Clinical evaluation of serum fructosamine in monitoring elderly outpatient diabetics

Diabetes in elderly adults

Diabetes is common in the elderly population. By the age of 75, approximately 20% of the population are afflicted with this illness. Diabetes in elderly adults is metabolically distinct from diabetes in younger patient populations, and the approach to therapy needs to be different in this age group. Diabetes is associated with substantial morbidity from macro- and microvascular complications. Several lines of evidence suggest that optimal glycemic control and risk factor modification can substantially reduce the risk of complications in elderly patients. In the past, treatment options were limited. However, recent studies have delineated several new and exciting therapeutic opportunities for elderly patients with diabetes.

Clinical validity of a self-test fructosamine in outpatient diabetic management

BACKGROUND

Measurement of glycated hemoglobin and hemoglobin A1c (HbA1c) is now well established as the best means of measuring overall glucose control in managing diabetes. Other glycated serum protein assays reflecting recent glycemic control, e.g., glycated albumin and glycated protein (fructosamine), have also been validated in clinical studies. Regardless of the method, the expense and inconvenience of laboratory testing of blood samples may contribute to the well-documented underutilization of clinical glycated protein assessment. Accordingly, a rapid, inexpensive fingerstick test of fructosamine has been developed. This study cross-sectionally and prospectively assesses the clinical validity of fingerstick fructosamine versus laboratory determination.

METHODS

Fifty-one subjects (18 control, 33 with diabetes) participated in a cross-sectional study and 20 subjects with type 2 diabetes participated in a prospective, 6-week study with clinical intervention consisting of glipizide gits or metformin in mono- and combination therapy. Subjects had weekly laboratory determination of serum fructosamine, glycated hemoglobin, and fasting glucose; fingerstick fructosamine was obtained at each clinic visit.

RESULTS

Fingerstick fructosamine was shown to correlate highly to laboratory fructosamine (r = 0.80, p < 0.001) and glycated hemoglobin (r = 0.81, p < 0.001). In the clinical intervention study subjects, significant decreases in fasting glucose (p < 0.001), laboratory fructosamine (p < 0.001), and fingerstick fructosamine (p < 0.001) were noted compared to baseline. The subject's self-test fingerstick fructosamine mirrored laboratory testing of fructosamine in detection of changes in clinical glucose control.

CONCLUSIONS

This study demonstrates that fingerstick fructosamine correlates well to laboratory assessment of fructosamine and glycated hemoglobin. The patient self-test fructosamine provides the same clinical information as laboratory assessment.

Non-insulin-dependent diabetes mellitus in the elderly

The prevalence of non-insulin-dependent diabetes mellitus dramatically increases with age. Older diabetic subjects have an increased frequency of complications from diabetes compared with their younger counterparts and higher morbidity and mortality rates compared with age-matched non-diabetic controls. Elderly patients with diabetes are generally treated following the same approach as in younger patients: dietary therapy first, followed by oral hypoglycaemic agents and ultimately insulin. However, several specificities should be pointed out. Changes associated with ageing may affect the pharmacokinetics and pharmacodynamics of both sulphonylureas (increasing the risk of severe hypoglycaemia) and biguanides (increasing the risk of lactic acidosis). The best insulin regimen in old age is not known, but a twice-daily injection of a pre-mixed insulin preparation is usually recommended. Goals of therapy must be realistic and not cause disabling side-effects. The general practitioner plays a crucial role in the care of elderly diabetic patients, but access to a multidisciplinary specialized team may be necessary.

Diabetes in the elderly

Diabetes affects at least 20% of the population over the age of 65. Half of these patients are unaware that they have the disease. Diabetes in middle-aged subjects is characterized by an impairment in glucose induced insulin release, increased fasting hepatic glucose output and resistance to insulin mediated glucose disposal. In contrast, diabetes in the elderly is primarily associated with insulin deficiency. The presentation of diabetes in the aged is often non-specific. The elderly have an increased frequency of complications from diabetes. They are particularly susceptible to hypoglycaemia, because of reduced awareness of hypoglycaemic warning symptoms and altered release of counterregulatory hormones. Although no data are yet available from randomized controlled trials, there is abundant epidemiological evidence to suggest that adequate control of blood glucose can be expected to reduce the risk of long-term complications. A team approach is ideal for the management of the elderly patient with diabetes. Little data is available on which to base a diet and exercise prescription for elderly patients. Gliclazide appears to be the sulphonylurea of choice in the aged because it is associated with a lower frequency of hypoglycaemic reactions. Urine glucose testing is unreliable, and capillary glucose monitoring is preferred. Fructosamine may prove to be superior to haemoglobin A1C for monitoring long-term control.

