Differences in A1C by race and ethnicity among patients with impaired glucose tolerance in the Diabetes Prevention Program

HbA1c for diagnosis of type 2 diabetes. Is there an optimal cut point to assess high risk of diabetes complications, and how well does the 6.5% cutoff perform?

Glycated hemoglobin (HbA1c) has recently been recommended for the diagnosis of type 2 diabetes mellitus (T2DM) by leading diabetes organizations and by the World Health Organization. The most important reason to define T2DM is to identify subjects with high risk of diabetes complications who may benefit from treatment. This review addresses two questions: 1) to assess from existing studies whether there is an optimal HbA1c threshold to predict diabetes complications and 2) to assess how well the recommended 6.5% cutoff of HbA1c predicts diabetes complications. HbA1c cutoffs derived from predominantly cross-sectional studies on retinopathy differ widely from 5.2%-7.8%, and among other reasons, this is due to the heterogeneity of statistical methods and differences in the definition of retinopathy. From the few studies on other microvascular complications, HbA1c thresholds could not be identified. HbA1c cutoffs make less sense for the prediction of cardiovascular events (CVEs) because CVE risks depend on various strong risk factors (eg, hypertension, smoking); subjects with low HbA1c levels but high values of CVE risk factors were shown to be at higher CVE risk than subjects with high HbA1c levels and low values of CVE risk factors. However, the recommended 6.5% threshold distinguishes well between subjects with and subjects without retinopathy, and this distinction is particularly strong in severe retinopathy. Thus, in existing studies, the prevalence of any retinopathy was 2.5 to 4.5 times as high in persons with HbA1c-defined T2DM as in subjects with HbA1c <6.5%. To conclude, from existing studies, a consistent optimal HbA1c threshold for diabetes complications cannot be derived, and the recommended 6.5% threshold has mainly been brought about by convention rather than by having a consistent empirical basis. Nevertheless, the 6.5% threshold is suitable to detect subjects with prevalent retinopathy, which is the most diabetes specific complication. However, most of the studies on associations between HbA1c and microvascular diabetes complications are cross-sectional, and there is a need for longitudinal studies.

Impact of HbA1c criterion on the definition of glycemic component of the metabolic syndrome: the China health and nutrition survey 2009

BACKGROUND

In 2009, a unified definition of metabolic syndrome (MetS) was proposed, of which, the glycemic component is defined on the basis of fasting plasma glucose (FPG) level. Recently, the American Diabetes Association (ADA) recommended the use of glycated hemoglobin (HbA1c) as an alternative to FPG to define prediabetes. Hence, we aim to compare the performance of HbA1c and FPG in the definition of glycemic component of the MetS among Chinese adults.

METHODS

We conducted a cross-sectional analysis of 7641 Chinese participants aged ≥18 years using data from the China Health and Nutrition Survey 2009. MetS was defined according to the consensus criteria in 2009. We compared the use of HbA1c versus FPG in the definition of the glycemic component of MetS. Increased HbA1c value was defined following the criterion of HbA1c cut-off point of ≥5.7% recommended by the ADA.

RESULTS

Overall, 1136 (14.9%) had MetS according to FPG ≥ 5.6 mmol/l, and 1640 (21.5%) had MetS according to HbA1c ≥ 5.7%. Compared with individuals with FPG-based diagnosis of MetS, individuals with HbA1c-based diagnosis of MetS were older, had higher levels of LDL-C, magnesium, and transferrin, and lower levels of uric acid. Of those found to have MetS according to either FPG or HbA1c (n = 2008), overlap between HbA1c- and FPG-based diagnosis of MetS was limited (n = 768, 38.2%). The overlap index regarding MetS diagnosed by FPG or HbA1c persisted low in each evaluated subgroup (≤ 50.0%).

CONCLUSIONS

We note limited overlap and poor agreement between FPG- and HbA1c-based diagnosis of MetS. Screening MetS through introduction of HbA1c in addition to FPG could contribute to identification of more people with MetS.

ATLANTIC DIP: simplifying the follow-up of women with previous gestational diabetes

OBJECTIVE

Previous gestational diabetes (GDM) is associated with a significant lifetime risk of type 2 diabetes. In this study, we assessed the performance of HbA1c and fasting plasma glucose (FPG) measurements against that of 75 g oral glucose tolerance testing (OGTT) for the follow-up screening of women with previous GDM.

METHODS

Two hundred and sixty-six women with previous GDM underwent the follow-up testing (mean of 2.6 years (s.d. 1.0) post-index pregnancy) using HbA1c (100%), and 75 g OGTT (89%) or FPG (11%). American Diabetes Association (ADA) criteria for abnormal glucose tolerance were used.

DESIGN, COHORT STUDY, AND RESULTS

The ADA HbA1c high-risk cut-off of 39 mmol/mol yielded sensitivity of 45% (95% CI 32, 59), specificity of 84% (95% CI 78, 88), negative predictive value (NPV) of 87% (95% CI 82, 91) and positive predictive value (PPV) of 39% (95% CI 27, 52) for detecting abnormal glucose tolerance. ADA high-risk criterion for FPG of 5.6 mmol/l showed sensitivity of 80% (95% CI 66, 89), specificity of 100% (95% CI 98, 100), NPV of 96% (95% CI 92, 98) and PPV of 100% (95% CI 91, 100). Combining HbA1c ≥39 mmol/mol with FPG ≥5.6 mmol/l yielded sensitivity of 90% (95% CI 78, 96), specificity of 84% (95% CI 78, 88), NPV of 97% (95% CI 94, 99) and PPV of 56% (95% CI 45, 66).

CONCLUSIONS

Combining test cut-offs of 5.6 mmol/l and HbA1c 39 mmol/mol identifies 90% of women with abnormal glucose tolerance post-GDM (mean 2.6 years (s.d.1.0) post-index pregnancy). Applying this follow-up strategy will reduce the number of OGTT tests required by 70%, will be more convenient for women and their practitioners, and is likely to lead to increased uptake of long-term retesting by these women whose risk for type 2 diabetes is substantially increased.

Use of glycosylated hemoglobin increases diabetes screening for at-risk adolescents in primary care settings

OBJECTIVE

To examine rates of diabetes screening in obese adolescents in an ethnically diverse primary care health care system before and after an internal recommendation to use HbA1c-based screening.

RESEARCH DESIGN AND METHODS

Adolescents 12-18-years old with BMI > 95% were identified through electronic medical record review during two 18-month periods in 8 community health clinics and 13 school-based health centers: period 1 (P1, 19 April 2008 to 19 October 2009) and period 2 (P2, 3 May 2010 to 3 November 2011). Testing for diabetes in the 2 yr preceding the most recently elevated BMI was reviewed.

RESULTS

A total of 2870 obese adolescents were identified in P1 and 3940 in P2. Ethnicity was primarily Hispanic, with smaller populations of Black and White youth. The percent of obese teens screened for diabetes increased from 40% in P1 to 47% in P2. Use of HbA1c increased 493% during P2. Older teens (>15 yr), those seen during P2, and those with BMI ≥ 30 kg/m2 were more likely to be screened. Record review confirmed equal rates of type 2 diabetes in the two periods: 8 incident (0.7%) cases in P1 and 13 (0.7%) in P2.

CONCLUSIONS

The use of HbA1c, a non-fasting and logistically simpler test, was associated with increased diabetes screening in primary care. The percentage of screened patients with confirmed type 2 diabetes remained unchanged. Thus, despite potential pitfalls, the use of HbA1c for screening appears to be as successful as previous approaches in identifying adolescents with diabetes.

Hemoglobin A1c, fasting plasma glucose, and 2-hour plasma glucose distributions in U.S. population subgroups: NHANES 2005-2010

PURPOSE

Although mean concentrations of hemoglobin A1c (A1C), fasting plasma glucose, and 2-hour plasma glucose differ by demographics, it is unclear what other characteristics of the distributions may differ, such as the amount of asymmetry of the distribution (skewness) and shift left or right compared with another distribution (shift).

METHODS

Using kernel density estimation, we created smoothed plots of the distributions of fasting plasma glucose (N = 7250), 2-hour plasma glucose (N = 5851), and A1C (N = 16,209) by age, race-ethnicity, and sex in the 2005-2010 National Health and Nutrition Examination Survey, a nationally representative sample of U.S. adults including people with and without diabetes. We tested differences in distributions using cumulative logistic regression.

