Tests of glycemia in diabetes

Point-of-care testing for Hb A1c in the management of diabetes: a systematic review and metaanalysis

BACKGROUND

The measurement of hemoglobin A(1c) (Hb A(1c)) is employed in monitoring of patients with diabetes. Use of point-of-care testing (POCT) for Hb A(1c) results at the time of the patient consultation potentially provides an opportunity for greater interaction between patient and caregiver, and more effective care.

OBJECTIVE

To perform a systematic review of current trials to determine whether POCT for Hb A(1c), compared with conventional laboratory testing, improves outcomes for patients with diabetes.

METHODS

Searches were undertaken on 4 electronic databases and bibliographies from, and hand searches of, relevant journal papers. Only randomized controlled trials were included. The primary outcome measures were change in Hb A(1c) and treatment intensification. Metaanalyses were performed on the data obtained.

RESULTS

Seven trials were found. There was a nonsignificant reduction of 0.09% (95% CI -0.21 to 0.02) in the Hb A(1c) in the POCT compared to the standard group. Although data were collected on the change in proportion of patients reaching a target Hb A(1c) of <7.0%, treatment intensification and heterogeneity in the populations studied and how measures were reported precluded pooling of data and metaanalysis. Positive patient satisfaction was also reported in the studies, as well as limited assessments of costs.

CONCLUSIONS

There is an absence of evidence in clinical trial data to date for the effectiveness of POCT for Hb A(1c) in the management of diabetes. In future studies attention to trial design is needed to ensure appropriate selection and stratification of patients, collection of outcome measures, and action taken upon Hb A(1c) results when produced.

Hemoglobin A1c as a predictor of incident diabetes

OBJECTIVE

Several studies have suggested that HbA(1c) levels may predict incident diabetes. With new recommendations for use of HbA(1c) in diagnosing diabetes, many patients with HbA(1c) results below the diagnostic threshold will be identified. Clinicians will need to categorize risk for a subsequent diabetic diagnosis in such patients. The objective of this study was to determine the ability of HbA(1c) to predict the incidence of a diabetic diagnosis.

RESEARCH DESIGN AND METHODS

We performed a historical cohort study using electronic medical record data from two Department of Veterans Affairs Medical Centers. Patients (n = 12,589) were identified with a baseline HbA(1c) <6.5% between January 2000 and December 2001 and without a diagnosis of diabetes. Patients (12,375) had at least one subsequent follow-up visit. These patients were tracked for 8 years for a subsequent diagnosis of diabetes.

RESULTS

During an average follow-up of 4.4 years, 3,329 (26.9%) developed diabetes. HbA(1c) ≥ 5.0% carried a significant risk for developing diabetes during follow-up. When compared with the reference group (HbA(1c) <4.5%), HbA(1c) increments of 0.5% between 5.0 and 6.4% had adjusted odds ratios of 1.70 (5.0-5.4%), 4.87 (5.5-5.9%), and 16.06 (6.0-6.4%) (P < 0.0001). Estimates of hazard ratios similarly showed significant increases for HbA(1c) ≥ 5.0%. A risk model for incident diabetes within 5 years was developed and validated using HbA(1c), age, BMI, and systolic blood pressure.

CONCLUSIONS

The incidence of diabetes progressively and significantly increased among patients with an HbA(1c) ≥ 5.0%, with substantially expanded risk for those with HbA(1c) 6.0-6.4%.

Effects of a structured self-monitoring of blood glucose method on patient self-management behavior and metabolic outcomes in type 2 diabetes mellitus

BACKGROUND

The purpose of this study was to evaluate the effect of structured self-monitoring of blood glucose (SMBG) on patient self-management behavior and metabolic outcomes in patients with type 2 diabetes mellitus (T2DM).

METHODS

From January to June 2009, 30 patients with basic diabetes education were followed for a period of 90 days. To provide assessment of glycemic control and frequency of dysglycemia, patients, underwent 3 consecutive days of seven-point SMBG during each month for 3 consecutive months, using the ACCU-CHEK 360° View tool. Glucose profiles of the first and third month were used for comparison.

RESULTS

Hemoglobin A1c (HbA1c) improved significantly during the 90-day period in all patients [confidence interval (CI) 95%, 0.32-1.64%, p < .05] and those with poor metabolic control (group B; CI 95%, 0.86-2.64%, p < .05). Mean blood glucose (MBG) values decreased significantly in group B (CI 95%, 0.56-24.78 mg/dl, p < .05) and all cases (CI 95%, 1.61-19.73 mg/dl, p < .05). Meanwhile, there was an average decrease of 15.7 mg/dl in fasting blood sugar (FBS) levels in the whole subjects. Mean postprandial blood glucose levels (MPP) decreased by 19.3 and 11.3 mg/dl in group B and in all cases, respectively. However, there were no significant changes in HbA1c, MBG, FBS, and MPP in people with good metabolic control.

CONCLUSION

A structured SMBG program improves HbA1c, FBS, MPP, and MBG in people with poorly controlled diabetes. This improvement shows the importance of patient self-management behavior on metabolic outcomes in T2DM.

Cost effectiveness and cost utility of the noncoding blood glucose meter CONTOUR TS

AIMS

This study assessed the cost efficacy and cost utility of the automatic blood glucose meter CONTOUR(®) TS from the public payer (National Health Fund [NHF]) and payer (patient and NHF) perspectives over a 26-year analysis horizon.

METHODS

Clinical effectiveness data were obtained from prior clinical studies of automatic versus manually coded blood glucose meters. Cost data were obtained from the NHF. The probability of procedure use related to diabetic complications was obtained from four medical centers in Poland. The incremental cost-effectiveness ratio related to 1 life year gained and the incremental cost-utility ratio related to 1 quality-adjusted life year gained were calculated.

RESULTS

Assuming co-funding from public funds, introduction of the CONTOUR(®) TS is associated with savings of Polish zloty (PLN) 31,846.19 (€ 8916.93) and PLN 113,018.19 (€ 31,645.09) per life year gained from the payer and public payer perspectives, respectively. Cost utility analyses showed that the CONTOUR(®) TS is associated with savings of PLN 40,465.59 (€ 11,330.37) and PLN 11,434.82 (€ 3201.75) per quality-adjusted life year gained from the payer and the public payer perspectives, respectively.

