Is serum fructosamine a clinically useful test?

Ethnic differences in diabetic retinopathy

AIMS/HYPOTHESIS

To compare the prevalence of diabetic retinopathy in European, Maori and Pacific peoples with diabetes.

METHODS

Biomedical assessment and retinal examination, using photography where possible, was undertaken in 458 (67.5% of eligible) randomly selected household survey participants with known diabetes (168 Europeans, 144 Maori, 149 Pacific people). Glycaemia was measured by glycated haemoglobin, fructosamine and random glucose.

RESULTS

In those with Type 2 diabetes, the prevalence of moderate or more severe retinopathy was 4.0% in Europeans, 12.9% in Maori and 15.8% in Pacific people (P = 0.003). There was no significant ethnic difference in the prevalence of retinopathy overall or in that of macular disease. Cataracts were more common in Pacific people (19.3%, 16.4%, 36.6%, respectively, P < 0.001). After adjusting for diabetes duration and ethnicity, Type 1 diabetes was associated with 5.3(1.7-16.4)-fold increase in moderate or more severe retinopathy. Although Maori and Pacific people with Type 2 diabetes were more hyperglycaemic, with higher systolic and lower diastolic blood pressure, in the logistic regression analysis, moderate or more severe retinopathy was associated with diabetes duration, insulin therapy, ethnicity and the extent of renal disease, but not glycaemia.

CONCLUSIONS

These data demonstrate that moderate or more severe retinopathy is more common in Polynesians than Europeans. The reasons for this are unclear, but may be related to long-standing hyperglycaemia.

Glycemic monitoring in diabetics with sickle cell plus beta-thalassemia hemoglobinopathy

OBJECTIVE

To report a case of diabetes management in a patient with a hemoglobinopathy that caused her clinician to seek a different measure of glycemic control, fructosamine, rather than glycosylated hemoglobin (HbA1c).

CASE SUMMARY

A 53-year-old African American woman presented with a past medical history of type 2 diabetes, hypertension, seizure disorder, rheumatoid arthritis, and sickle cell disease plus beta-thalassemia. She reported fasting blood glucose values ranging broadly from 50 to 320 mg/dL, yet her HbA1c result remained steady in a low range of <6%. A measure of fructosamine returned elevated at 340 micromol/L (reference range 200-300).

DISCUSSION

We believe that this patient's hemoglobinopathy resulted in falsely low levels of HbA1c, and we substantiate this interpretation with the patient's self-monitored blood glucose values from home that appeared higher and inconsistent with the HbA1c results. Although few reports on using the measure of fructosamine appear in the literature, this patient's high fructosamine result supports fructosamine as the more appropriate measure of glycemic control.

CONCLUSIONS

Serum fructosamine levels may be considered as an appropriate laboratory measurement when monitoring long-term glycemic control in patients with type 2 diabetes mellitus and sickle cell disease.

Determination of reference values for a novel ketoamine-specific fructosamine assay for assessment of diabetic glycemic control

BACKGROUND

Intensive monitoring to improve glycemic control is essential for effective management of diabetes and reduction of long-term morbidity and pathology. Measurement of glycated serum proteins (fructosamine) allows more frequent assessment (monthly) of glycemic control than the 2- to 3-month window of the traditional glycated hemoglobin (HbA1c) assay. In response to concerns about assays designed to measure glycated serum proteins based on the nitroblue tetrazolium (NBT) methodology, a novel assay to measure glycated serum proteins has been developed based on the specific oxidation of the ketoamine bonds within the glycated proteins.

METHODS

Reference range values for this new, enzymatic glycated-serum-protein assay (GlyPro; Genzyme Corporation, Cambridge, MA) are reported.

RESULTS

The GlyPro reference range is lower and shows close correlation with ranges reported for the NBT assay. The 95% overall reference range was 122 to 236 mumol/L.

CONCLUSIONS

GlyPro is a reliable, accurate assay and correlates well with the NBT assay for the measurement of glycated serum proteins. The assay may be useful in the short-term assessment of diabetes control, a necessary complement to long-term control as assessed by hemoglobin A1c (HbA1c) assays.