RESULTS

The distributions were generally unimodal and right-skewed. All distributions were shifted higher and more right-skewed for older age groups (P < .001 for each marker). Compared with non-Hispanic whites, the distribution of fasting plasma glucose was shifted higher for Mexican-Americans (P = .01), whereas the distribution of A1C was shifted higher for non-Hispanic blacks (P < .001). The distribution of fasting plasma glucose was shifted higher for men (P < .001) and the distribution of 2-hour plasma glucose was shifted higher for women (P = .01).

CONCLUSIONS

We provide a graphic reference for comparing these distributions and diabetes cut-points by demographic factors.

Combining glycosylated hemoglobin A1c and fasting plasma glucose for diagnosis of type 2 diabetes in Chinese adults

BACKGROUND

Glycosylated hemoglobin A1c (HbA1c) has been applied to identify type 2 diabetes (T2DM) in the U.S. and European countries. It has not been used in China mainly due to lack of a standardized approach to measure HbA1c, short of knowledge about racial-specific standard and deficiency of an optimal cut-off point.

METHODS

To evaluate combination of HbA1c and fasting plasma glucose (FPG) in diagnosing T2DM in Chinese adults, a multistage sampling cross-sectional study was conducted in Shanghai, China, in 2009. The FPG measurement, HbA1c assay, and oral glucose tolerance test (OGTT) were performed in 6,661 Chinese adults (3057 men, 3604 women) who had no prior history of diabetes to identify the unrecognized T2DM.

RESULTS

A total of 454 participants were identified as T2DM based on the 1999 World Health Organization (WHO) diagnostic criteria. Of these patients, 239 were detected using an FPG ≥ 7.0 mmol/l and 141 were further identified using an HbA1c ≥ 43 mmol/mol (6.1%), achieving a sensitivity of 83.7% and a specificity of 89.3% for combining use of FPG and HbA1c. In subjects at high risk of diabetes, the combining use of FPG and HbA1c produced a higher sensitivity and an improved positive predictive value (PPV), and had a satisfactory specificity and negative predictive value (NPV).

CONCLUSIONS

The combining use of FPG and HbA1c is a potential screening and diagnosis approach for T2DM in Chinese adults, especially among those at high risk of the disease.

Biological variation of cardiovascular risk factors in patients with diabetes

Biological variation refers to the natural fluctuations found when repeated measurements are made in a biological system. Generally, biological variation remains within narrow boundaries in health, but may differ in pathological states, with implications for the diagnosis and monitoring of disease processes. In disease, biological variation may alter such that any subsequent measurement may need to have a greater difference compared with a healthy control to be biologically relevant. Treatments such as insulin or anti-hypertensive therapy have been shown to reduce biological variability closer to normal levels and theoretically this may help prevent complication development or progression in conditions such as diabetes. This article reviews how biological variation can influence our identification and assessment of vascular risk factors in a person with diabetes. The role of biological variation in the diagnosis of diabetes (glucose and HbA1c) is then examined. Finally, the influence that common treatments in diabetes have in modifying biological variation is described.

Race/ethnicity disparities in dysglycemia among U.S. women of childbearing age found mainly in the nonoverweight/nonobese

OBJECTIVE

To describe the burden of dysglycemia-abnormal glucose metabolism indicative of diabetes or high risk for diabetes-among U.S. women of childbearing age, focusing on differences by race/ethnicity.

RESEARCH DESIGN AND METHODS

Using U.S. National Health and Nutrition Examination Survey data (1999-2008), we calculated the burden of dysglycemia (i.e., prediabetes or diabetes from measures of fasting glucose, A1C, and self-report) in nonpregnant women of childbearing age (15-49 years) by race/ethnicity status. We estimated prevalence risk ratios (PRRs) for dysglycemia in subpopulations stratified by BMI (measured as kilograms divided by the square of height in meters), using predicted marginal estimates and adjusting for age, waist circumference, C-reactive protein, and socioeconomic factors.

RESULTS

Based on data from 7,162 nonpregnant women, representing>59,000,000 women nationwide, 19% (95% CI 17.2-20.9) had some level of dysglycemia, with higher crude prevalence among non-Hispanic blacks and Mexican Americans vs. non-Hispanic whites (26.3% [95% CI 22.3-30.8] and 23.8% [19.5-28.7] vs. 16.8% [14.4-19.6], respectively). In women with BMI<25 kg/m2, dysglycemia prevalence was roughly twice as high in both non-Hispanic blacks and Mexican Americans vs. non-Hispanic whites. This relative increase persisted in adjusted models (PRRadj 1.86 [1.16-2.98] and 2.23 [1.38-3.60] for non-Hispanic blacks and Mexican Americans, respectively). For women with BMI 25-29.99 kg/m2, only non-Hispanic blacks showed increased prevalence vs. non-Hispanic whites (PRRadj 1.55 [1.03-2.34] and 1.28 [0.73-2.26] for non-Hispanic blacks and Mexican Americans, respectively). In women with BMI>30 kg/m2, there was no significant increase in prevalence of dysglycemia by race/ethnicity category.

CONCLUSIONS

Our findings show that dysglycemia affects a significant portion of U.S. women of childbearing age and that disparities by race/ethnicity are most prominent in the nonoverweight/nonobese.

Prevalence of Diabetes and Prediabetes according to Fasting Plasma Glucose and HbA1c

BACKGROUND

Due to the inconvenience of performing oral glucose tolerance tests and day to day variability in glucose level, glycated hemoglobin (HbA1c) has been recommended by the American Diabetes Association as a method to diagnose diabetes. In addition, the Korean Diabetes Association has also recommended the use of HbA1c as a diagnostic test for diabetes. In this study, we evaluated the prevalence of diabetes according to fasting plasma glucose (FPG) level only or the combination of FPG and HbA1c tests.

METHODS

Data from the 2011 Korea National Health and Nutrition Examination Survey (KNHANES) were analyzed. Among 5,811 subjects aged 30 years or older, 5,020 were selected after excluding the data of fasting time <8 hours, missing values from fasting glucose or HbA1c level, previous diagnosis of diabetes made by physicians, or current use of antidiabetic medications. Diabetes was defined as FPG ≥126 mg/dL, previous diagnosis of diabetes made by a medical doctor, current use of antidiabetic medications, and/or HbA1c ≥6.5%. Prediabetes was defined as FPG of 100 to 125 mg/dL and/or HbA1c of 5.7% to 6.4%.

RESULTS

When we used FPG only, the prevalence of diabetes and prediabetes were 10.5% (men, 12.6%; women, 8.5%) and 19.3% (men, 23.8%; women, 14.9%), respectively. When HbA1c was included as a diagnostic test, the prevalence of diabetes and prediabetes increased to 12.4% (men, 14.5%; women, 10.4%) and 38.3% (men, 41%; women, 35.7%), respectively. Participants with HbA1c ≥6.5% and fasting glucose level <126 mg/dL were older and had lower estimated glomerular filtration rate.

CONCLUSION

We concluded that using fasting glucose level only may result in an underestimation of diabetes and prediabetes. HbA1c is an acceptable complementary diagnostic test for diabetes in Korean patients. However, national standardization is needed to order to use HbA1c as a diagnostic method of diabetes and prediabetes.

No racial differences in the association of glycated hemoglobin with kidney disease and cardiovascular outcomes

OBJECTIVE

There is debate regarding the clinical significance of well-established racial differences in HbA1c. We compared the associations of diabetes diagnostic categories for HbA1c and fasting glucose with clinical outcomes in black and white persons in the community.

RESEARCH DESIGN AND METHODS

We conducted a prospective cohort analysis of participants without diabetes or cardiovascular disease from the Atherosclerosis Risk in Communities study. We examined the associations of clinical categories of HbA1c (<5.7%, 5.7-6.4%, ≥6.5%) and fasting glucose (<100, 100-125, ≥126 mg/dL) with outcomes separately among 2,484 black and 8,593 white participants and tested for race interactions.

