The abbreviated glucose tolerance test in screening for diabetes: the Islington Diabetes Survey

Chinese herbal medicines for people with impaired glucose tolerance or impaired fasting blood glucose

BACKGROUND

Around 308 million people worldwide are estimated to have impaired glucose tolerance (IGT); 25% to 75% of these will develop diabetes within a decade of initial diagnosis. At diagnosis, half will have tissue-related damage and all have an increased risk for coronary heart disease.

OBJECTIVES

The objective of this review was to assess the effects and safety of Chinese herbal medicines for the treatment of people with impaired glucose tolerance or impaired fasting glucose (IFG).

SEARCH STRATEGY

We searched the following databases: The Cochrane Library, PubMed, EMBASE, AMED, a range of Chinese language databases, SIGLE and databases of ongoing trials.

SELECTION CRITERIA

Randomised clinical trials comparing Chinese herbal medicines with placebo, no treatment, pharmacological or non-pharmacological interventions in people with IGT or IFG were considered.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data. Trials were assessed for risk of bias against key criteria: random sequence generation, allocation concealment, blinding of participants, outcome assessors and intervention providers, incomplete outcome data, selective outcome reporting and other sources of bias.

MAIN RESULTS

This review examined 16 trials lasting four weeks to two years involving 1391 participants receiving 15 different Chinese herbal medicines in eight different comparisons. No trial reported on mortality, morbidity or costs. No serious adverse events like severe hypoglycaemia were observed. Meta-analysis of eight trials showed that those receiving Chinese herbal medicines combined with lifestyle modification were more than twice as likely to have their fasting plasma glucose levels return to normal levels (i.e. fasting plasma glucose <7.8 mmol/L and 2hr blood glucose <11.1 mmol/L) compared to lifestyle modification alone (RR 2.07; 95% confidence intervall (CI) 1.52 to 2.82). Those receiving Chinese herbs were less likely to progress to diabetes over the duration of the trial (RR 0.33; 95% CI 0.19 to 0.58). However, all trials had a considerable risk of bias and none of the specific herbal medicines comparison data was available from more than one study. Moreover, results could have been confounded by rates of natural reversion to normal glucose levels.

AUTHORS' CONCLUSIONS

The positive evidence in favour of Chinese herbal medicines for the treatment of IGT or IFG is constrained by the following factors: lack of trials that tested the same herbal medicine, lack of details on co-interventions, unclear methods of randomisation, poor reporting and other risks of bias.

Persistent impaired glucose tolerance, insulin resistance, and β-cell dysfunction were independent predictors of type 2 diabetes

BACKGROUND AND OBJECTIVE

To compare clinical profiles and risk of diabetes between subjects with transient (trIGT) and persistent (pIGT) impaired glucose tolerance in Taiwan.

STUDY DESIGN AND SETTING

In the pIGT group, IGT was diagnosed in two consecutive periods (1992-1994 and 1995-1996); in the trIGT group, the diagnosis was IGT at the baseline but normal glucose tolerance in the second period. The normal group was defined by fasting plasma glucose < 6.1 mmol/L and 2-hour post-load plasma glucose < 7.8 mmol/L in both periods. All three groups were considered eligible subjects for further follow up (1998-1999).

RESULTS

Among 298 nondiabetic subjects at baseline, there were 29 new cases of diabetes diagnosed according to 1999 WHO criteria in 1,614.3 person-years of follow-up (1.79%/year; 95% CI = 1.14-2.44%/year). Among subjects with normal, trIGT, or pIGT, the incidence rates were 0.73%/year (8/1,093.0; 95% CI = 0.22-1.24%/year), 2.57%/year (7/272.2; 95% CI = 0.67-4.47%/year), and 5.62%/year (14/249.1; 95% CI = 2.68-8.56%/year), respectively.

CONCLUSION

The group with trIGT had abnormal glucose tolerance and beta-cell dysfunction, which may represent an earlier stage than the group with pIGT in development of type 2 diabetes. Moreover, pIGT, insulin resistance, and beta-cell dysfunction played independent roles in the deterioration from IGT to diabetes.

