 1270 (61%) of the 2092 prediabetic individuals diagnosed by a combination of impaired fasting glucose and HbA(1c) 5·7-6·4%. Overall cumulative probability of progression to diabetes did not differ significantly between participants with prediabetes discordantly diagnosed by either HbA(1c) or impaired fasting glucose alone (incidence was 7% for HbA(1c) alone [n=412 individuals and 30 incident cases] and 9% for impaired fasting glucose alone [n=1270, 108 cases]; log-rank test, p=0·3317). Multivariate-adjusted hazard ratios for incident diabetes were 6·16 (95% CI 4·33-8·77) for those diagnosed with prediabetes by impaired fasting glucose alone and 6·00 (3·76-9·56) for diagnosis by HbA(1c) alone, and were substantially increased to 31·9 (22·6-45·0) for diagnosis by both impaired fasting glucose and HbA(1c) compared with normoglycaemic individuals.

INTERPRETATION

Diagnosis of prediabetes by both the new HbA(1c) criterion and impaired fasting glucose identified individuals with an increased risk of progression to diabetes. Although the new HbA(1c) criterion identified fewer individuals at high risk than did impaired fasting glucose, the predictive value for progression to diabetes assessed by HbA(1c) 5·7-6·4% was similar to that assessed by impaired fasting glucose alone. The two tests used together could efficiently target people who are most likely to develop diabetes and allow for early intervention.

FUNDING

Japan Society for the Promotion of Science; Ministry of Health Labor and Welfare, Japan.

The general use of glycated haemoglobin for the diagnosis of diabetes and other categories of glucose intolerance: still a long way to go

Glycated haemoglobin (HbA(1c)) is considered the 'gold standard' for monitoring metabolic control in diabetes. An International Expert Committee recently recommended HbA(1c) as a better method than measurement of glucose to use in the diagnosis of diabetes, based on its strong association with microvascular complications, a lower day-to-day variability and ease of use, not necessarily in the fasting state. These recommendations have been embraced by the American Diabetes Association (ADA), which stated in its Standards of Medical Care in Diabetes 2010 that "A(1c), fasting plasma glucose or the 2 h 75 g oral glucose tolerance test (OGTT) are appropriate for testing diabetes and assessing the risk of future diabetes," and that "a confirmed A(1c) ≥ 6.5% is diagnostic for diabetes." Measuring HbA(1c) has several advantages over glucose measurements, but its exclusive use should only be considered if the test is conducted under standardised conditions and its limitations are taken into due account. The impact of its use on the epidemiology of diabetes and other categories of glucose intolerance, as seen from recent reports, is also discussed.

Glycated hemoglobin predicts all-cause, cardiovascular, and cancer mortality in people without a history of diabetes undergoing coronary angiography

OBJECTIVE

Glycated hemoglobin has been suggested to be superior to fasting glucose for the prediction of vascular disease and death from any cause. The aim of the present work was to analyze and compare the predictive value of glycated hemoglobin and fasting glucose on all-cause and cause-specific mortality in subjects who underwent coronary angiography.

RESEARCH DESIGN AND METHODS

We studied 2,686 participants of the Ludwigshafen Risk and Cardiovascular health study without a history of diabetes. The majority of this cohort had coronary artery disease. Glycated hemoglobin was measured at the baseline examination. The mean (± SD) duration of the follow-up for all-cause, cardiovascular, and cancer mortality was 7.54 ± 2.1 years.

RESULTS

A total of 508 deaths occurred during the follow-up. Of those, 299 were accounted for by cardiovascular diseases and 79 by cancer. Baseline glycated hemoglobin was predictive of all-cause, cardiovascular, and cancer mortality. The multivariable-adjusted hazard ratios (HR) (95% CI) for glycated hemoglobin values of <5.0, 5.0-5.4, 5.5-5.9, 6.0-6.4, 6.5-7.4, and ≥7.5% for all-cause mortality were 1.36 (0.85-2.18), 1.00 (0.76-1.32), 1.00 (reference), 1.11 (0.88-1.41), 1.39 (1.07-1.82), and 2.15 (1.32-3.53), respectively. Similar J-shaped relationships were found between glycated hemoglobin and cardiovascular and cancer mortality. The associations of glycated hemoglobin with all-cause and cardiovascular mortality remained significant after inclusion of fasting glucose as a covariate. However, fasting glucose was not significantly related to mortality when adjusting for glycated hemoglobin.

CONCLUSIONS

Glycated hemoglobin significantly and independently of fasting glucose predicts all-cause and cardiovascular mortality in whites at intermediate to high cardiovascular risk.

Outcomes in women with a history of gestational diabetes. Screening and prevention of type 2 diabetes. Literature review

Women with a history of gestational diabetes mellitus (GDM) are characterized by a high risk of type 2 diabetes mellitus (T2DM) (x 7), metabolic syndrome (x 2 to 5) and cardiovascular diseases (x 1,7). Women with lesser degrees of glucose intolerance share the same risks. T2DM may occur from post-partum (5 to 14%) to several years later, up to 25 years. Some factors associated with T2DM are identified: obesity, early diagnosis of GDM before 24 weeks gestation, high pregnancy OGTT blood glucose or insulin-therapy during GDM. Screening for T2DM only with fasting glucose provides less sensibility than with OGTT; HbA1c may supplant these dosages. The recurrence rate of GDM is between 30 and 84%, non-white ethnicity and insulinotherapy during GDM being the best proven predictors. High risk women need repeated life-long screenings for glycaemic abnormalities, or when another pregnancy is planned. Among obese women with history of GDM who show minor glycoregulation disturbances, modifications of lifestyle in intensive programs or metformin halve the risk of DT2. However, studies analysing practices show low adhesion to screening; without an intensive program, few women implement lifestyle modifications. These intensive programs should be implemented and proposed to high-risk women. Their therapeutic education should also include prevention of cardiovascular risk factors.

[Outcomes in women with history of gestational diabetes mellitus. Screening and prevention of type 2 diabetes mellitus. Literature review]

Women with a history of gestational diabetes mellitus (GDM) are characterized by a high risk of type 2 diabetes mellitus (T2DM) (X 7), metabolic syndrome (X 2 to 5) and cardiovascular diseases (X 1,7). Women with lesser degrees of glucose intolerance share the same risks. T2DM may occur from postpartum (5 to 14%) to several years later, up to 25 years. Some factors associated with T2DM are identified: obesity, early diagnostic before 24 weeks, high pregnancy OGTT blood glucose or insulinotherapy. Screening for T2DM only with fasting glucose provides less sensibility than with OGTT; HbA1c may supplant these dosages. The recurrence rate of GDM is between 30 and 84%, non-white ethnicity and insulinotherapy during GDM being the best proven predictors. High risk women need repeated life-long screenings for glycemic abnomalies, or when another pregnancy is planned. Among overweight or obese women with history of GDM who show minor glycoregulation disturbances, it is proved that modifications of lifestyle in intensive programs or metformin halve the risk of DT2. However, studies analysing practices show low adhesion to screening; without an intensive program, few women implement lifestyle modifications. These intensive programs should be implemented and proposed to high-risk women. Their therapeutic education should also include prevention of cardiovascular risk factors.