RESULTS

Baseline characteristics differed significantly in blacks compared with whites, including HbA1c (5.8 vs. 5.4%; P<0.001). During 18 years of follow-up, there were trends of increased risk of kidney disease, fatal and nonfatal coronary heart disease, and stroke across categories of HbA1c in both blacks and whites. The adjusted hazard ratios for each outcome across categories of HbA1c were similar in blacks and whites (P for interaction>0.05) except for all-cause mortality. Patterns of association were similar, but weaker, for fasting glucose. HbA1c and fasting glucose both were more strongly associated with all-cause mortality in whites compared with blacks, largely explained by racial differences in the rate of cardiovascular deaths.

CONCLUSIONS

HbA1c is a risk factor for vascular outcomes and mortality in both black and white adults. Patterns of association for HbA1c were similar to or stronger than those for fasting glucose. With respect to long-term outcomes, our findings support a similar interpretation of HbA1c in blacks and whites for diagnosis and treatment of diabetes mellitus.

Ethnic differences in glycemic markers in patients with type 2 diabetes

OBJECTIVE

Recent studies have reported hemoglobin A1c (HbA1c) differences across ethnic groups that could limit its use in clinical practice. The authors of the A1C-Derived Average Glucose study have advocated to report HbA1c in estimated average glucose (AG) equivalents. The aim of this study was to assess the relationships between HbA1c and the mean of three 7-point self-monitored blood glucose (BG) profiles, and to assess whether estimated AG is an accurate measure of glycemia in different ethnic groups.

RESEARCH DESIGN AND METHODS

We evaluated 1,879 participants with type 2 diabetes in the DURABLE trial who were 30 to 80 years of age, from 11 countries, and, according to self-reported ethnic origin, were Caucasian, of African descent (black), Asian, or Hispanic. We performed logistic regression of the relationship between the mean self-monitored BG and HbA1c, and estimated AG, according to ethnic background.

RESULTS

Baseline mean (SD) HbA1c was 9.0% (1.3) (75 [SD, 14] mmol/mol), and mean self-monitored BG was 12.1 mmol/L (3.1) (217 [SD, 55] mg/dL). In the clinically relevant HbA1c range of 7.0-9.0% (53-75 mmol/mol), non-Caucasian ethnic groups had 0.2-0.5% (2-6 mmol/mol) higher HbA1c compared with Caucasians for a given BG level. At the mean self-monitored BG levels≤11.6 mmol/L, estimated AG overestimated the actual average BG; at levels>11.6 mmol/L, estimated AG underestimated the actual BG levels.

CONCLUSIONS

For a given degree of glycemia, HbA1c levels vary among different ethnic groups. Ethnicity needs to be taken into account when using HbA1c to assess glycemic control or to set glycemic targets. Estimated AG is not a reliable marker for mean glycemia and therefore is of limited clinical value.

HbA1c and the diagnosis of diabetes and prediabetes in a middle-aged and elderly Han population from northwest China (HbA1c)

OBJECTIVE

To identify the optimal threshold of HbA1c and to evaluate the predictive performance of HbA1c levels in diagnosing diabetes and prediabetes in a middle-aged and elderly Han Chinese population from northwest China.

METHODS

In all, 3354 participants aged ≥ 40 years with no history of diabetes from northwest China were enrolled in the present cross-sectional study. All subjects underwent a 75-g oral glucose tolerance test (OGTT), as well as HbA1c testing. HbA1c thresholds for diagnosing diabetes and prediabetes were identified by the highest sum of sensitivity and specificity of each cut-off point, and the receiver operating characteristic (ROC) curve was used to evaluate the diagnostic accuracy of the HbA1c threshold.

RESULTS

The mean (± SD) age of the participants was 57 ± 8 years, and 70.75% were women. Based on results of the OGTT, 1347 (40.16%) subjects had impaired fasting glucose and/or impaired glucose tolerance, and 725 (21.62%) had diabetes. The area under the ROC curve for detecting undiagnosed diabetes and prediabetes by HbA1c levels was 0.810 (95% confidence interval [CI] 0.796-0.823) and 0.732 (95% CI 0.717-0.747), respectively. HbA1c threshold of 6.4% and 6.1% produced the highest sum of sensitivity (60.00% and 61.49%) and specificity (87.33% and 73.24%) for diagnosing diabetes and prediabetes, respectively.

CONCLUSION

HbA1c is an effective and convenient method for diagnosing diabetes and prediabetes. HbA1c thresholds of 6.4% and 6.1% may be used as diagnostic criteria for diabetes and prediabetes, respectively, in the Han Chinese population living in northwest China.

Racial differences in HbA1c: a cross-sectional analysis of a Brazilian public primary care population

BACKGROUND

Blacks show higher levels of HbA1c in studies with different populations and are disproportionately affected by most diabetes-related complications.

AIMS

The study aims to investigate if the prevalence of altered glycated hemoglobin (HbA1c) varies with skin color and if there is a familial aggregation of either skin color and HbA1c.

METHODS

The study used the CAMELIA study (Cardio-Metabolic-Renal familiar) population, conducted between June 2006 and December 2007 (cross sectional). Families were recruited from 13 Family Doctor Program Unities of Niteroi, Brazil, a highly miscegenated population. The visits included questionnaire, medical consultation, anthropometric and nutritional assessment. Blood pressure, blood/urine samples were collected. The dosage of HbA1c was performed by immunoturbidimetry in Labmax 240 equipment.

RESULTS

We compare data of 241 (25.5%) Blacks, versus 422 (44.7%) Mulattos or 272 (28.8%) Whites. The groups did not differ significantly with regard to most measures. Blacks had the lowest levels of income/education, higher frequency of diabetes and hypertension (p<0.20) as higher levels of HbA1c (p<0.05) that persisted after adjusting for possible confounders. Among blacks, the correlations between siblings of HbA1c were higher than among white/mulatto, reaching 86% versus 50%, respectively.

CONCLUSION

Those results indicate that Brazilian Blacks patients must have more attention, focusing on diabetes preventive care. Longitudinal studies are needed to address the question if the altered level of HbA1c has a real clinical impact.

Multicenter evaluation of hemoglobin A1c assay on capillary electrophoresis

BACKGROUND

Hemoglobin A1c (HbA1c) measurement is currently used for the routine monitoring of long-term glycemic status, thus playing a fundamental role in the management of this disease. Since this marker has recently been recommended as an additional tool for diagnosing diabetes, it's of the utmost importance to ensure that the precision and accuracy of HbA1c methods are satisfactory.

METHODS

We assessed the analytical performances of the Capillarys 2 Flex Piercing® analyzer and compared the results obtained with those from two other widely used HPLC instruments. Furthermore, we evaluated the convenience and ergonomics of the system in authentic routine work conditions in three centers.

RESULTS

Within-laboratory (n=40) and between-laboratory (n=120) imprecision CV% using four blood samples with different concentrations of HbA1c were <3.4% and <3.1% using IFCC units and <2.1% and <2.0% using NGSP units, respectively. The obtained trueness (<3 mmol/mol, <0.3%) was highly satisfactory, nor was HbA1c measurement compromised by the presence of the commonly present hemoglobinopathies. The comparison made with established methods revealed excellent agreement (r>0.985).

CONCLUSIONS

The evaluated method is precise, accurate and robust, with a high throughput. It also allows the identification of the most frequent Hb variants and therefore may be a valid alternative to other methods currently proposed for routine use in clinical laboratories.

Cardiometabolic health among gastric bypass surgery patients with polycystic ovarian syndrome

AIM: To examine the effect of gastric bypass surgery on cardiometabolic health among women with polycystic ovarian syndrome (PCOS).

METHODS: Retrospective medical chart review identified women (n = 389) with PCOS who underwent Roux-en-Y gastric bypass surgery from 2001-2009 in one surgical practice. Separate repeated measures linear mixed models were fit using the MIXED procedure to assess mean change in cardiometabolic disease risk factors from before to 1-year after surgery and were evaluated by ethnicity [Hispanic, non-Hispanic black (NHB) and white (NHW)].