Diabetes, insulin resistance, and the metabolic syndrome in patients with acute myocardial infarction without previously known diabetes

OBJECTIVE

Individuals with diabetes have an increased morbidity from acute myocardial infarction (AMI). Based on an oral glucose tolerance test (OGTT), 40-45% of patients with AMI have diabetes. The objective of this study was to characterize the glucometabolic profile of patients with AMI without known diabetes and to see if sustained glucometabolic perturbations are predictable during the hospital phase of the disease.

RESEARCH DESIGN AND METHODS

A total of 145 patients with AMI and no previous diagnosis of diabetes were subjected to an OGTT at hospital discharge and 3 months thereafter. Based on the OGTT after 3 months, they were defined as having normal glucose tolerance (NGT; n = 50), impaired glucose tolerance (IGT; n = 59), or diabetes (n = 36). Components of the metabolic syndrome, including insulin resistance assessed by homeostasis model assessment (HOMA-IR), were recorded.

RESULTS

Patients with AMI had no changes in insulin resistance from hospital discharge to follow-up. An OGTT and/or a single blood glucose taken 60 min (BG-60) after ingestion of 75 g glucose at hospital discharge were predictors of the outcome of the OGTT at follow-up. With a cutoff value for BG-60 of 8.6 mmol/l, 70% of the patients were correctly predicted as either belonging to the NGT group or the IGT/diabetes group after 3 months. Age, BMI, antihypertensive treatment, HbA(1c), fasting blood glucose, blood lipids, insulin, proinsulin, HOMA-IR, and plasminogen activator inhibitor 1 did not add predictive power.

CONCLUSIONS

Patients with AMI and no previous diagnosis of diabetes have no changes in insulin resistance from hospital discharge to a 3-month follow-up. An OGTT or a single BG-60 performed at hospital discharge predicts the diagnosis of IGT or diabetes 3 months thereafter.

Intra-individual variation of glucose, specific insulin and proinsulin concentrations measured by two oral glucose tolerance tests in a general Caucasian population: the Hoorn Study

We studied the intra-individual variation in plasma glucose, specific serum insulin and serum proinsulin concentrations, measured by two 75-g oral glucose tolerance tests in an age, sex, and glucose tolerance stratified random sample from a 50-74-year-old Caucasian population without a history of diabetes mellitus. The intra-individual variation was assessed by the standard deviation of the test-retest differences (SDdif). For subjects with normal (n = 246), impaired glucose tolerance (n = 198), and newly detected diabetes (n = 80) classified at the first test, the following (SDdif/median level of individual average scores) were found: fasting glucose: 0.4/5.4, 0.5/5.9 and 0.7/7.2 mmol/l; 2-h glucose: 1.3/5.6, 1.8/8.5 and 2.3/12.8 mmol/l; fasting insulin: 23/76, 32/89 and 30/116 pmol/l; 2-h insulin: 190/303, 278/553 and 304/626 pmol/l; fasting proinsulin: 4/8, 6/13 and 9/18 pmol/l; 2-h proinsulin: 19/49, 23/84 and 33/90 pmol/l, respectively. In both glucose, proinsulin and insulin concentrations the total intra-individual variation was predominantly determined by biological variation, whereas analytical variation made only a minor contribution. The SDdif can easily be interpreted, as 95% of the random test-retest differences will be less than 2.SDdif, or in terms of percentage, less than (2.SDdif/median level of individual average score) 100. Therefore, for subjects with normal glucose tolerance, 95% of the random test-retest differences will be less than 15% (fasting glucose), 46% (2-h glucose), 61% (fasting insulin), 125% (2-h insulin), 100% (fasting proinsulin) and 78% (2-h proinsulin) of the median value of the individual average scores. No substantial independent association of either age, gender or obesity with the intra-individual variation in glucose, proinsulin, or insulin concentrations was found.