CONCLUSION

The CONTOUR(®) TS appears superior to manually coded meters available in Poland both from the payer and the public payer perspectives and may represent an improved strategy for glycemic control.

Measurement of hemoglobin A1c from filter papers for population-based studies

BACKGROUND

Stability and transport challenges make hemoglobin (Hb) A(1c) measurement from EDTA whole blood (WB) inconvenient and costly for large-scale population studies. This study investigated Hb A(1c) measurement from WB blotted on filter paper (FP) in a Level I National Glycohemoglobin Standardization Program (NGSP)-accredited laboratory.

METHODS

Three Bio-Rad Variant™ II HPLC instruments and WB and FP specimens were used. Precision, accuracy, linearity, and readable total area of the 6.5-min (β-thalassemia method) Variant II HbA(2)/HbA(1c) Dual Program were assessed. Hb A(1c) stability was measured using in-house FP QC samples. The INTERHEART (a study of the effect of potentially modifiable risk factors associated with myocardial infarction in 52 countries) and CURE (Clopidogrel in Unstable Angina to Prevent Recurrent Events) studies provided chromatographs for morphometric analyses and interoperator variability experiments. Statistical analyses were performed to assess long-term sample stability, WB vs FP agreement, and significance of Hb A(1c) peak integration.

RESULTS

Intra- and interassay CVs were ≤2.00%. Total area counts between 0.8 and 5.5 × 10(6) μV/s produced accurate Hb A(1c) results. The regression equation for agreement between WB(x) and FP(y) was as follows: y = 0.933x + 0.4 (n = 85). FP QC samples stored at -70 °C and tested over approximately 3 years yielded CVs of 1.72%-2.73% and regression equations with slopes of -1.08 × 10(-4) to 7.81 × 10(-4). The CURE study, with better preanalytical preparation, achieved a 97% reportable rate, and the reportable rate of the INTERHEART study was 85%.

CONCLUSIONS

The FP collection method described provided accurate, robust, and reproducible measurement of Hb A(1c) using the Bio-Rad Variant II HPLC autoanalyzer when FP specimens were prepared according to standardized protocols, and analyses were performed in an NGSP-certified laboratory, supporting the use of FP collection cards in large multinational studies.

Estimating plasma glucose from interstitial glucose: the issue of calibration algorithms in commercial continuous glucose monitoring devices

Evaluation of metabolic control of diabetic people has been classically performed measuring glucose concentrations in blood samples. Due to the potential improvement it offers in diabetes care, continuous glucose monitoring (CGM) in the subcutaneous tissue is gaining popularity among both patients and physicians. However, devices for CGM measure glucose concentration in compartments other than blood, usually the interstitial space. This means that CGM need calibration against blood glucose values, and the accuracy of the estimation of blood glucose will also depend on the calibration algorithm. The complexity of the relationship between glucose dynamics in blood and the interstitial space, contrasts with the simplistic approach of calibration algorithms currently implemented in commercial CGM devices, translating in suboptimal accuracy. The present review will analyze the issue of calibration algorithms for CGM, focusing exclusively on the commercially available glucose sensors.

Echocardiographic findings of congenital cardiopathies among fetuses of diabetic pregnant women and their relationship with plasma fructosamine levels

OBJECTIVE

To study the occurrence of congenital cardiopathies at echocardiography (CCE) in fetuses whose mothers had preexisting diabetes mellitus (PGDM) and to study the potential of using fructosamine level as a late marker (beyond the first trimester) for CCE.

METHODS

A register study covering 91 pregnant women that underwent routine fetal echocardiography ordered due to PGDM. The first dosage of plasma fructosamine found in 65 medical records was analyzed during prenatal care (20.4 ± 8.0 weeks of gestation). The presence or absence of structural or functional CCE was associated with fructosamine levels by logistic regression. We assessed the effect modification odds ratio by maternal age and insulin usage.

RESULTS

Thirty-four fetuses (52.3% of 65 fetuses) presented CCE. Twenty of them had functional CCE and 14 presented structural CCE. The mean maternal plasma fructosamine level was higher among pregnant women whose fetuses presented CCE than in those whose fetuses did not (2.86 ± 0.73 mmol/l, 2.22 ± 0.54 mmol/l, respectively, p < 0.0001). Crude OR for CCE and abnormal plasma fructosamine (>2.68 mmol/l) was 9.6 (2.8-33.7, 95% CI, p < 0.0001). Adjusted OR by maternal age and insulin usage was 10.9 (2.7-45.2, 95% CI p < 0.0001).

CONCLUSIONS

An abnormal plasma fructosamine level increases the chances of CCE occurring among referral pregnant women with PGDM.

The effect of iron and erythropoietin treatment on the A1C of patients with diabetes and chronic kidney disease

OBJECTIVE

To examine the effect of intravenous iron and erythropoietin-stimulating agents (ESAs) on glycemic control and A1C of patients with diabetes and chronic kidney disease (CKD).

RESEARCH DESIGN AND METHODS

This was a prospective study of patients with type 2 diabetes and CKD stage IIIB or IV undergoing intravenous iron (group A) and/or ESA (group B). Full blood profiles were determined over the study period. Glycemic control was monitored using A1C, seven-point daily glucose three times weekly, and continuous glucose monitoring (CGM).

RESULTS

There were 15 patients in both group A and group B. Mean A1C (95% CI) values fell in both groups (7.40% [6.60-8.19] to 6.96% [6.27-7.25], P<0.01, with intravenous iron and 7.31% [6.42-8.54] to 6.63% [6.03-7.36], P=0.013, ESA). There was no change in mean blood glucose in group A (9.55 mmol/l [8.20-10.90] vs. 9.71 mmol/l [8.29-11.13], P=0.07) and in group B (8.72 mmol/l [7.31-10.12] vs. 8.78 mmol/l [7.47-9.99], P=0.61) over the study period. Hemoglobin and hematocrit values significantly increased following both treatments. There was no linear relationship found between the change in A1C values and the rise of hemoglobin following either treatment.

CONCLUSIONS

Both iron and ESA cause a significant fall in A1C values without a change to glycemic control in patients with diabetes and CKD. At the present time, regular capillary glucose measurements and the concurrent use of CGM remain the best alternative measurements of glycemic control in this patient group.