RESULTS: The majority of the sample was Hispanic (66%, 25% NHB, 9% NHW). Mean body mass index significantly improved 1 year post-surgery for all ethnic groups (45.5 to 35.5 kg/m² for Hispanics, 46.8 to 37.7 kg/m² for NHB and 45.7 to 36.7 kg/m² for NHW, P < 0.001). Among Hispanic women mean total cholesterol (198.1 to 160.2 mg/dL), low-density lipoproteins (LDL) cholesterol (120.9 to 91.0 mg/dL), triglycerides (148.6 to 104.8 mg/dL), hemoglobin A1c (6.2% to 5.6%), alanine aminotransferase (28.1 to 23.0 U/L) and aspartate aminotransferase (23.5 to 21.6 U/L) decreased significantly (P < 0.001). Among NHB, mean total cholesterol (184.5 to 154.7 mg/dL), LDL cholesterol (111.7 to 88.9 mg/dL) and triglycerides (99.7 to 70.0 mg/dL) decreased significantly (P < 0.05). Among NHW, mean total cholesterol (200.9 to 172.8 mg/dL) and LDL cholesterol (124.2 to 96.6 mg/dL), decreased significantly (P < 0.05). Pairwise ethnic group comparisons of all cardiometabolic outcomes adjusted for age and type of surgery before and 1 year after surgery showed no statistical difference between the three groups for any outcome.

CONCLUSION: Cardiometabolic disease risk improvements vary by ethnicity and obesity may impact glucose tolerance and liver function changes more in Hispanic women with PCOS vs non-Hispanic women.

Hemoglobin a1c is positively correlated with framingham risk score in older, apparently healthy nondiabetic korean adults

BACKGROUND

Several studies have suggested that elevated levels of hemoglobin A1c (HbA1c) are associated with cardiovascular disease (CVD) in nondiabetic individuals. However, it is unclear whether HbA1c levels can serve as a simple screening marker for increased CVD risk in nondiabetic individuals. Our objective was to evaluate the relationship between HbA1c levels and CVD risk using the Framingham risk score (FRS) in older, apparently healthy nondiabetic Korean adults.

METHODS

We retrospectively studied 2,879 Korean adults between the ages of 40 and 79 who underwent voluntary health check-ups at the Health Promotion Center of our hospital from July 2009 to June 2011. Subjects were subdivided based on their HbA1c levels into four groups: tertiles within the HbA1c normal tolerance range and a group for subjects with an increased risk for diabetes (IRD).

RESULTS

The mean FRS for the upper tertile (9.6±3.8) group was significantly higher than that of the middle tertile (8.4±4.0) and lower tertile (7.6±3.8) groups. In addition, FRS was highest in the IRD group (10.5±3.7). Multiple linear regression analysis demonstrated that HbA1c levels exhibited a significant positive correlation with FRS when adjusted for confounding variables in all subjects (β±standard error [SE], 0.018±0.002; R (2), 0.131), women (β±SE, 0.023±0.003; R (2), 0.170), and men (β±SE, 0.016±0.004; R (2), 0.109).

CONCLUSION

HbA1c levels were positively correlated with FRS in older, apparently healthy nondiabetic Korean adults. We propose that HbA1c levels may reflect CVD risk in nondiabetic individuals.

Influence of adiposity on insulin resistance and glycemia markers among U.K. Children of South Asian, black African-Caribbean, and white European origin: child heart and health study in England

OBJECTIVE

Ethnic differences in type 2 diabetes risk between South Asians and white Europeans originate before adult life and are not fully explained by higher adiposity levels in South Asians. Although metabolic sensitivity to adiposity may differ between ethnic groups, this has been little studied in childhood. We have therefore examined the associations among adiposity, insulin resistance, and glycemia markers in children of different ethnic origins.

RESEARCH DESIGN AND METHODS

Cross-sectional study of 4,633 9- to 10-year-old children (response rate 68%) predominantly of South Asian, black African-Caribbean, and white European origin (n = 1,266, 1,176, and 1,109, respectively) who had homeostasis model assessments of insulin resistance (HOMA-IR), glycemia markers (HbA1c and fasting glucose), and adiposity (BMI, waist circumference, skinfold thicknesses, and bioimpedance [fat mass]).

RESULTS

All adiposity measures were positively associated with HOMA-IR in all ethnic groups, but associations were stronger among South Asians compared to black African-Caribbeans and white Europeans. For a 1-SD increase in fat mass percentage, percentage differences in HOMA-IR were 37.5% (95% CI 33.3-41.7), 29.7% (25.8-33.8), and 27.0% (22.9-31.2), respectively (P interaction < 0.001). All adiposity markers were positively associated with HbA1c in South Asians and black African-Caribbeans but not in white Europeans; for a 1-SD increase in fat mass percentage, percentage differences in HbA1c were 0.04% (95% CI 0.03-0.06), 0.04% (0.02-0.05), and 0.02% (-0.00 to 0.04), respectively (P interaction < 0.001). Patterns for fasting glucose were less consistent.

CONCLUSIONS

South Asian children are more metabolically sensitive to adiposity. Early prevention or treatment of childhood obesity may be critical for type 2 diabetes prevention, especially in South Asians.

Use of hemoglobin A1C to detect Haitian-Americans with undiagnosed Type 2 diabetes

OBJECTIVE

To evaluate the validity of hemoglobin A1C (A1C) as a diagnostic tool for type 2 diabetes and to determine the most appropriate A1C cutoff point for diagnosis in a sample of Haitian-Americans.

SUBJECTS AND METHODS

Subjects (n = 128) were recruited from Miami-Dade and Broward counties, FL. Receiver operating characteristics (ROC) analysis was run in order to measure sensitivity and specificity of A1C for detecting diabetes at different cutoff points.

RESULTS

The area under the ROC curve was 0.86 using fasting plasma glucose ≥ 7.0 mmol/L as the gold standard. An A1C cutoff point of 6.26% had sensitivity of 80% and specificity of 74%, whereas an A1C cutoff point of 6.50% (recommended by the American Diabetes Association - ADA) had sensitivity of 73% and specificity of 89%.

CONCLUSIONS

A1C is a reliable alternative to fasting plasma glucose in detecting diabetes in this sample of Haitian-Americans. A cutoff point of 6.26% was the optimum value to detect type 2 diabetes.

Relationship of ethnicity and CD4 Count with glucose metabolism among HIV patients on Highly-Active Antiretroviral Therapy (HAART)

BACKGROUND

HIV patients on HAART are prone to metabolic abnormalities, including insulin resistance, lipodystrophy and diabetes. This study purports to investigate the relationship of ethnicity and CD4+ T cell count attained after stable highly-active antiretroviral treatment (HAART) with glucose metabolism in hyperrtriglyceridemic HIV patients without a history of diabetes.

METHODS

Demographic, anthropometric, clinical, endocrinologic, energy expenditure and metabolic measures were obtained in 199 multiethnic, healthy but hypertriglyceridemic HIV-infected patients [46% Hispanic, 17% African-American, 37% Non-Hispanic White (NHW)] on stable HAART without a history of diabetes. The relationship of glucose and insulin responses to ethnicity, CD4 strata (low (<300/cc) or moderate-to-high (≥ 300/cc)), and their interaction was determined.

RESULTS

African-Americans had significantly greater impairment of glucose tolerance (P < 0.05) and HbA1c levels (P < .001) than either Hispanics or NHWs. In multivariate models, after adjusting for confounders (age, sex, HIV/HAART duration, smoking, obesity, glucose, insulin and lipids), African-Americans and Hispanics had significantly higher HbA1c and 2-hour glucose levels than NHW's. Demonstrating a significant interaction between ethnicity and CD4 count (P = 0.023), African Americans with CD4 <300/cc and Hispanics with CD4 ≥300/cc had the most impaired glucose response following oral glucose challenge.

CONCLUSIONS

Among hypertriglyceridemic HIV patients on HAART, African-Americans and Hispanics are at increased risk of developing diabetes. Ethnicity also interacts with CD4+ T cell count attained on stable HAART to affect post-challenge glycemic response.