Serum fructosamine as a screening test for diabetes in the elderly: a pilot study

OBJECTIVE

To determine the value of serum glycated protein, measured as serum fructosamine, as a screening test for diabetes in the elderly.

DESIGN

Cross-sectional pilot study.

SETTING

Ambulatory research clinic in university setting.

PATIENTS

One hundred fifty-seven consecutive community-dwelling participants in the Cardiovascular Health Study, average age 71.8 + 5 (mean +/- SD, range 65-88 years).

MEASUREMENTS

Serum fructosamine levels (first and second generation assay) were obtained. All subjects who did not have a diagnosis of diabetes were given a 75-g glucose tolerance test (GTT).

RESULTS

Twenty-six subjects (17%) (10 previously diagnosed, 16 undiagnosed and asymptomatic) had diabetes mellitus, and 38 subjects (24%) had impaired glucose tolerance by history or by the GTT (WHO criteria). Only the 16 asymptomatic diabetics were included in the analysis for the pilot study. There was a significant difference in the fasting fructosamine level between non-diabetics and asymptomatic diabetics for the first generation (2.06 +/- .21 vs 2.53 +/- .49 mMol/L, P < 0.0015) and second generation assay (221 +/- 27 vs 269 +/- 48 mMol/L, P < 0.0012). Receiver operator curves were constructed to evaluate the test characteristics of serum fructosamine. Using a point of > or = 2.3 mMol/L for the first-generation assay, the sensitivity to detect asymptomatic diabetes was 75%, specificity 83%, and positive predictive value 35%. To detect both diabetes and impaired glucose tolerance using a cutpoint of > or = 2.3 mMol/L, the sensitivity was 24%, specificity 95%, and positive predictive value 68%. Employing a cut point of 250 muMol/L for the second generation assay, the sensitivity to detect diabetes was 81%, specificity 87%, and positive predictive value 43%. However, to detect diabetes and glucose intolerance using the second generation assay, the sensitivity was 39% and specificity was 86%.

CONCLUSION

This study demonstrated that a single measurement of either first or second generation fructosamine showed promise as a screening test for diabetes, but not impaired glucose tolerance, in older people.

Determination of furosine in biomedical samples employing an improved hydrolysis and high-performance liquid chromatographic technique

Traditionally, the most sensitive and specific determination of non-enzymatic protein glycation has involved an 18-24-h acid hydrolysis in order to generate the compound furosine, which has been detected employing reversed-phase h.p.l.c. In this study, we have reported that significant quantities of furosine can be generated with much shorter hydrolysis times employing a 90-min vapor-phase acid hydrolysis procedure. The furosine generated by vapor-phase hydrolysis is then quantitated by pulsed amperometric detection using anion-exchange high-performance liquid chromatography. Employing this method, we were able to show that furosine generated from acid hydrolysis of purified hepatic membranes in a diabetic and non-diabetic animal model agreed with traditional methods assessing total glycated protein (i.e., boronate affinity methods).

The management of diabetes mellitus in older individuals

Nearly 50% of individuals with type II diabetes mellitus are over the age of 65 years. There are numerous reasons to maintain blood glucose levels below 11.1 nmol/L (200 mg/dl) in older persons, and there are a number of changes often seen with advancing age that persons, and there are a number of changes often seen with advancing age that may interfere with the management of diabetes mellitus, e.g. hypodipsia, anorexia, visual disturbance, altered renal and hepatic function, depression, impaired basoreceptor response and multiple medications. Hyperglycaemia appears to produce cognitive impairment which may lead to poor compliance. It is often difficult to manipulate diet in older people, and in fact dietary changes can lead to severe protein energy malnutrition. High maximum voluntary oxygen intake has been correlated with increased glucose disposal, but there is little evidence that physical exercise can improve diabetic control in the elderly. Oral sulphonylurea hypoglycaemic agents are extremely useful in the treatment of diabetes in these patients, but it should be remembered that they are more liable to develop hypoglycaemia than are younger diabetics. The role of metformin in the management of older diabetic patients is poorly studied. Many older persons can cope well with insulin therapy, but those with visual disturbances often make errors when drawing up insulin and require special attention. Combination therapy of insulin with oral hypoglycaemic agents is not recommended in this group of patients, and serum fructosamine is preferred to glycated haemoglobin to monitor control. Successful management of elderly diabetic patients thus requires an interdisciplinary team approach.