Impact of A1C screening criterion on the diagnosis of pre-diabetes among U.S. adults

OBJECTIVE

New clinical practice recommendations include A1C as an alternative to fasting glucose as a diagnostic test for identifying pre-diabetes. The impact of these new recommendations on the diagnosis of pre-diabetes is unknown.

RESEARCH DESIGN AND METHODS

Data from the National Health and Nutrition Examination Survey 1999-2006 (n = 7,029) were analyzed to determine the percentage and number of U.S. adults without diabetes classified as having pre-diabetes by the elevated A1C (5.7-6.4%) and by the impaired fasting glucose (IFG) (fasting glucose 100-125 mg/dl) criterion separately. Test characteristics (sensitivity, specificity, and positive and negative predictive values) using IFG as the reference standard were calculated.

RESULTS

The prevalence of pre-diabetes among U.S. adults was 12.6% by the A1C criterion and 28.2% by the fasting glucose criterion. Only 7.7% of U.S. adults, reflecting 61 and 27% of those with pre-diabetes by A1C and fasting glucose, respectively, had pre-diabetes according to both definitions. A1C used alone would reclassify 37.6 million Americans with IFG to not having pre-diabetes and 8.9 million without IFG to having pre-diabetes (46.5 million reclassified). Using IFG as the reference standard, pre-diabetes by the A1C criterion has 27% sensitivity, 93% specificity, 61% positive predictive value, and 77% negative predictive value.

CONCLUSIONS

Using A1C as the pre-diabetes criterion would reclassify the pre-diabetes diagnosis of nearly 50 million Americans. It is imperative that clinicians and health systems understand the differences and similarities in using A1C or IFG in diagnosis of pre-diabetes.

Novel biomarkers in cardiovascular disease: update 2010

The rapid evaluation of patients presenting with symptoms suggestive of an acute coronary syndrome is of great clinical relevance. Biomarkers have become increasingly important in this setting to supplement electrocardiographic findings and patient history because one or both can be misleading. Today, cardiac troponin is still the only marker used routinely in this setting due to its myocardial tissue specificity and sensitivity, as well as its established usefulness for therapeutic decision making. However, even current generation troponin assays have certain limitations such as insufficient sensitivity for diagnosing unstable angina. Novel high-sensitivity assays for cardiac troponin have the potential to overcome these limitations. Further studies are needed to answer some critical questions regarding the best cutoffs for diagnosis and risk assessment and the optimal work-up for rule-out of acute myocardial infarction. Other nonmyocardial tissue-specific markers might help in this setting. Myeloperoxidase, copeptin, and growth differentiation factor 15 reflect different aspects of the development of atherosclerosis or acute ischemia. Each has demonstrated impact in risk stratification of acute coronary syndromes. Limited data also show that copeptin may, when used together with cardiac troponin, improve the sensitivity for diagnosing acute myocardial infarction, and growth differentiation factor 15 may help in selection of patients that benefit from invasive therapy. Further evaluation is needed before these markers can be adopted routinely in clinical practice.

Clinical analysis of elderly patients with elderly-onset type 2 diabetes mellitus in China: assessment of appropriate therapy

Patients with elderly-onset diabetes have specific characteristics. This study was designed to investigate these characteristics and to evaluate methods for appropriate control of glycaemia and cardiovascular risk factors in elderly-onset diabetes patients. A total of 155 elderly patients with type 2 diabetes mellitus were divided into those diagnosed at >or= 65 years of age (elderly-onset group, 75 patients) and those diagnosed at < 60 years of age (usual-onset group, 80 patients). Differences in clinical variables, diabetic complications, diagnosed comorbidities and the use of medications were analysed. Mean glycosylated haemoglobin, fasting plasma glucose and fasting insulin levels were significantly lower in the elderly-onset group than in the usual-onset group. The usual-onset group showed significantly greater homeostasis model assessment insulin resistance than the elderly-onset group. Microvascular complications and insulin use were significantly more common in the usual-onset group. In conclusion, insulin resistance was less severe in elderly-onset diabetes than in usual-onset diabetes. As hyperglycaemia was relatively mild or moderate, oral hypoglycaemic agents might be effective for elderly-onset diabetes.

Do patient autonomy preferences matter? Linking patient-centered care to patient-physician relationships and health outcomes

As health care systems seek to provide patient-centered care as a cornerstone of quality, the link between patient-centeredness and patient outcomes is a concern. Past research reveals inconsistent findings regarding the impact of patient-centeredness on patient outcomes, and few studies have investigated the factors that moderate this relationship. Most studies have used self-rated outcomes on a cross-sectional basis, even though most patient care is inherently longitudinal. The current study extends past research by examining the theoretical and empirical relationships between patients' perceptions of autonomy support and autonomy preferences with regard to their health outcomes. We hypothesized that autonomy preferences moderate the positive relationships between perceived autonomy support and patient-physician relationships, and on self-rated and objective health outcomes such that the relationships are more positive when patient autonomy preferences are high. Data were collected 3 times over a one-year period from a sample of 614 patients with type 2 diabetes in Taiwan. The results revealed strong support for the hypothesized relationships between perceived autonomy support and patient trust, satisfaction, and mental health-related quality of life (HRQoL) after adjusting for baseline scores; however, the direct link between autonomy support and patients' glycemic control was not significant. Specifically, patients with high decisional preference experienced a greater increase in subsequent trust and satisfaction than patients with low decisional preference. Further, patients with high information preference had a higher level of satisfaction over time than patients with low information preference. In addition, it was found that perceived autonomy support improved both physical and mental HRQoL but only if combined with high levels of information preference. This study provides evidence of a contingency perspective of the relationship between patient autonomy support and outcomes. By recognizing the uniqueness of each patient's autonomy preferences, healthcare practitioners can increase the efficiency of patient-centered care and improve patient outcomes.

Use of sensors in the treatment and follow-up of patients with diabetes mellitus

Glucose control is the cornerstone of Diabetes Mellitus (DM) treatment. Although self-regulation using capillary glycemia (SRCG) still remains the best procedure in clinical practice, continuous glucose monitoring systems (CGM) offer the possibility of continuous and dynamic assessment of interstitial glucose concentration. CGM systems have the potential to improve glycemic control while decreasing the incidence of hypoglycemia but the efficiency, compared with SRCG, is still debated. CGM systems have the greatest potential value in patients with hypoglycemic unawareness and in controlling daily fluctuations in blood glucose. The implementation of continuous monitoring in the standard clinical setting has not yet been established but a new generation of open and close loop subcutaneous insulin infusion devices are emerging making insulin treatment and glycemic control more reliable.