Type 2 diabetes in East Asians: similarities and differences with populations in Europe and the United States

There is an epidemic of diabetes in Asia. Type 2 diabetes develops in East Asian patients at a lower mean body mass index (BMI) compared with those of European descent. At any given BMI, East Asians have a greater amount of body fat and a tendency to visceral adiposity. In Asian patients, diabetes develops at a younger age and is characterized by early β cell dysfunction in the setting of insulin resistance, with many requiring early insulin treatment. The increasing proportion of young-onset and childhood type 2 diabetes is posing a particular threat, with these patients being at increased risk of developing diabetic complications. East Asian patients with type 2 diabetes have a higher risk of developing renal complications than Europeans and, with regard to cardiovascular complications, a predisposition for developing strokes. In addition to cardiovascular-renal disease, cancer is emerging as the other main cause of mortality. While more research is needed to explain these interethnic differences, urgent and concerted actions are needed to raise awareness, facilitate early diagnosis, and encourage preventive strategies to combat these growing disease burdens.

HbA1c for screening and diagnosis of diabetes mellitus

HbA1c has become the gold standard for monitoring glycemic control in patients with diabetes mellitus. The use of this test has been expanded to diagnose and screen for diabetes mellitus with the endorsement of influential diabetes societies and the World Health Organization. The literature on the use of HbA1c for the diagnosis and screening of diabetes mellitus was critically examined. There is substantial recent literature on this topic with strong advocates for the use of HbA1c to diagnose and screen for diabetes and equally strong detractors for its use. Advocates of the use of HbA1c cite challenges in respect of patient compliance and the analysis of glucose and inconsistency of diagnosis with glucose-based diabetes diagnosis with the elimination or reduction in these challenges in HbA1c-based diagnosis. Detractors of its use cite increased cost, concerns about the availability of HbA1c testing, and the influence of demographic and clinical factors on HbA1c results that make the use of a single-threshold values questionable for different ethnic and age groups. Despite the recommendation of many international diabetes societies that HbA1c be used for screening and diagnosis of diabetes mellitus, there is a wide divergence of opinion on this use.

Improved outcomes in diabetes care for rural African Americans

PURPOSE

Rural low-income African American patients with diabetes have traditionally poorer clinical outcomes and limited access to state-of-the-art diabetes care. We determined the effectiveness of a redesigned primary care model on patients' glycemic, blood pressure, and lipid level control.

METHODS

In 3 purposively selected, rural, fee-for-service, primary care practices, African American patients with type 2 diabetes received point-of-care education, coaching, and medication intensification from a diabetes care management team made up of a nurse, pharmacist, and dietitian. In 5 randomly selected control practices matched for practice and patient characteristics, African American patients received usual care. Using univariate and multivariate adjusted models, we evaluated the effects of the intervention on intermediate (median 18 months) and long-term (median 36 months) changes in glycated hemoglobin (hemoglobin A1c) levels, blood pressure, and lipid levels, as well as the proportion of patients meeting target values.

RESULTS

Among 727 randomly selected rural African American diabetic patients (368 intervention, 359 control), intervention patients had a significantly greater reduction in mean hemoglobin A1c levels at intermediate (-0.5 % vs -0.2%; P <.05) and long-term (-0.5% vs -0.10%; P <.005) follow-up in univariate and multivariate models. The proportion of patients achieving a hemoglobin A1c level of less than 7.5% (68% vs 59%, P <.01) and/or a systolic blood pressure of less than 140 mm Hg (69% vs 57%, P <.01) was also significantly greater in intervention practices in multivariate models.

CONCLUSION

Redesigning care strategies in rural fee-for-service primary care practices for African American patients with established diabetes results in significantly improved glycemic control relative to usual care.

Elevated rates of diabetes in Pacific Islanders and Asian subgroups: The Diabetes Study of Northern California (DISTANCE)

OBJECTIVE

We estimated the prevalence and incidence of diabetes among specific subgroups of Asians and Pacific Islanders (APIs) in a multiethnic U.S. population with uniform access to care.

RESEARCH DESIGN AND METHODS

This prospective cohort analysis included 2,123,548 adult members of Kaiser Permanente Northern California, including 1,704,363 with known race/ethnicity (white, 56.9%; Latino, 14.9%; African American, 8.0%; Filipino, 4.9%; Chinese, 4.0%; multiracial, 2.8%; Japanese, 0.9%; Native American, 0.6%; Pacific Islander, 0.5%; South Asian, 0.4%; and Southeast Asian, Korean, and Vietnamese, 0.1% each). We calculated age-standardized (to the 2010 U.S. population) and sex-adjusted diabetes prevalence at baseline and incidence (during the 2010 calendar year). Poisson models were used to estimate relative risks.

RESULTS

There were 210,632 subjects with prevalent diabetes as of 1 January 2010 and 15,357 incident cases of diabetes identified during 2010. The crude diabetes prevalence was 9.9% and the incidence was 8.0 cases per 1,000 person-years and, after standardizing by age and sex to the 2010 U.S. Census, 8.9% and 7.7 cases per 1,000 person-years. There was considerable variation among the seven largest API subgroups. Pacific Islanders, South Asians, and Filipinos had the highest prevalence (18.3, 15.9, and 16.1%, respectively) and the highest incidence (19.9, 17.2, and 14.7 cases per 1,000 person-years, respectively) of diabetes among all racial/ethnic groups, including minorities traditionally considered high risk (e.g., African Americans, Latinos, and Native Americans).

CONCLUSIONS

High rates of diabetes among Pacific Islanders, South Asians, and Filipinos are obscured by much lower rates among the large population of Chinese and several smaller Asian subgroups.

Optimal hemoglobin A1C Cutoff Value for Diagnosing type 2 diabetes mellitus in Korean adults

Commonly used tests for the diagnosis of diabetes include measurements of fasting plasma glucose levels and the oral glucose tolerance test (OGTT). Recently, a hemoglobin A1C (A1C) level of 6.5% has been included as a criterion for diabetes diagnosis by the American Diabetes Association. We aimed to determine appropriate A1C cutoff values for identifying patients with diabetes or prediabetes, including impaired glucose tolerance and impaired fasting glucose among Korean adults and to determine whether these cutoffs vary according to age. We recruited 4616 adults without a history of diabetes from 10 university hospitals. A 75-g OGTT and A1C sampling were performed in all examinees. Pointwise area under the receiver operating characteristic curve was used to evaluate the diagnostic accuracy of the A1C cutoff. An A1C threshold of 6.1% proved to be the optimal limit for diagnosing diabetes, with 63.8% sensitivity and 88.1% specificity. The cutoff value increased with age (5.9% in 18-39 years, 6.2% in 40-64 years, and 6.4% in older than 65 years) and were similar for men and women. An A1C cutoff of 5.7% had reasonable sensitivity (48.6%) and specificity (65.7%) for the identification of prediabetes. Further prospective studies should be carried out to determine whether the application of age-specific diagnostic criteria is appropriate.

The long and winding road to optimal HbA1c measurement

The importance of hemoglobin A1c (HbA1c) as an indicator of mean glycemia and risks for complications in patients with diabetes mellitus was established by the results of long-term clinical trials, most notably the Diabetes Control and Complications Trial (DCCT) and United Kingdom Prospective Diabetes Study (UKPDS), published in 1993 and 1998 respectively. However, clinical application of recommended HbA1c targets that were based on these studies was difficult due to lack of comparability of HbA1c results among assay methods and laboratories. Thus, the National Glycohemoglobin Standardization Program (NGSP) was initiated in 1996 with the goal of standardizing HbA1c results to those of the DCCT/UKPDS. HbA1c standardization efforts have been highly successful; however, a number of issues have emerged on the "long and winding road" to better HbA1c, including the development of a higher-order HbA1c reference method by the International Federation of Clinical Chemistry (IFCC), recommendations to use HbA1c to diagnose as well as monitor diabetes, and point-of-care (POC) HbA1c testing. Here, we review the past, present and future of HbA1c standardization and describe the current status of HbA1c testing, including limitations that healthcare providers need to be aware of when interpreting HbA1c results.

The metabolic deterioration that antedates diabetes: personal trajectories of HbA(1c) and fasting glucose as early indicators and possible triggers for intervention

HbA(1c) testing has become an accepted means of diagnosing diabetes as an alternative to blood glucose levels. However, population-based norms of glucose and of HbA(1c) levels do not enable the detection of diabetes at an early enough stage to thwart complications. Personal trajectories of glucose levels show steep increases a number of years prior to diabetes diagnosis. Here, we hypothesize that a comparable time-dependent deviation in an individual's HbA(1c) level may be an early manifestation of disease that should prompt lifestyle modifications. We predict that analysis of personal trajectories of glucose and of HbA(1c) will promote earlier intervention and a greater reduction in disease complications than current standards, which are based on population-based norms.

