Screening for diabetes: does measurement of serum fructosamine help?

Screening for diabetes in general practice

The prevalence of type 2 diabetes is rising rapidly worldwide. Evidence suggests that between one third and one half of cases are undiagnosed and patients may have preclinical disease for as long as 12 years. At diagnosis, 50% of patients have microvascular complications (retinopathy, neuropathy, or nephropathy) and patients have twice the risk of macrovascular disease compared to the background population. Screening for type 2 diabetes would allow earlier recognition of cases, with the potential to intervene earlier in the disease course, but whether this would result in improved long-term outcomes is unknown. The debate continues about who should be considered for screening, how we should screen, and whether we should screen for diabetes at all. The authors review the evidence, particularly in light of the recent position statement on diabetes screening published by the American Diabetes Association. If we do start screening for diabetes, one of the major challenges ahead is to ensure resources are in place to allow optimization of treatment for the increasing number of patients. This is important both in those found to have diabetes and in those with lesser degrees of glucose intolerance who are at high risk of developing diabetes and are at increased risk of macrovascular disease.

The prevention of type 2 diabetes--lifestyle change or pharmacotherapy? A challenge for the 21st century

Diabetes mellitus is occurring in epidemic proportions in many countries. In Australia 7.4% of people over 25 years of age have diabetes (mostly type 2) and comparable or higher prevalences have been reported in the United States and a number of Asian countries. The enormous economic and social cost of this disease makes a compelling case for prevention. Epidemiological studies have shown clearly that type 2 diabetes results from an interaction between a genetic predisposition and lifestyle factors including obesity, sedentary behaviour and both calorie excess and various dietary constituents. The natural history of type 2 diabetes includes a preceding period of impaired glucose tolerance (IGT)/impaired fasting glucose (IFG) which provides an opportunity for targeted intervention within large communities. Lifestyle intervention studies have consistently shown that quite modest changes can reduce the progression from IGT to diabetes by 50-60%. It may, however, not be possible to translate these successful findings to larger cohorts or maintain the lifestyle changes longer term. This has lead to consideration of pharmacotherapy. While small studies with sulphonylureas are inconclusive, benefits have been found for metformin, acarbose and troglitazone. Big intervention studies with ramipril, rosiglitazone, valsartan and nateglinide are underway. Pharmacological intervention raises a whole range of ethical, economic and practical issues not the least of which is the problem of long term therapy of the 'otherwise well'.

Monitoring diabetic control in developing countries: a review of glycated haemoglobin and fructosamine assays

Measurement of glycated proteins, especially haemoglobins, is now a routine procedure for monitoring previous glycaemic control in diabetic patients in the developed world. Until recently, however, the assays were sophisticated and costly and, therefore, were only rarely used in developing countries. With easier and cheaper tests now available, the measurement of glycaemic control could be also introduced into regional hospitals in developing countries. This paper reviews feasible methods for clinical laboratories with limited resources. Recent experiences from African countries are included.

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.

Effects of age and obesity on glycated haemoglobin and 1,5-anhydroglucitol in screening for type 2 diabetes mellitus

The diagnostic accuracy of glycated haemoglobin (HbA1c) and 1,5-anhydroglucitol (AG) and their association with age and obesity in the community screening for Type 2 diabetes were investigated. HbA1c and AG were measured in 368 subjects at the time of an oral glucose tolerance test (OGTT) based on WHO criteria. The impact of age and obesity on the probability of diabetes was evaluated by multivariate logistic regression analysis. Receiver operating characteristic (ROC) analysis was used to assess diagnostic accuracy of each method. The areas under ROC curves were compared for subjects aged 30-59 and 60-82 years. In the logistic analysis, age was associated with the probability of diabetes, while body mass index did not contribute to the model. The paired ROC analyses indicated that HbA1c was superior to AG only in the younger subjects. When the areas for two age groups were compared, both HbA1c and AG performed better in the younger than older subjects. We conclude that for the younger subjects, HbA1c value is highly sensitive (100.0%) and specific (90.4%) and is helpful for the diagnosis of Type 2 diabetes. On the other hand for the older subjects, both HbA1c and AG are poor screening tests in reference to the OGTT standard.

Fasting plasma glucose as a diagnostic indicator of diabetes mellitus

Among 233 patients referred for glucose tolerance test (GTT), 36.4% of 129 non-pregnant subjects were classified as diabetic, compared with only 2.9% of 104 pregnant subjects. Preliminary screening using a fasting plasma glucose upper cut-off of 7.0 mmol/l, above which the subject was classified as diabetic and a lower one of 4.4 mmol/l, below which he or she was considered normal, would have eliminated the need for 30% of GTTs and positively identified 60% of the diabetics in the non-pregnant group. Only one patient would have been significantly misclassified, possibly owing to inadequate fasting. However, little benefit would result from applying an upper cut-off to low-prevalence populations such as the pregnant group. Like other recent surveys, this study suggests that World Health Organisation diagnostic figures for fasting plasma glucose could be revised downwards to 7.0 mmol/l. Conversely, to be fairly certain that an individual is not diabetic, fasting plasma glucose must be below about 4.4 mmol/l.