Prevalence of diabetes mellitus and impaired glucose tolerance in a middle-aged Finnish population

OBJECTIVE

To describe the prevalence of previously diagnosed and undiagnosed diabetes and impaired glucose tolerance (IGT) by sex, marital status, employment, exercise behaviour, and body mass index (BMI), and to compare previously diagnosed and undiagnosed diabetic patients.

DESIGN

A survey of the total 55-year-old population living in a Finnish city on 1 October 1990. All the participants who were not on antidiabetic medication were invited for an oral glucose tolerance test (OGTT).

SETTING

Oulu, a city in northern Finland.

SUBJECTS

1,008 eligible subjects (456 men and 552 women), of whom 345 men (76%) and 435 women (79%) participated.

MAIN RESULTS

The prevalence of previously diagnosed diabetes was 6.1% in the men and 3.0% in the women and that of previously undiagnosed diabetes 4.5% of the men and 3.7% of the women. The prevalence of IGT was 28.6% in the men and 26.7% in the women. Diabetes was related to BMI, and previously undiagnosed diabetes was related to the amount of physical exercise in both sexes. One third of the undiagnosed diabetic men and half of the undiagnosed diabetic women were identified among the persons with marked obesity (BMI 30 kg/m2 or more). The group of previously diagnosed diabetic patients included a significantly greater proportion of retired people and people on sick leave than the group of undiagnosed diabetic persons.

CONCLUSIONS

Diabetes is common in middle-aged Finns. Undiagnosed diabetes was detected especially in persons with marked obesity who were not physically active.

A comparison of the relationships of the glucose tolerance test and the glycated haemoglobin assay with diabetic vascular disease in the community. The Islington Diabetes Survey

We have compared the relationships of fasting and 2 h blood-glucose during a 75 g oral glucose tolerance test, and those of an affinity chromatography assay of glycated haemoglobin, with the presence of vascular complications of diabetes mellitus in 223 subjects without known diabetes aged over 40 years selected from a community screening study population. The subjects included 15 (6.9%) with newly diagnosed diabetes and 52 (24.1%) with impaired glucose tolerance. Employing receiver operating characteristic analysis, the tests were similar in their relationship with three cases of retinopathy, 19 of microalbuminuria and six of peripheral neuropathy. The prevalence of coronary heart disease, defined as angina, myocardial infarction, or electrocardiographic changes of ischaemia, increased linearly across all four quartiles of both 2 h blood glucose and glycated haemoglobin concentration, but using logistic regression analysis, 2 h blood glucose was a better predictor of coronary heart disease than glycated haemoglobin. Receiver operating characteristic analysis also showed that 2 h blood glucose generally performed better than any of four assays of glycated haemoglobin in classifying those subjects with coronary heart disease.

Misclassification of diabetic subjects may account for the increased vascular risk of impaired glucose tolerance: the Islington Diabetes Survey

We have studied the associations of macrovascular disease and hypertension with impaired glucose tolerance in a recall sample of 223 subjects selected from a population aged greater than or equal to 40 years who had been screened for diabetes using two separate glucose tolerance tests. Blood pressure was higher in subjects with diabetes, but not in those with impaired glucose tolerance, than in normals. Coronary heart disease, based on ECG criteria and history, was more frequent both in subjects with impaired glucose tolerance (odds ratio 1.94, 95% CI 1.02-3.69) and those with diabetes (odds ratio 3.88, 95% CI 1.33-11.97) than in normals, but the excess in the impaired glucose tolerance group was reduced, and was no longer significant, when adjusted for other variables (odds ratio 1.29, 95% CI 0.62-2.66). Peripheral vascular disease was more frequent in subjects with diabetes, but not in those with impaired glucose tolerance. When the subjects with impaired glucose tolerance on a single test were reclassified according to the results of a separate glucose tolerance test, the prevalence of coronary heart disease increased significantly with increasing degrees of glucose intolerance. Subjects with impaired glucose tolerance on both tests had an adjusted odds ratio of coronary heart disease of 0.90 (95% CI 0.42-1.94) compared with normal subjects. The excess of macrovascular disease in subjects with impaired glucose tolerance may result, at least in part, from the admixture of 'false negative diabetics' in that class.