Standardization of HbA1c: good or bad?

The development of a true reference measurement system by the International Federation for Clinical Chemistry (IFCC) for the first time allows reporting of true HbA(1c) results, standardized to an absolute value, worldwide. Regression equations between the IFCC assay and current harmonization assays, including the Diabetes Control and Complications Trial (DCCT) assay, are linear, tight, and stable over time. National and international setting of targets, audit and benchmarking of services will be easier than before, as will translation of research into clinical practice. Nevertheless, the main disadvantage of the IFCC assay is that the numbers and units reported (mmol/mol) are very different from the DCCT value (percentage). An extensive education program for patients and health-care professionals is, therefore, needed to prevent confusion and consequent deterioration in glycemic control. Furthermore, the IFCC system does not overcome difficulties inherent in the measurement and interpretation of HbA(1c), such as in the presence of abnormal turnover of red blood cells and hemoglobinopathies.

Glycated haemoglobin A1c for diagnosing diabetes in Chinese population: cross sectional epidemiological survey

OBJECTIVES

To evaluate haemoglobin A1c (HbA(1c)) in diagnosing diabetes and identify the optimal HbA(1c) threshold to be used in Chinese adults.

DESIGN

Multistage stratified cross sectional epidemiological survey.

SETTING

Shanghai, China, 2007-8.

PARTICIPANTS

4886 Chinese adults over 20 years of age with no history of diabetes.

MAIN OUTCOME MEASURES

Performance of HbA(1c) at increasing thresholds for diagnosing diabetes.

RESULTS

The area under the receiver operating characteristics curve for detecting undiagnosed diabetes was 0.856 (95% confidence interval 0.828 to 0.883) for HbA(1c) alone and 0.920 (0.900 to 0.941) for fasting plasma glucose alone. Very high specificity (96.1%, 95% confidence interval 95.5% to 96.7%) was achieved at an HbA(1c) threshold of 6.3% (2 SD above the normal mean). Moreover, the corresponding sensitivity was 62.8% (57.1% to 68.3%), which was equivalent to that of a fasting plasma glucose threshold of 7.0 mmol/l (57.5%, 51.7% to 63.1%) in detecting undiagnosed diabetes. In participants at high risk of diabetes, the HbA(1c) threshold of 6.3% showed significantly higher sensitivity (66.9%, 61.0% to 72.5%) than both fasting plasma glucose >or=7.0 mmol/l (54.4%, 48.3% to 60.4%) and HbA(1c) >or=6.5% (53.7%, 47.6% to 59.7%) (P<0.01).

CONCLUSIONS

An HbA(1c) threshold of 6.3% was highly specific for detecting undiagnosed diabetes in Chinese adults and had sensitivity similar to that of using a fasting plasma glucose threshold of 7.0 mmol/l. This optimal HbA(1c) threshold may be suitable as a diagnostic criterion for diabetes in Chinese adults when fasting plasma glucose and oral glucose tolerance tests are not available.

Treatment of periodontal disease for glycaemic control in people with diabetes

BACKGROUND

Glycaemic control is a key issue in the care of people with diabetes mellitus (DM). Some studies have suggested a bidirectional relationship between glycaemic control and periodontal disease.

OBJECTIVES

To investigate the relationship between periodontal therapy and glycaemic control in people with diabetes and to identify the appropriate future strategy for this question.

SEARCH STRATEGY

A comprehensive approach was adopted employing handsearching; searching of electronic databases including the Cochrane Oral Health Group's Trials Register, CENTRAL, MEDLINE, EMBASE, CINAHL, ZETOC, ISI Web of Knowledge and LILACS; contact with appropriate non-English language healthcare professionals; authors and organisations. The final date for searching for studies was 24th March 2010.

SELECTION CRITERIA

This review studied randomised controlled trials of people with Type 1 or 2 diabetes mellitus (DM) with a diagnosis of periodontitis. Suitable interventions included mechanical periodontal therapy with or without adjunctives and oral hygiene education.

DATA COLLECTION AND ANALYSIS

The titles and abstracts of 690 papers were examined by two review authors independently. Ultimately, seven studies were included and 19 excluded after full text scrutiny. All trials were assessed for risk of bias.

MAIN RESULTS

Three studies had results pooled into a meta-analysis. The effect for the mean percentage difference in HbA1c for scaling/root planing and oral hygiene (+/- antibiotic therapy) versus no treatment/usual treatment after 3/4 months was -0.40% (95% confidence interval (CI) fixed effect -0.78% to -0.01%), representing a statistically significant reduction in HbA1c (P = 0.04) for scaling/root planing. One study was assessed as being at low risk of bias with the other two at moderate to high risk of bias. A subgroup analysis examined studies without adjunctive antibiotics -0.80% (one study: 95% CI -1.73% to 0.13%; P = 0.09), with adjunctive antibiotics in the test group -0.36% (one study: 95% CI -0.83% to 0.11%; P = 0.14), and with antibiotics in both test and control groups after 3/4 months -0.15% (one study: 95% CI -1.04% to 0.74%; P = 0.74).

AUTHORS' CONCLUSIONS

There is some evidence of improvement in metabolic control in people with diabetes, after treating periodontal disease. There are few studies available and individually these lacked the power to detect a significant effect. Most of the participants in the study had poorly controlled Type 2 DM with little data from randomised trials on the effects on people with Type 1 DM.Improving periodontal health is an important objective in itself. However, in order to understand the potential of this treatment to improve glycaemic control among people with diabetes, larger, carefully conducted and reported studies are needed.

Statistical models for the control phase of clinical monitoring

The rise in the prevalence of chronic conditions means that these are now the leading causes of death and disability worldwide, accounting for almost 60% of all deaths and 43% of the global burden of disease. Management of chronic conditions requires both effective treatment and ongoing monitoring. Although costs related to monitoring are substantial, there is relatively little evidence on its effectiveness. Monitoring is inherently different to diagnosis in its use of regularly repeated tests, and increasing frequency can result in poorer rather than better statistical properties because of multiple testing in the presence of high variability. We present here a general framework for modelling the control phase of a monitoring programme, and for the estimation of quantities of potential clinical interest such as the ratio of false to true positive tests. We show how four recent clinical studies of monitoring cardiovascular disease, hypertension, diabetes and HIV infection can be thought as special cases of this framework; as well as using this framework to clarify the choice of estimation and calculation methods available. Noticeably, in each of the presented examples over-frequent monitoring appears to be a greater problem than under-frequent monitoring. We also present recalculations of results under alternative conditions, illustrating conceptual decisions about modelling the true or observed value of a clinical measure.