Effect of protein intake on glycaemic control and renal function in type 2 (non-insulin-dependent) diabetes mellitus

Recent clinical investigations have suggested that dietary protein intake may modulate the progression of diabetic nephropathy and influence glycaemic control in Type 2 (non-insulin-dependent) diabetes mellitus. Twelve normotensive Type 2 diabetic patients with microalbuminuria took part in a randomized cross-over trial of a 3-week high protein diet (2.0 g/kg.desirable weight per day) and a 3-week moderate protein diet (0.8 g/kg desirable weight per day) to test the simultaneous effect of protein intake modulation on glycaemic control and renal function. Both diets were isoenergetic and the moderate protein diet was supplemented with calcium and phosphate. Renal function and glycaemic control were evaluated at the beginning and at the end of each diet. The moderate protein diet reduced the urinary albumin excretion rate, glomerular filtration rate, creatinine clearance, and proteinuria without adversely affecting glycaemic control; fasting glycaemia and the ratio of fructosamine to proteins were significantly reduced. The high protein diet induced similar improvements in glycaemic control but small changes in renal function.

Relationship of lipid peroxides to diabetic complications. Comparison with conventional laboratory tests

One hundred and seventy-three Arab patients with non-insulin-dependent diabetes mellitus (NIDDM) and 51 controls were examined. The routine laboratory tests of fasting blood sugar (FBS), glycosylated hemoglobin (HbA1c), fructosamine (FRA), and triglycerides (TG) were compared with lipid hydroperoxides (LHP) as detected by the thiobarbituric acid (TBA) method, which measures total TBA reacting substances (TBARS). All routine laboratory measures were elevated in the patient population. In the case of LHP, values in NIDDM were 491 +/- 183 mumol/L for men and 507 +/- 183 mumol/L for women, as compared with pooled normal values of 275 +/- 85 mumol/L. Seven patients with NIDDM undergoing hemodialysis were also elevated above normal (441 +/- 97 mumol/L). Comparisons between LHP and the other biochemical parameters indicated a positive statistical correlation with triglycerides (p less than 0.001); FBS, HbA1c, and FRA (p greater than 0.01). Patients with NIDDM on dietary control had somewhat lower LHP levels (441 +/- 135 mumol/L) than those receiving insulin (519 +/- 206 mumol/L), or oral hypoglycemic agents (518 +/- 177 mumol/L). Dietary maintenance also resulted in reduced FBS and HbA1c levels. Subdivision of patients according to duration of disease and by nationality showed that Kuwaiti nationals had slightly higher LHP values than did patients of other Arabic origin. Women patients (Kuwaiti and non-Kuwaiti) with NIDDM disease duration of greater than 10 years, had LHP levels above those of males (551 +/- 245 versus 478 +/- 126 mumol/L) and, as a group, showed significant enhancement of retinal complications (85.5% versus 55%). A statistically significant trend (p less than 0.08) could be demonstrated between the prevalence of retinopathy and increasing serum LHP levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the real-time use of glycosylated haemoglobin and plasma fructosamine in the diabetic clinic

The within-clinic use of glycosylated haemoglobin (HbA1) and plasma fructosamine results in assessing blood glucose control and clinical management was compared in 1030 diabetic patients. The physician initially reviewed the patient with one randomly allocated measure (HbA1 or fructosamine) and completed a questionnaire concerning perception of blood glucose control, alteration to diet, alteration to medication, referral for diabetes education, and follow-up interval. The patient was then re-assessed using the second measure and the questionnaire repeated. Discordance rates for the study end-points, judged as binary outcomes, were: blood glucose control 15%; alteration to diet 7%; alteration to medication 9%; referral for education 3%; follow-up interval 4%. A significantly greater number of patients were rated as poorly controlled with HbA1 than with fructosamine (p less than 0.001) and were, in consequence, more frequently recommended alteration to diet and medication, referral for education and shorter follow-up interval; the rate of discordance for at least one of the management decisions was 16%. Multifactorial analysis showed that discordant management was dependent on the reviewing physician (p less than 0.001) and a history of cardiovascular disease (p less than 0.01); but neither type of diabetes, nor presence of nephropathy or variant haemoglobins, nor plasma glucose concentration, significantly influenced the likelihood of a discordance. Replacing HbA1 with fructosamine in the diabetic clinic may result in significant differences in the physician's perception of blood glucose control and in the management of patients.

Fructosamine as a screening-test for gestational diabetes mellitus: a reappraisal

Fructosamine, glycosylated hemoglobin (HbA1c) and serum total proteins were measured in normal nondiabetic pregnant women (n = 170) at three stages of pregnancy (14-18, 24-28, and 32-40 weeks of gestation). No significant correlation was found between fructosamine and either HbA1c or total plasma proteins. Only early in pregnancy (less than 20 weeks of gestation) was a correlation found between fructosamine and fasting blood glucose (r = 0.40, P less than 0.05). There was also no correlation between either tests (i.e. fructosamine and HbA1c) and fetal birthweight. The value of fructosamine measurement in the detection of diabetes in pregnancy was further tested in a group of high-risk patients (n = 98) for developing carbohydrate intolerance. It is concluded that fructosamine has limited value as a screening test for gestational diabetes mellitus, particularly for the mild form of the glucose intolerance.