Genetics of obesity and type 2 diabetes in African Americans

Obesity and type 2 diabetes are highly prevalent and lead to significant morbidity and mortality. In the United States, the impact of these conditions may be worse on historically underserved minorities, particularly African Americans. Genetic ancestry and differences in physiology are unlikely to be the sole or primary determinants of these disparities. In addition, research in this area has the ethically problematic possibility of conflating race with biology. Despite these important considerations and the challenges of conducting this work, population-based approaches for investigating the etiology of obesity and T2D may yield useful information about the pathophysiology of disease, and have implications that extend to all affected individuals. The purpose of this paper is to describe what is understood about the genetic variation that underlies obesity and T2D in African Americans and other individuals of more recent African descent and to highlight several examples that illustrate how ensuring adequate minority representation in genetic research improves its quality. For a variety of reasons a number of unique insights have been possible as a result of these efforts.

Pathobiology of Prediabetes in a Biracial Cohort (POP-ABC) study: baseline characteristics of enrolled subjects

BACKGROUND

The Pathobiology of Prediabetes in a Biracial Cohort (POP-ABC) study is a prospective evaluation of the natural history impaired glucose regulation.

DESIGN AND METHODS

The eligibility requirements include age 18-65 yr, history of type 2 diabetes in one or both parents, normal fasting plasma glucose (FPG) or normal glucose tolerance, and African-American or Caucasian status. Participants underwent assessments (including dietary and exercise behavior, clinical examination, glucose tolerance, insulin sensitivity, β-cell function, body composition, energy expenditure) during 2.25-5.5 yr of quarterly follow-up. The primary outcome is the occurrence of prediabetes. Baseline data are presented for the 376 enrolled participants. The cohort was also compared with National Health and Nutrition Examination Survey 2007/2008 participants meeting the age and glycemic criteria for the POP-ABC study.

RESULTS

The POP-ABC cohort [mean (±SD) age was 44.2 ± 10.6 yr] was 57.7% African-Americans, 42.3% Caucasians, and 70.7% females; 86% had one parent with diabetes and 14% had both parents affected. Although greater than 70% of the cohort were employed and 75% had more than 13 yr of education, more African-Americans reported incomes less than $20,000 and fewer reported incomes more than $75,000 compared with Caucasians. Compared with Caucasians, African-Americans had a higher body mass index (31.3 ± 7.8 vs. 28.8 ± 7.8 kg/m(2), P = 0.001), a lower FPG (90.0 ± 7.72 vs. 92.2 ± 7.60 mg/dl, P = 0.008), higher glycosylated hemoglobin, lower triglycerides, and similar blood pressure, and homeostasis model assessment of insulin resistance, homeostasis model assessment of β-cell function, high-density lipoprotein, and low-density lipoprotein cholesterol levels. Compared with a cross-section of U.S. subjects (National Health and Nutrition Examination Survey 2007/2008) with normal FPG and normal glucose tolerance, participants in the POP-ABC study had similar lipid profile but were more educated and had higher body mass index, glycosylated hemoglobin, and blood pressure.

CONCLUSIONS

The POP-ABC study has successfully enrolled healthy African-American and Caucasian adults with parental type 2 diabetes mellitus. The study will generate novel data on incidence rates and predictors of prediabetes, and clarify the role of race/ethnicity on early dysglycemia.

Glycated haemoglobin and the risk of cardiovascular disease, diabetes and all-cause mortality in the Copenhagen City Heart Study

OBJECTIVE

Individuals with diabetes mellitus (DM) have a considerably elevated risk of developing serious health problems including cardiovascular disease (CVD). Long-term elevated levels of blood glucose in nondiabetic individuals may also be associated with increased risk of CVD. The aim of this study was to investigate the relationships between glycated haemoglobin A(1c) (HbA(1c) ) and CVD, DM and all-cause mortality.

SUBJECTS AND DESIGN

The Copenhagen City Heart Study is a prospective study of individuals from the Danish general population. The cohort was followed for 10 years via national registers with respect to incident CVD, DM and all-cause mortality. Follow-up was 100% complete.

RESULTS

A total of 5127 subjects were included, of whom 597 had DM. In the nondiabetic population, HbA(1c) was significantly associated with incident CVD events in both univariate [hazard ratio (HR) 1.38, 95% CI 1.11-1.71] and multivariate analyses (HR 1.31, 95% CI 1.05-1.64). In the nondiabetic population, increased levels of HbA(1c) were correlated with developing DM. There was a threefold increase in risk of incident DM per unit increase in HbA(1c) with a univariate HR of 3.83 (95% CI 1.96-7.51). This relationship was essentially unchanged after multivariate adjustments (HR 4.19, 95% CI 2.01-8.71). Furthermore, we found that net reclassification improvement for diagnosed DM and CVD was significantly improved with the addition of HbA(1c) in the analyses. Although not statistically significant, we found a strong trend towards an association between HbA(1c) and all-cause mortality (HR 1.21, 95% CI 0.99-1.47). We did not find the same associations amongst the population with DM.

CONCLUSION

In the Danish general population, HbA(1c) was strongly associated with CVD in individuals without DM.

Applicability of a combination of hemoglobin A(1c) and fasting plasma glucose in population-based prediabetes screening

BACKGROUND

The purpose of this study is to determine: (i) the concordance between a combination of hemoglobin A(1c) (Hb(A1c)) and fasting plasma glucose (FPG) (Hb(A1c) + FPG) and a combination of FPG and 2-h plasma glucose (2hPG) (FPG + 2hPG); and (ii) whether substituting FPG + 2hPG with Hb(A1c) + FPG can enhance the detection of prediabetes in diabetes-free non-Hispanic Whites, non-Hispanic Blacks, and Mexican-Americans adults.

METHODS

Data (n = 1376) from the 2007 to 2008 U.S. National Health and Nutrition Examination Surveys were used for this investigation. Prediabetes cut points were determined using 5.7-6.4%, 100-125, and 140-199 mg/dL for Hb(A1c), FPG, and 2hPG, respectively. Concordances between Hb(A1c) and FPG, Hb(A1c) and 2hPG, Hb(A1c) + FPG and FPG + 2hPG in screening for undiagnosed prediabetes were determined using sensitivity, specificity, and positive and negative likelihood ratios.

RESULTS

The overall concordance between Hb(A1c) + FPG and FPG + 2hPG in screening for prediabetes was high, as indicated by a sensitivity of 92.4% (95% CI = 90.5-94.5) and specificity of 84.1% (81.2-87.0). The application of Hb(A1c) + FPG was associated with a higher prevalence of prediabetes compared to FPG + 2hPG. Compared with FPG + 2hPG, screening with Hb(A1c) + FPG was associated with 3.2%, 24.3%, and 4.2% relative increases in the identification of prediabetes in nondiabetic non-Hispanic Whites, non-Hispanic Blacks and Mexican-Americans, respectively.

CONCLUSIONS

The enhanced prevalence of prediabetes using Hb(A1c) + FPG compared with FPG + 2hPG calls for the need to redefine at a more basic and practical level how to apply Hb(A1c) in screening for prediabetes. A redefined Hb(A1c) that incorporates FPG, age, race/ethnicity, and body mass index may be a better way to use Hb(A1c) in population-based and clinical settings.

HbA(1c) diagnostic categories and β-cell function relative to insulin sensitivity in overweight/obese adolescents

OBJECTIVE

The recommended HbA(1c) diagnostic categories remain controversial and their utility in doubt in pediatrics. We hypothesized that alterations in the pathophysiologic mechanisms of type 2 diabetes may be evident in the American Diabetes Association recommended at-risk/prediabetes category (HbA(1c) 5.7 to <6.5%).

RESEARCH DESIGN AND METHODS

We compared in vivo hepatic and peripheral insulin sensitivity by [6,6-(2)H(2)] glucose and a 3-h hyperinsulinemic-euglycemic clamp and β-cell function by a 2-h hyperglycemic clamp (∼225 mg/dL) in overweight/obese (BMI ≥85th percentile) adolescents with prediabetes (HbA(1c) 5.7 to <6.5%) (n = 160) to those with normal HbA(1c) (<5.7%) (n = 44). β-Cell function was expressed relative to insulin sensitivity (i.e., the disposition index = insulin sensitivity × first-phase insulin).