Glucose biosensors: an overview of use in clinical practice

Blood glucose monitoring has been established as a valuable tool in the management of diabetes. Since maintaining normal blood glucose levels is recommended, a series of suitable glucose biosensors have been developed. During the last 50 years, glucose biosensor technology including point-of-care devices, continuous glucose monitoring systems and noninvasive glucose monitoring systems has been significantly improved. However, there continues to be several challenges related to the achievement of accurate and reliable glucose monitoring. Further technical improvements in glucose biosensors, standardization of the analytical goals for their performance, and continuously assessing and training lay users are required. This article reviews the brief history, basic principles, analytical performance, and the present status of glucose biosensors in the clinical practice.

Value of hemoglobin A1c in diagnosing diabetes mellitus within a chronic disease management system illustrated by the receiver operating characteristic curve

OBJECTIVE

To develop a receiver operating characteristic (ROC) curve of glycosylated hemoglobin (HbA1c) for diagnosing diabetes mellitus within a chronic disease management system.

METHODS

A case-control study including medical records from January 1, 1997, to December 31, 2005, was conducted at the Sioux Falls Veterans Affairs Medical Center. Medical records for the case group (patients with diabetes) were selected based on 1 of 3 criteria: International Classification of Diseases, Ninth Revision, Clinical Modification or Current Procedural Terminology codes specific for type 1 and type 2 diabetes; patients' use of medications (oral hypoglycemic agents, antidiabetes agents, or insulin); or results from random blood or plasma glucose tests (at least 2 measurements of blood glucose > or = 200 mg/dL). Records for the control group were selected based on patients having HbA1c measured, but not meeting the above diagnostic criteria for diabetes during the study period. Records for cases and controls were randomly frequency-matched, one-to-one. The control group was randomly divided into 5 sets of an equal number of records. Five sets of an equal number of cases were then randomly selected from the total number of cases. Each test data set included 1 case group and 1 control group, resulting in 5 independent data sets.

RESULTS

In total, 5040 patient records met the case definition in the diabetes registry. Records of 15 patients who were prescribed metformin only, but did not meet any other case criteria, were reviewed and excluded after determining the patients were not diabetic. The control group consisted of 5 sets of 616 records each (totaling 3080 records), and the case group consisted of 5 sets of 616 records each (totaling 3080 records). Thus, each of the 5 independent data sets of 1 case group and 1 control group contained 1232 records. The case group was predominantly composed of white men (mean age, 69 years; mean body mass index, 31 kg/m2). Demographic data were similar for control patients. The ROC curve revealed that a HbA1c > or = 6.3% (mean + 1 SD) offered the most accurate cutoff value for diagnosing type 2 diabetes mellitus, with the following statistical values: C statistic, 0.78; sensitivity, 70%; specificity, 85%; and positive likelihood ratio, 4.6 (95% confidence interval, 4.2-5.0).

CONCLUSION

A HbA1c value > or = 6.3% may be a useful benchmark for diagnosing diabetes mellitus within a chronic disease management system and may be a useful tool for monitoring high-risk populations.

The use of low-glycaemic index diets in diabetes control

The aim of diabetes management is to normalise blood glucose levels since improved blood glucose control is associated with fewer complications. Food affects blood glucose levels; however, there is no universal approach to the optimal diabetic diet and there is controversy about the usefulness of the low-glycaemic index (GI) diet. To assess the effects of low-GI diets on glycaemic control in diabetes, we conducted electronic searches of the Cochrane Library, MEDLINE, EMBASE and CINAHL. We assessed randomised controlled trials (RCT) with interventions >4 weeks that compared a low-GI diet with a higher-GI diet for type 1 or type 2 diabetes. Twelve RCT (n612) were identified. There was a significant decrease in glycated Hb (HbA1c) with low-GI diet than with the control diet, indicating improved glycaemic control (seven trials,n457, weighted mean difference (WMD) − 0·4 % HbA1c, 95 % CI − 0·7, − 0·20,P = 0·001). In four studies reporting the results for glycaemic control as fructosamine, three of which were 6 weeks or less in duration, pooled data showed a decrease in fructosamine (WMD − 0·23 mmol/l, 95 % CI − 0·47, 0·00,P = 0·05),n141, with low-GI diet than with high-GI diet. Glycosylated albumin levels decreased significantly with low-GI diet, but not with high-GI diet, in one study that reported this outcome. Lowering the GI of the diet may contribute to improved glycaemic control in diabetes.

[Performance characteristics of glycated albumin and its clinical usefulness in diabetic patients on hemodialysis]

BACKGROUND

The HbA1c has been considered to underestimate glucose level in diabetic patients on hemodialysis, therefore, glycated albumin (GA) was recently introduced to assess the glycemic control for those cases. We evaluated the performance of GA assay kit of Lucica GA-L (Asahi Kasei Pharma Co., Japan) and compare it with HbA1c for estimating glucose levels.

METHODS

Tests for precision, linearity and interference were performed and reference interval was determined. Thirty eight of non-hemodialysis and seventy of hemodialysis patients were recruited, whose glucose levels of three-, two- and one-month prior to this study were available for calculating weighted means of glucose (WMGs). The correlation coefficients and the slopes of regression equation between WMG and HbA1c or GA were compared between two groups. Multiple linear regression analyses were used to determine significant predictor for HbA1c and GA.

RESULTS

Total CV was 2.2% at concentration of 13.7% and 2.8% at 24.6%. The dilution curve between 15.7% and 62.1% was linear. Reference intervals were 10.0% to 16.5% for male and 11.4% to 17.6% for female. The correlation coefficients between WMG and GA were 0.682-0.713 in hemodialysis and 0.640-0.677 in non-hemodialysis. Those between WMG and HbA1c were 0.568-0.625 in hemodialysis and 0.735-0.783 in non-hemodialysis. The slopes of regression equation between GA and WMG in hemodialysis were 0.080-0.090 and 0.130-0.147 in non-hemodialysis. Those between HbA1c and WMG in hemodialysis were 0.012-0.014 and 0.029-0.032 in non-hemodialysis. GA was not influenced by hemodialysis status while HbA1c was.