Random blood glucose as a screening test for diabetes in a biethnic population

Screening asymptomatic subjects for diabetes is often undertaken using a random capillary whole blood sample for glucose estimation. The test characteristics of this method for screening were assessed using a glucose oxidase method among 3425 Europeans and 3469 South Asians who gave such a sample during the Coventry Diabetes Study, a house-to-house diabetes prevalence study. Glucose tolerance test were performed on those with a high blood glucose and 10% of others. Previously undiagnosed diabetes was found in 73 Europeans and 110 South Asians. If the random glucose was > or = 7.0 mmol l-1, 8.0% of Europeans and 6.7% of South Asians would need a further diagnostic test and the sensitivity of this cut-off was 51.7 (95.0% CI: 43.5-59.9)% in Europeans and 68.4 (60.6-76.2)% in South Asians. Sensitivity was increased in South Asians but not Europeans by defining the time since last meal (South Asians < 2 h: 83.9 (72.3-92.0)%; > or = 2 h: 54.9 (42.7-66.8)%). Sensitivity was poorest among Europeans aged > or = 65 years (40-64 years 69.0 (49.2-84.7)%, > or = 65 years 49.4 (38.2-60.6)%). Screening asymptomatic individuals using an isolated capillary random whole blood glucose measure is a poor test for diabetes, although slight improvement can be obtained among South Asians by testing within 2 h of a meal.

Problems related to definitions and epidemiology of type 2 (non-insulin-dependent) diabetes mellitus: studies throughout the world

Many studies of Type 2 (non-insulin-dependent) diabetes mellitus assume that the condition is homogeneous and clearly defined. There are, however, several problems with these assumptions. Thus, definition of Type 2 diabetes is one of exclusion of other types (insulin-dependent, malnutrition-related, gestational and other rarer types) and inevitably contains a heterogeneous group of disorders the aetiology of which is largely unclear, and separation from the insulin-dependent type can be problematic. Diagnosis is also imprecise in asymptomatic subjects due to the lack of accurate diagnostic tools and lack of clear distinction of impaired glucose tolerance. An alternative to the oral glucose tolerance test is urgently needed. Epidemiological studies of Type 2 diabetes and its complications are also fraught with difficulties due to variability of the oral glucose tolerance test, potential problems in glucose measurement, heterogeneity, population selection and problems in international comparisons due to differing age structures and life expectancy. Great care is needed in all studies of Type 2 diabetes to ensure that the groups under study are properly selected, well-defined and fully described.

Is serum anhydroglucitol an alternative to the oral glucose tolerance test for diabetes screening? The Mauritius Noncommunicable Diseases Study Group

The oral glucose tolerance test is inconvenient for diabetes screening. In clinical studies a reduced serum anhydroglucitol level has proved to be a sensitive and specific test for diabetes. A new minicolumn enzymatic method which is simple and robust makes use in population screening feasible. The aim of our study was to assess the usefulness of a single measurement of anhydroglucitol to screen for diabetes and impaired glucose tolerance. Assays were performed on samples taken from 227 Mauritian Chinese subjects at the time of glucose tolerance testing. Subjects had normal glucose tolerance (n = 82), impaired glucose tolerance (n = 76), newly diagnosed diabetes (n = 38), and known diabetes (n = 31). Anhydroglucitol concentrations (mean +/- SD) were similar for normal and impaired glucose tolerance subjects (23.7 +/- 8.2 vs 23.4 +/- 8.6 mg l-1). Although the differences between normal and newly diagnosed diabetes (15.0 +/- 11.0 mg l-1) and known diabetic subjects (11.8 +/- 10.6 mg l-1) were significant (p < 0.001), diagnostic sensitivity and specificity were poor. We conclude that measurement of serum anhydroglucitol is not suitable for screening for the diagnoses of impaired glucose tolerance and diabetes.

Fructosamine in diabetes screening of the elderly

The use of serum fructosamine in diabetes detection was investigated during a diabetes survey performed with a modified oral glucose tolerance test (MOGTT) on 742 residents of the Melton Mowbray area aged between 65 and 85 years. Subjects were tested in the morning and remained at rest. MOGTT results were classified by WHO criteria. The fructosamine concentration was measured in a random sub-group of 264 normal subjects and had a Gaussian distribution (mean = 1.67 mmol/L, SD = 0.126 mmol/L). In the survey as a whole 25 new diabetics were found of which 23 had fructosamine measured; 17 had values above the 95th percentile and four more had values above the 90th percentile. We have found fructosamine concentration to be a useful screen for diabetes but this may be dependent upon the standardized sampling procedure used, and the population studied.

Serum fructosamine is not a useful screening test for gestational diabetes

Serum fructosamine was measured in 569 samples of pregnant women without gestational diabetes. We defined abnormal fructosamine as mean + 2SD, and analysed its potential value to detect patients with gestational diabetes diagnosed with current screening criteria. We found serum fructosamine to be an insensitive parameter: Measured at the time of a positive 50 g glucose screening, SF would have detected 4/48 gestational diabetes.