Longitudinal changes in serum fructosamine do not parallel those in glycated haemoglobin in young adults with insulin-dependent diabetes

In 93 adolescent and young adult patients with type 1 diabetes (163 paired comparisons) changes in fructosamine concentration correlated poorly with changes in HbA1 (r = 0.53); this correlation was no better if fructosamine values were adjusted for serum albumin by calculating a fructosamine/albumin index, F.A.I. (155 pairs, r = 0.50). These correlation coefficients were lower than those for cross-sectional comparisons (HbA1 vs. fructosamine, r = 0.74; HbA1 vs. F.A.I., r = 0.80). One-way analysis of variance showed that values of HbA1, fructosamine and F.A.I. all tended to increase as glycaemic control, judged by the clinician, worsened (P less than 0.001). HbA1 correlated better with clinical assessment than did either uncorrected fructosamine or F.A.I. We conclude that changes in fructosamine from one clinic visit to the next do not provide a basis for changing therapy. Clinical assessments tend to agree with values for HbA1, which may be more reliable than fructosamine because of its longer biological half life.

Maternal serum fructosamine and maternofetal glucose and insulin homeostasis in normal pregnancy

Well-defined normal values are necessary to identify pregnancies complicated by gestational diabetes (GD) and thus further reduce perinatal morbidity and mortality from this condition. The present study defined the range for the oral glucose tolerance test (oGTT) in 2578 pregnancies. After exclusion of abnormal results 822 randomized patients were used to define normal values for fructosamine, HbA1c, insulin, glucose and C-peptide in the maternal serum; insulin, glucose and fructosamine in the amniotic fluid; and insulin, glucose, C-peptide and fructosamine in the cord blood.

Clinical utility of assays of glycosylated haemoglobin and serum fructosamine compared: use of data on biological variation

Assessment of the relative clinical usefulness of glycosylated haemoglobin (HbA1) and serum fructosamine is complicated by their markedly different half-lives. They have therefore been compared using a number of indices derived from data on biological variation, as applied in a study of blood glucose control in newly diagnosed diabetic patients. The within-subject (CVI) and between-subject (CVG) variation of fructosamine and HbA1 were assessed in 8 stable diabetic patients. A slightly smaller relative change, or critical difference, is required between serial HbA1 results than between fructosamine results before a significant change can be said to have occurred. The heterogeneity of within-subject variance is also less for HbA1, rendering the critical difference more generally applicable. HbA1 may therefore be more appropriate for long-term monitoring. Monitoring of blood glucose control of a group of 26 newly diagnosed diabetic patients before the commencement of therapy and 1, 2, and 3 months later by serum fructosamine or HbA1 provided very similar information. Fructosamine responds more rapidly with changes of blood glucose control. However, whether this confers any clinical advantage will depend upon the frequency of testing.

Screening for diabetes: does measurement of serum fructosamine help?

The diagnostic sensitivity and specificity for diabetes of serum fructosamine levels and fasting venous blood glucose concentrations were compared in 613 subjects during a diabetes community screening programme of 1049 adult Muslim Asians in Dar es Salaam, Tanzania. Using WHO (1985) criteria 228 had impaired glucose tolerance (IGT), 41 had previously been diagnosed as having diabetes while 32 had newly recognized diabetes. The mean (+/- SD) serum fructosamine levels were 20.9 +/- 3.2, 21.6 +/- 3.2, 23.9 +/- 4.9, and 30.1 +/- 7.9 (mumol g-1 albumin) in subjects with normal glucose tolerance, IGT, newly diagnosed diabetes, and previously diagnosed diabetes, respectively (p less than 0.001 for differences between groups). The specificity of values above the mean +2SD normal was 99% for abnormal glucose tolerance with a sensitivity of only 22% for diabetes. The predictive values were 44% and 97% for positive and negative results, respectively. Very little difference from normal was found for IGT subjects. Expressing fructosamine values in absolute terms or per gram albumin made little difference to sensitivity and specificity. The sensitivity was only 32% for fasting blood glucose greater than or equal to 6.7 mmol l-1, 73% for values greater than or equal to 5.5 mmol l-1, and 100% for fasting blood glucose greater than or equal to 4.5 mmol l-1. It is concluded that both serum fructosamine and fasting blood glucose are poor screening and diagnostic tests for diabetes and for IGT, and that glucose loading is required.