CONCLUSIONS

The claimed performance characteristic of Lucica GA-L were verified. WMG were better reflected by GA rather than HbA1c in patients on hemodialysis.

Hemoglobin A(1c) and fructosamine for assessing glycemic control in diabetic patients with CKD stages 3 and 4

BACKGROUND

Hemoglobin A(1c) (HbA(1c)) and fructosamine can be used to monitor glycemic control in diabetic patients with normal kidney function, but their validity in patients with chronic kidney disease (CKD) has not been evaluated. In this study, we evaluated the correlation and accuracy of these 2 measures of glycemic control in type 2 diabetic patients with CKD stages 3-4.

STUDY DESIGN

Diagnostic test study.

SETTING & PARTICIPANTS

Type 2 diabetic patients with normal (n = 30) and abnormal kidney function (n = 30) were recruited in Taipei Veterans General Hospital, Taiwan.

INDEX TESTS

HbA(1c) and fructosamine.

REFERENCE TEST

Self-monitoring of blood glucose levels.

MEASUREMENTS

Blood glucose measurements consisted of 6 preprandial, 6 postprandial, and 2 bedtime assessments in a week with a cycle of 4-week intervals for 12 weeks.

RESULTS

Correlation coefficients between HbA(1c) level or fructosamine-albumin ratio and mean blood glucose levels were 0.836 and 0.645 in participants with normal kidney function and 0.813 and 0.649 in participants with CKD stages 3-4, respectively. In patients with CKD stages 3-4, mean blood glucose levels in weeks 1-12 were 21.9 mg/dL (95% CI, 11.6-32.5) higher than estimated average glucose (eAG) levels calculated from HbA(1c) levels in participants with normal kidney function. In patients with CKD stages 3-4, mean blood glucose levels in weeks 10-12 were 15.5 mg/dL (95% CI, 5.2-30.5) higher than eAG levels calculated from fructosamine levels in participants with normal kidney function, but without statistical significance when eAG calculated from fructosamine level was corrected for serum albumin level (difference of 5.6 mg/dL; 95% CI, -8.6 to 19.8).

LIMITATIONS

Relatively small number of participants with limited amount of blood glucose measurement data.

CONCLUSION

Our data show that eAG calculated from HbA(1c) and fructosamine levels might underestimate mean blood glucose levels in patients with CKD stages 3-4. References ranges may need to be modified when interpreting results of measurements of glycemic control in type 2 diabetic patients with CKD.

Impact of cardiovascular outcomes on the development and approval of medications for the treatment of diabetes mellitus

All medications currently approved by the Food and Drug Administration (FDA) for the treatment of type 2 diabetes mellitus are indicated to improve glycemic control. Since 1995, FDA has used HbA1c as the primary basis for approval of these therapies because a reduction in blood glucose lessens the symptoms of hyperglycemia and lowering of HbA1c has been shown to reduce the risk for some of the chronic complications of diabetes. Despite evidence of clinical benefit with therapies that reduce HbA1c, concerns have been raised that some diabetes medications may increase cardiovascular risk in a patient population that is already vulnerable to cardiovascular disease. Therefore, FDA convened a public advisory committee meeting to discuss the role of cardiovascular assessment in the pre-approval and post-approval settings for medications developed for the treatment of type 2 diabetes. After considering the advisory panel's recommendations and other data, FDA published a guidance document requesting evidence showing that new treatments for type 2 diabetes do not result in an unacceptable increase in cardiovascular risk. This review article begins by summarizing the events leading up to publication of this guidance. Subsequent sections discuss the guidance itself as well as general considerations for implementing the new cardiovascular recommendations. The new approach to developing medications for the treatment of type 2 diabetes will lead to evaluation in patients more representative of those who will use these therapies, if approved, and will help healthcare providers make informed decisions when choosing a medication within the growing treatment armamentarium for type 2 diabetes.

Antidepressant pharmacotherapy in adults with type 2 diabetes: rates and predictors of initial response

OBJECTIVE Initial treatment with antidepressant medication is insufficiently effective in some patients with type 2 diabetes, and factors predicting treatment outcome are poorly understood. RESEARCH DESIGN AND METHODS Aggregate data from two published trials were analyzed to determine the rates and predictors of response to antidepressant pharmacotherapy in adults with type 2 diabetes using conventional markers of initial treatment outcome (improvement, response, partial remission, and remission). Three hundred eighty-seven patients who received up to 16 weeks of open-label, acute-phase treatment using bupropion (n = 93) or sertraline (n = 294) were studied. Logistic regression was used to identify predictors of poor treatment outcome. Candidate predictors included age, race, sex, initial Beck Depression Inventory (iBDI) score, treatment received (sertraline or bupropion), family history of depression, extant diabetes complications (eDC), and A1C level. RESULTS Of 387 patients initiated on treatment, 330 (85.3%) met criteria for improvement, 232 (59.9%) for response, 207 (53.5%) for partial remission, and 179 (46.3%) for full remission. Significant independent predictors of poor outcome included eDC (for no improvement); sertraline treatment, eDC, and younger age (for nonresponse); sertraline treatment, eDC, and higher iBDI (for failure to partially remit); and younger age and higher iBDI (for failure to fully remit). Higher pain scores predicted three of the four markers of poor outcome in the subset with pain data. CONCLUSIONS In patients with type 2 diabetes, poor initial response to antidepressant medication is predicted by multiple factors. Auxiliary treatment of pain and impairment may be required to achieve better outcomes.

Non-enzymatic glycation of proteins: from diabetes to cancer

Incubation of proteins with glucose leads to their non-enzymatic glycation and formation of Amadori products known as an early glycation product. Oxidative cleavage of Amadori products is considered as a major route to advanced glycation endproducts (AGEs) formation in vivo. Nonenzymatic glycation of proteins or Maillard reaction is increased in diabetes mellitus due to hyperglycemia and leads to several complications such as blindness, heart disease, nerve damage and kidney failure. Accumulation of the early and advanced glycation products in plasma and tissues of diabetic patients and causes production of autoantibodies against corresponding products. The advanced glycation products are also associated with other diseases like cancer. This review summarizes current knowledge of these stage specific glycated products as common and early diagnostic biomarkers for the associated diseases and the complications with the aim of a novel therapeutic target for the diseases.