RESULTS

In the prediabetes versus normal HbA(1c) category, fasting glucose, insulin, and oral glucose tolerance test (OGTT) area under the curve for glucose and insulin were significantly higher; hepatic and peripheral insulin sensitivity were lower; and β-cell function relative to insulin sensitivity was lower (366 ± 48 vs. 524 ± 25 mg/kg/min; P = 0.005). A total of 27% of youth in the normal HbA(1c) category and 41% in the prediabetes HbA(1c) category had dysglycemia (impaired fasting glucose and/or impaired glucose tolerance) by a 2-h OGTT.

CONCLUSIONS

Overweight/obese adolescents with HbA(1c) in the at-risk/prediabetes category demonstrate impaired β-cell function relative to insulin sensitivity, a metabolic marker for heightened risk of type 2 diabetes. Thus, HbA(1c) may be a suitable screening tool in large-scale epidemiological observational and/or interventional studies examining the progression or reversal of type 2 diabetes risk.

Use of HbA1c in the diagnosis of diabetes mellitus in the UK. The implementation of World Health Organization guidance 2011

The WHO was very clear that an HbA(1c) of 48 mmol/mol (6.5%) and above is diagnostic of diabetes. They were less clear regarding results that fell below 48 mmol/mol. The WHO recognize that individuals with HbA(1c) values below the cut-off point may still have diabetes, but give no guidance on how to investigate further. It is important that these individuals, who may be at increased risk of developing diabetes, are monitored correctly; a recommended scheme is given in Fig. 2; following these recommendations will ensure at-risk people are not overlooked and will be monitored closely. Even although it is not recommended to combine HbA(1c) with glucose measurement for diagnosis, the WHO did not discount the value of a fasting glucose and an oral glucose tolerance test to diagnose diabetes in selected individuals; it is the responsibility of the investigating doctor to choose how best to diagnose on an individual basis. This new method of diagnosing diabetes will identify a different cohort as having diabetes than is currently being diagnosed; but the process of investigation that does not require a fasting sample makes investigation easier, allowing more people to be investigated.

Diabetes control among Hispanics in the action to control cardiovascular risk in diabetes trial

BACKGROUND

Hispanics in the United States represent diverse racial, ethnic, and socioeconomic groups, and manifest heterogeneous cardiovascular risks including diabetes. It is not known if there are residual differences in the control of diabetes among Hispanic groups given uniform access to diabetes care.

OBJECTIVE

To evaluate glucose control differences among Mexicans, Puerto Ricans, and Dominicans receiving substantial diabetes care and support in the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial.

DESIGN

Secondary analysis of data from a randomized trial comparing two treatment strategies: intensive, targeting glycated hemoglobin below 6.0 %, and standard, targeting glycated hemoglobin between 7.0 % and 7.9 %.

PARTICIPANTS

Seven hundred and sixteen Hispanic and 6066 non-Hispanic white participants were recruited from 77 clinical sites across the United States and Canada. There were 243 Mexicans, 199 Puerto Ricans, and 150 Dominicans; and 135 of these Hispanic groups were born in the United States.

MAIN MEASURE

Glycated hemoglobin

RESULTS

Compared to Puerto Ricans, Mexicans were more likely (HR=1.38, CI:0.90-2.10) and Dominicans as likely (HR=1.01, CI:0.66-1.54) to achieve glycated hemoglobin goal in the intensive arm. Participants born in the United States achieved glycated hemoglobin goal at a higher rate than those born elsewhere (HR=1.57, CI:0.99-2.51 in the intensive arm, HR=1.51, CI:0.95-2.43 in the standard arm). These differences were not statistically significant. In the intensive arm, Puerto Ricans (OR=0.47, CI:0.31-0.71), and Dominicans (OR=0.41, CI:0.26-0.66) were less likely than non-Hispanic whites to achieve glycated hemoglobin goal, whereas the difference between non-Hispanic whites and Mexicans was not statistically significant, (OR=0.66, CI:0.43-1.02).

CONCLUSIONS

Hispanic groups, given access to comprehensive diabetes care, differed from each other non-significantly and had a variable divergence from non-Hispanic whites in achieving intensive glycated hemoglobin goal. These differences, if confirmed, could be due to such factors as variable acculturation and functional health literacy levels that were not measured in the ACCORD trial, but should be further explored in future studies.

Accuracy of glycated haemoglobin in screening for pre-diabetes in Asian Indians--a community survey: the Chandigarh Urban Diabetes Study (CUDS)

AIM

To compare American Diabetes Association and International Expert Committee recommended cut-off values of HbA(1c) for detecting the presence of pre-diabetes against plasma glucose values obtained from oral glucose tolerance tests in Asian Indians.

METHODS

A cross-sectional randomly sampled population survey involving 2368 adults, aged ≥ 20 years. HbA(1c) was measured on a Bio-Rad 10 system in 1972 subjects.

RESULTS

Of the 1972 subjects studied, 329 were detected to have pre-diabetes based on isolated impaired fasting glucose in 125 subjects (6.3%), isolated impaired glucose tolerance in 141 subjects (7.1%) and the presence of both in 63 subjects (3.2%). The HbA(1c) cut-off of 34 mmol/mol (5.7%), as recommended by the American Diabetes Association for detecting the presence of pre-diabetes, showed sensitivity of 62%, specificity 77%, with a positive predictive value of 34.7%, a negative predictive value of 89.5% and accuracy of 67.8%; whereas the HbA(1c) cut-off recommended by the International Expert Committee of 42 mmol/mol (6%) had a sensitivity of 36%, specificity of 90%, positive predictive value of 42.7%, negative predictive of 85.4% and an accuracy of 77%. However, both these HbA(1c) cut-offs underdiagnosed the presence of pre-diabetes in 38 and 64% of these subjects, respectively.

CONCLUSIONS

The American Diabetes Association and the International Expert Committee recommended HbA(1c) cut-off values and oral glucose tolerance tests identify different pre-diabetes cohorts. Long-term prospective studies are required to define the usefulness of one over the other.

Glycated hemoglobin in diagnosis of diabetes mellitus and pre-diabetes; validation by oral glucose tolerance test. The Tromsø OGTT Study

BACKGROUND

Glycated hemoglobin (HbA(1c)) 6.5% has recently been recommended by the World Health Organization (WHO) and the American Diabetes Association (ADA) as an alternative diagnostic criterion for diabetes mellitus (DM).

AIM

To evaluate HbA(1c) as an alternative to oral glucose tolerance test (OGTT) for diagnosis of DM and pre-diabetes and to find the optimal HbA(1c) cut-off points for DM and pre-diabetes in our population.

SUBJECTS AND METHODS

The subjects were recruited from the Tromsø Study, performed for the 6th time in 2007-2008 with 12,984 participants. All subjects with HbA(1c) in the range 5.8-6.9% and a random sample of subjects with levels 5.3-5.7% were invited to an OGTT.

RESULTS

Among 3476 subjects who completed the OGTT, 199 were diagnosed with DM. The best sensitivity (69.8%) and specificity (81.8%) were found at HbA(1c) 6.2%. For HbA(1c) 6.5% we found a sensitivity of 34.7% and specificity 97.1%. The best cut-off points for impaired fasting glucose (no.=314) and impaired glucose tolerance (no.=404) were found at HbA(1c) 5.9% and 6.0%, respectively. Pre-diabetes detected only by OGTT was associated with worse metabolic characteristics than pre-diabetes detected only by HbA(1c).

CONCLUSIONS

The optimum HbA(1c) cutoff point for DM in our population was lower than that proposed by WHO and ADA. To establish more precisely the HbA(1c) levels predictive of micro- and macro-vascular complications, long-term prospective studies are needed. Population- specific optimum cut-off points may be necessary.

Ethnic disparity in hemoglobin A1c levels among normoglycemic offspring of parents with type 2 diabetes mellitus

OBJECTIVE

To investigate the racial/ethnic disparities in hemoglobin A1c levels among nondiabetic persons with similar parental history of type 2 diabetes mellitus.