Improvement in glucose tolerance after one year of follow-up in a Hindu community in Africa

Oral glucose tolerance was studied following a 75 g glucose load in 108 (82.4%) of 131 male and 110 (79.1%) of 139 female members of a Hindu subcommunity aged 15 years and over in Dar es Salaam. One year later, the glucose tolerance tests were repeated in 93 (86.1%) and 93 (84.5%) of the 108 male, and 110 of the female subjects, respectively. In the first survey, 25 (26.9%) of the 93 male and 24 (25.8%) of the 93 female subjects had impaired glucose tolerance (IGT), 6 (6.4%) and 15 (16.1%), respectively, had diabetes mellitus; and 62 (66.7%) and 54 (58.1%), respectively, had normal glucose tolerance. In the repeat survey, of the 93 male and 93 female subjects, 8 (8.6%) and 7 (7.5%) had IGT, 4 (4.3%) and 10 (10.8%) had diabetes; and 81 (87.1%) and 76 (81.7%) were normal, respectively. Of the 21 subjects diagnosed as having diabetes in the first survey, 13 (61.9%) continued to show diabetic glucose tolerance; 4 (19%) IGT and 4 (19%) had normal glucose tolerance with no gender difference. One (1.6%) of the 62 male subjects and none of the 54 females with normal glucose tolerance in the first survey progressed to IGT, while the remainder retained normal glucose tolerance. Diabetes and IGT rates in both surveys were higher for the older than the younger persons. A significant fall in mean fasting and post-75 g blood glucose levels, and in mean systolic and diastolic pressure levels was observed between the first and second surveys in both genders. There was, however, no significant difference in body mass index (BMI), serum total cholesterol and triglyceride levels between surveys, suggesting that major dietary changes had not taken place. Male subjects who showed persistent IGT had significantly lower mean level of body mass index (kg/m2) than subjects who reverted to normal, whilst for the whole group those who had persistent IGT were older. It is tempting to speculate that these changes were due to community action. However, in view of the lack of change in weight and lipids and similar results in other communities in Tanzania when retested at 1 week, further studies are needed to establish the significance of the findings.

Unexplained variability of glycated haemoglobin in non-diabetic subjects not related to glycaemia

We have studied levels of glycated haemoglobin in a sample of 223 people aged over 40 years without known diabetes mellitus screened in a community study. Each had a glucose tolerance test and glycated haemoglobin measured by four methods - agar gel electrophoresis with and without removal of Schiff base, affinity chromatography and isoelectric focusing. The correlation coefficients between 2 h blood glucose and levels of glycated haemoglobin were between 0.43 and 0.64. This poor correlation was not explained on the basis of assay or biological variability of either 2 h blood glucose or glycated haemoglobin. Multiple regression analysis showed that other assays of glycated haemoglobin contributed to the variance of any single glycated haemoglobin value by 0.1%-52.9% (median 12.8%) compared to the variance of 18.6%-41.4% (median 30.8%) explained by 2 h blood glucose alone, suggesting that in a non-diabetic population, the degree of glucose intolerance may explain only one third of the variance of glycated haemoglobin levels, but other factors operate to produce consistent changes in levels of glycated haemoglobin. Investigation of 42 subjects with consistently high (20 subjects) or low (22 subjects) levels of glycated haemoglobin relative to their 2 h blood glucose level showed no difference in age, gender, body mass index, haemoglobin levels or smoking, although 50% of low glycators had impaired glucose tolerance. Neither ambient blood-glucose levels, as estimated on two five-point blood-glucose profiles, nor dietary intake of carbohydrate, starch, sugars, fibre or alcohol, explained the difference between high and low glycators. The determinants of the consistent interindividual differences in levels of glycated haemoglobin in non-diabetic subjects remain to be determined.