Glycated albumin levels are higher relative to glycated haemoglobin levels in gastrectomized subjects

Background

In gastrectomized subjects, oral glucose tolerance test often shows marked hyperglycaemia (oxyhyperglycaemia) after glucose loading. Because serum glycated albumin (GA) has been shown to better reflect postprandial and maximum plasma glucose levels, we investigated whether or not the clinical significance of serum GA and glycated haemoglobin (HbA1C) in non-diabetic gastrectomized subjects differs.

Methods

During health examinations, 62 non-diabetic subjects with a history of gastrectomy and 87 non-diabetic control subjects were selected in the present study. Body mass index (BMI) in the gastrectomy group was significantly lower than in the control group.

Results

Fasting plasma glucose levels were significantly lower in the gastrectomized subjects than in the control subjects. Although both HbA1C and serum GA were significantly higher in the gastrectomized subjects, there was a significant difference in GA/HbA1C ratio between the gastrectomized subjects and the control subjects. BMI-adjusted serum GA, based on our previous finding of inverse influence of BMI on serum GA, was also significantly higher in the gastrectomized subjects than in the controls.

Conclusions

Serum GA is higher relative to HbA1C in gastrectomized subjects. This suggests that serum GA may be a better marker than HbA1C for glycaemic excursion in these subjects.

Depressive symptomatology mediates the effect of socioeconomic disadvantage on HbA(1c) among rural African Americans with type 2 diabetes

OBJECTIVE

Rural African Americans with diabetes mellitus type 2 (T2D) represent a disadvantaged and understudied group who experience difficulties with maintaining glycemic control. Although mounting evidence has linked socioeconomic disadvantage to chronic disease morbidity, few studies have examined the mediating mechanisms that account for this effect. We hypothesized that rural African Americans' financial distress, community disadvantage, and educational attainment would predict glycemic control, indirectly, via effects on depressive symptoms.

METHODS

Predictions were tested using data from 192 rural African American adults with T2D and data from community support persons the participants nominated. Participants completed an in-home interview and provided a blood sample at a local laboratory. Levels of glycosylated hemoglobin (HbA(1c)) constituted the criterion variable.

RESULTS

Structural equation modeling analyses confirmed our hypotheses: financial distress, community disadvantage, and educational attainment demonstrated significant indirect effects on HbA(1c) via their influence on depressive symptoms.

CONCLUSIONS

The findings underscore the importance of targeting mental health in interventions to support glycemic control as well as tailoring interventions for individuals in difficult socioeconomic circumstances.

Association of glucose measures with total and coronary heart disease mortality: does the effect change with time? The Rancho Bernardo Study

AIMS

To compare the associations of three glucose measures with coronary heart disease (CHD) and total mortality and to examine how these associations changed over time.

METHODS

Prospective study of 1774 adults (median age 68 years, 56% female). Fasting plasma glucose (FPG), 2h post-challenge glucose (2hPG), and glycohemoglobin (GHb) were obtained in 1984-1987. Mortality data was obtained for all participants. Multivariable Cox models examined the association of baseline glucose measures with mortality during sequential periods of follow-up (0-6, 7-12, and 13-18 years), adjusting for age, sex, blood pressure, LDL-cholesterol, smoking, exercise, and aspirin use.

RESULTS

854 (48%) participants died during follow-up. In adjusted models, only GHb was associated with total mortality over the entire 18 years (p=0.007). In analyses of mortality in successive six year time intervals, the association of GHb and total mortality was only significant in years 0-6. For each 1% increase in GHb, the hazard ratio for death in years 0-6 was 1.14 (95% CI 1.01-1.30, p=0.04) and the hazard ratio for CHD death was 1.26 (95% CI 1.03-1.55, p=0.02). Stratification by sex and exclusion of participants with diabetes did not change our results.

CONCLUSIONS

Higher levels of GHb were associated with increased total and CHD mortality within the first six years independent of cardiac risk factors. Though further research is needed, this supports the hypothesis that early glycemic control may affect mortality outcomes.

Clinical use of fructosamine in islet transplantation

Many islet transplant recipients have medical conditions that could interfere with the accuracy of HbA1c measurements (e.g., anemia/dapsone use). Fructosamine is less prone to have clinical interferences and reflects glucose control in a shorter period of time than HbA1c. This study aimed to validate fructosamine use in islet transplant subjects and to evaluate its effectiveness as a predictor for islet graft dysfunction. Thirty-three islet transplant recipients who had concomitant fructosamine and HbA1c data available were retrospectively analyzed. HbA1c, fructosamine, mean capillary blood glucose, and islet graft function (fasting C-peptide/glucose ratio) were assessed. There was a significant and positive association between fructosamine and HbA1c (p < 0.0001). Both variables were also positively associated with mean overall and fasting capillary glucose. Neither fructosamine nor HbA1c was shown by ROC analysis to significantly discriminate between periods with and without subsequent graft dysfunction. HbA1c >6% was predictive of this outcome 1 month in advance (OR 2.95, p = 0.003). However, although significantly associated with graft dysfunction, use of this cutoff as a predictor of dysfunction has poor sensitivity (50%) and specificity (77.6%). Fructosamine above the normal range (>270 mumol/L Quest Diagnostics) was also predictive of ensuing dysfunction (OR 2.47, p = 0.03); however, it had similarly poor sensitivity (62%) and specificity (64%). Fructosamine can be used as an alternative to HbA1c for glycemic assessment in islet transplant recipients in situations with HbA1c assay interference. Neither HbA1c nor fructosamine are good predictors of islet graft dysfunction.

Relationship of hemoglobin A1C and mortality in heart failure patients with diabetes

OBJECTIVES

This study was designed to examine the relationship between glycosylated hemoglobin (HbA1C) and adverse outcomes in diabetic patients with established heart failure (HF).

BACKGROUND

Despite the common coexistence of diabetes and HF, previous studies examining the association between HbA1C and outcomes in this population have been limited and have reported discrepant results.

METHODS

We assessed the association between increasing quintiles (Q1 to Q5) of HbA1C and risk of death or risk of HF hospitalization by conducting a retrospective study in a national cohort of 5,815 veterans with HF and diabetes treated in ambulatory clinics at Veterans Affairs medical centers.