METHODS

We studied a community-based sample of adult offspring of parents with type 2 diabetes mellitus. Measurements included anthropometry, hematology assessments, serial fasting plasma glucose, oral glucose tolerance testing, plasma insulin, hemoglobin A1c, insulin sensitivity, and β-cell function, using a homeostasis model assessment.

RESULTS

The study included 302 participants (135 white, 167 black). Compared with white participants, black participants had lower fasting plasma glucose levels (91.9 ± 0.51 mg/dL vs 93.6 ± 0.50 mg/dL, P = .015), lower area under the curve of plasma glucose during oral glucose tolerance testing (P = <.001), higher body mass index (31.1 ± 0.61 kg/m² vs 28.5 ± 0.57 kg/m², P = <.001), and similar insulin sensitivity and β-cell function. Hemoglobin A1c was higher in black participants than in white participants (5.68 ± 0.033% vs 5.45 ± 0.028%, P<.001). The absolute black-white difference in hemoglobin A1c level of approximately 0.22% persisted after adjusting for age, hemoglobin, hematocrit, body mass index, waist circumference, fasting plasma glucose, glucose area under the curve, and other covariates.

CONCLUSIONS

Among healthy offspring of parents with type 2 diabetes mellitus in this study, African American participants had higher hemoglobin A1c levels than white participants after adjusting for age, adiposity, blood glucose, and known variables. Thus, plasma glucose level is more valid than hemoglobin A1c for diagnosing prediabetes or diabetes in black persons.

Association of acculturation and country of origin with self-reported hypertension and diabetes in a heterogeneous Hispanic population

Background

Hispanics are the fasting growing population in the U.S. and disproportionately suffer from chronic diseases such as hypertension and diabetes. Little is known about the complex interplay between acculturation and chronic disease prevalence in the growing and increasingly diverse Hispanic population. We explored the association between diabetes and hypertension prevalence among distinct U.S. Hispanic subgroups by country of origin and by degree of acculturation.

Methods

We examined the adult participants in the 2001, 2003, 2005, and 2007 California Health Interview Survey (CHIS). Using weighted logistic regression stratified by nativity, we measured the association between country of origin and self-reported hypertension and diabetes adjusting for participants’ demographics, insurance status, socio-economic status and degree of acculturation measured by citizenship, English language proficiency and the number of years of residence in the U.S.

Results

There were 33,633 self-identified Hispanics (foreign-born: 19,988; U.S.-born: 13,645). After multivariable adjustment, we found significant heterogeneity in self-reported hypertension and diabetes prevalence among Hispanic subgroups. Increasing years of U.S. residence was associated with increased disease prevalence. Among all foreign-born subgroups, only Mexicans reported lower odds of hypertension after adjustment for socioeconomic and acculturation factors. Both U.S.-born and foreign-born Mexicans had higher rates of diabetes as compared to non-Hispanic whites.

Conclusions

We found significant heterogeneity among Hispanics in self-reported rates of hypertension and diabetes by acculturation and country of origin. Our findings highlight the importance of disaggregation of Hispanics by country of origin and acculturation factors whenever possible.

Should the hemoglobin A1c diagnostic cutoff differ between blacks and whites? A cross-sectional study

BACKGROUND

Hemoglobin A1c (HbA1c) levels are known to be consistently higher in black persons than in white persons at any given glycemic level. Whether the optimal diagnostic threshold of HbA1c should differ between blacks and whites is unclear.

OBJECTIVE

To compare the relationships between HbA1c level and the prevalence of retinopathy in black and white U.S. adults.

DESIGN

Cross-sectional study.

SETTING

A nationally representative sample of the National Health and Nutrition Examination Survey from 2005 through 2008.

PATIENTS

2804 white persons and 1008 black persons aged 40 years or older in the United States.

MEASUREMENTS

Prevalence of retinopathy. Logistic regression models and restricted cubic spline models were constructed separately for white and black populations to test the HbA1c levels at which risk for retinopathy begins to increase.

RESULTS

After adjustment for age, sex, hypertension, body mass index, family history of diabetes, and use of antidiabetes medications or insulin, the lowest HbA1c category for which the prevalence of retinopathy was significantly higher than the reference category (<5.5%) was 6.0% to 6.4% for white persons (risk difference, 4.8% [95% CI, 0.5% to 9.1%]) and 5.5% to 5.9% for black persons (risk difference, 5.3% [CI, 1.0% to 9.5%]). The restricted cubic spline models indicated that the risk for retinopathy increased at lower HbA1c levels in black persons than in white persons.

LIMITATION

The cross-sectional design of the study precluded examining the effect of the duration at each HbA1c level.

CONCLUSION

The prevalence of retinopathy begins to increase at a lower HbA1c level in black Americans than in white Americans. The findings do not support increasing the diagnostic threshold of HbA1c in black persons.

PRIMARY FUNDING SOURCE

None.

Independent effect of ethnicity on glycemia in South Asians and white Europeans

OBJECTIVE

HbA(1c) levels are higher in most ethnic groups compared with white Europeans (WEs) independent of glycemic control. This comparison has not been performed between South Asians (SAs) and WEs. We analyzed the independent effect of ethnicity on HbA(1c) and fasting and 2-h plasma glucose (FPG and 2 hrPG, respectively) between these groups.

RESEARCH DESIGN AND METHODS

Analysis of the ADDITION-Leicester study, in which 4,688 WEs and 1,352 SAs underwent oral glucose tolerance testing, HbA(1c), and other risk factor measurements.

RESULTS

Significant associations with HbA(1c) included ethnicity, FPG, 2 hrPG, and homeostasis model assessment of β-cell function (P < 0.001); age and sex (P < 0.01); and fasting insulin and potassium (P < 0.05). After adjusting for these and other risk factors, SAs demonstrated higher HbA(1c) (6.22 and 6.02%, mean difference 0.20%, 0.10-0.30, P < 0.001), FPG (5.15 and 5.30 mmol/L, mean difference 0.15 mmol/L, 0.09-0.21, P < 0.001), and 2 hrPG (5.82 and 6.57 mmol/L, mean difference 0.75 mmol/L, 0.59-0.92, P < 0.001) compared with WEs, respectively.

CONCLUSIONS

HbA(1c), FPG, and 2 hrPG levels were higher in SAs independent of factors affecting glycemic control.

Choosing targets for glycaemia, blood pressure and low-density lipoprotein cholesterol in elderly individuals with diabetes mellitus

Diabetes mellitus in the 'elderly' poses unique management challenges that contribute to conflicting priorities. Individualized management requires taking into account each patient's medical history, functional ability, home care situation, life expectancy and his/her health beliefs; individuals value trade-offs (e.g. quantity versus quality of life, and side effects as well as risks versus long-term benefits) differently. Moreover, this decision making relies on imperfect evidence. Target goals for three intermediate outcomes - glycaemic control (glycosylated haemoglobin [HbA(1c)]), blood pressure control and lipid control (low-density lipoprotein cholesterol [LDL-C]) - help keep management on track. Of these, glycaemic control is usually the most complex. Glycaemic control alleviates symptoms of hyperglycaemia and can improve micro- and macrovascular outcomes. Tight glycaemic control (HbA(1c) <7%) clearly improves microvascular outcomes. However, hypoglycaemia and polypharmacy are the main drawbacks of tight control. Factors that influence the benefits and drawbacks include age, longevity and co-morbidities, including the geriatric 'syndromes' of frailty and falls. We favour the explicit risk-stratified approach of the Department of Veterans Affairs/Department of Defense (VA/DoD) guidelines, which set HbA(1c) target ranges based on physiological age or the presence/severity of major co-morbidities and microvascular complications. There are clear benefits of blood pressure and cholesterol control (primarily reduction of macrovascular events, but also microvascular events), and their overall cost effectiveness exceeds that of glycaemic control. Issues with treatment for hypertension include potential side effects of drugs, a potential increased risk of falls and risks of polypharmacy. Nevertheless, the evidence for a blood pressure target of <140/80 mmHg is reasonably strong if it can be achieved safely. In general, we recommend use of an HMG-CoA reductase inhibitor (statin) and an LDL-C target of <100 mg/dL, especially if an individual cannot tolerate a moderate dose of a statin.