RESULTS

At 2 years of follow-up, death occurred in 25% of patients in Q1 (HbA1C < or =6.4%), 23% in Q2 (6.4% < HbA1c < or =7.1%), 17.7% in Q3 (7.1% < HbA1c < or =7.8%), 22.5% in Q4 (7.8% < HbA1c < or =9.0%), and 23.2% in Q5 (HbA1c >9.0%). After adjustment for potential confounders, the middle quintile (Q3) had reduced mortality when compared with the lowest quintile (risk-adjusted hazard ratio: 0.73, 95% confidence interval: 0.61 to 0.88, p = 0.001). Hospitalization rates for HF at 2 years increased with increasing quintiles of HbA1C (Q1: 13.3%, Q2: 13.1%, Q3: 15.5%, Q4: 16.4%, and Q5: 18.2%), but this association was not statistically significant when adjusted for potential confounders.

CONCLUSIONS

The association between mortality and HbA1C in diabetic patients with HF appears U-shaped, with the lowest risk of death in those patients with modest glucose control (7.1% < HbA1C < or =7.8%). Future prospective studies are necessary to define optimal treatment goals in these patients.

Predicting steady-state HbA1c responses to sitagliptin in patients with type 2 diabetes mellitus

AIMS

To develop predictive formulas using short-term changes in glycaemic parameters [haemoglobin A1c (HbA1c) and fasting plasma glucose (FPG)] with sitagliptin, a highly selective dipeptidyl peptidase-4 inhibitor, to assess longer term steady-state changes in HbA1c.

METHODS

Results from two, 12-week, double-blind studies of sitagliptin in Japanese patients with type 2 diabetes mellitus receiving once-daily sitagliptin 100 mg were used to construct linear models to develop predictive formulas based on study 1 (S1) and to validate them using study 2 (S2). HbA1c and FPG were the primary and the key secondary end-point for both studies and were both used to develop predictive formulas.

RESULTS

The predictive formulas using HbA1c+/-FPG results (slope of change) from week 0 to week 4 in S1 showed high correlations between fitted and observed week 12 HbA1c: for HbA1c alone R2=0.76, for HbA1c+FPG R2=0.89. When using the sitagliptin 100 mg group of S2 data set to assess the validity of the predictive formulas, high correlations for HbA1c alone (R2=0.76) and for HbA1c+FPG (R2=0.77) were also observed. Data using a lower dose (25 mg once daily) of sitagliptin also demonstrated similar results.

CONCLUSIONS

The early responses (over 4 weeks) in HbA1c and FPG with sitagliptin can be used to accurately predict later responses (at week 12) in HbA1c in Japanese patients with type 2 diabetes mellitus. Additional studies applying this approach to other agents with diverse mechanisms are important.

Perspectives for practice: translating estimated average glucose (eAG) to promote diabetes self-management capacity

PURPOSE

The purpose of this article is to facilitate translation of the Consensus Statement to practice for diabetes educators and other professionals who contribute to the care of individuals with diabetes.

METHODS

The 2007 Consensus Statement from the American Diabetes Association (ADA), European Association for the Study of Diabetes (EASD), International Federation of Clinical Chemistry and Laboratory Medicine (IFCC), and International Diabetes Federation (IDF) called for the standardization of glycated hemoglobin measurement in reporting and use of average glucose values in clinical practice.

RESULTS

Conversion of glycated hemoglobin percentage to average blood glucose was anchored historically in early laboratory techniques linked to disease outcomes rather than to definitive laboratory standardization. Recently, the A1C-Derived Average Glucose (ADAG) study demonstrated that A1C values can be accurately expressed as estimated average glucose (eAG) and endorsed eAG as the best way to standardize the expression of laboratory values of glycated hemoglobin.

CONCLUSIONS

Adoption of the 2007 Consensus Statement will influence clinical practice and decision making and subsequently influence self-management for individuals with diabetes.

Circulating biomarkers of glycemia in diabetes management and implications for personalized medicine

Personalized medicine represents a new model in how the medical community approaches disease management. Rather than managing those with a particular diagnosis according to an established guideline, the personalized medicine model seeks to identify unique characteristics within each patient that can serve as a basis for disease characterization and specialized treatment. This article reviews several circulating biomarkers of glycemia that are used in the medical management of diabetes, to include hemoglobin A1c, fructosamine, and 1,5-anhydroglucitol. Within the discussion, specific attention is paid to areas in which biomarker results do not correlate with anticipated results based on actual mean glycemia. Variability between actual and anticipated results of the various biomarker tests represents opportunities to identify previously undefined subcategories of diabetes and groups of patients that fit into these subcategories. Finally, research areas are proposed for these subcategories that would further promote the field of personalized medicine in diabetes.

Tuberculosis in poorly controlled type 2 diabetes: altered cytokine expression in peripheral white blood cells

BACKGROUND

Although the biological basis for the increased susceptibility of diabetic patients to tuberculosis remains unclear, the world is undergoing a type 2 diabetes pandemic. We hypothesize that chronic hyperglycemia leads to immunocompromise that facilitates progression to active tuberculosis. To assess this possibility, we determined whether patients with tuberculosis and diabetes (particularly those with chronic hyperglycemia), compared with patients with tuberculosis who did not have diabetes, presented altered cytokine responses to a mycobacterial antigen.

METHODS

Samples of whole blood from patients with tuberculosis and diabetes and from patients with tuberculosis who did not have diabetes was stimulated in vitro with purified protein derivative from Mycobacterium tuberculosis. We then determined whether there was an association between the levels of innate and adaptive cytokines secreted in response to the antigen and diabetes status, or diabetes with chronic hyperglycemia (measured by glycosylated hemoglobin level), after controlling for possible confounders.

RESULTS

Innate and type 1 cytokine responses were significantly higher in patients with tuberculosis who had diabetes than in nondiabetic control subjects. The effect was consistently and significantly more marked in diabetic patients with chronic hyperglycemia.

CONCLUSIONS

These data provide preliminary evidence that type 2 diabetes, especially type 2 diabetes involving chronic hyperglycemia, is associated with an altered immune response to M. tuberculosis. More-detailed knowledge of the underlying mechanisms should focus on the effect of chronic hyperglycemia on the immune response to help in understanding the enhanced susceptibility of diabetic patients to tuberculosis.