The Measurement of Haemoglobin A1c by isoelectric focussing in diabetic patients

Pre-mixed insulin delivered by disposable pen in the management of children with diabetes

Pre-mixed insulin preparations are being used increasingly in the management of children with IDDM. Recently this form of insulin has been produced in a disposable insulin pen device. An open randomized 3-month crossover study was conducted to compare glycaemic control on a self-titrating insulin regimen with a pre-mixed (30:70) preparation, both given twice daily. The pre-mixed preparation was delivered by disposable pen. Forty children (age range 7-16 yr) entered the study. Mean +/- SEM glycosylated haemoglobin (HbA1 %) at the start of the study (13.1 +/- 0.6) compared with values at the end of the self-titrating (11.8 +/- 0.5) and pre-mixed periods (12.5 +/- 0.5), as well as blood glucose profiles taken at 3-weekly intervals, showed no significant change. Fourteen of the children were on insulin ratios other than 30:70 (range 10:90 to 50:50) and were unaffected by the switch (HbA1 at the start of the study 12.7 +/- 1; at the end of the self-titrating 11.5 +/- 0.8; and pre-mixed period 12.5 +/- 0.8). Twenty-one children continued on the pen for a further 12 months with no deterioration in control (HbA1 at the beginning and end of this period being 11.9 +/- 0.7 and 11.0 +/- 0.7, respectively). The children (95%) preferred the disposable pen and pre-mixed insulin regimen. Switching to pre-mixed insulin, while not improving, has no detrimental effect on glycaemic control.

Glomerular and tubular proteinuria in type 1 (insulin-dependent) diabetic patients with and without retinopathy

We compared the urinary excretion of albumin, transferrin, N-acetyl-beta-D-glucosaminidase and alpha-1-microglobulin in 78 Type 1 (insulin-dependent) diabetic patients: 39 with retinopathy and 39 without. The two groups were matched for age, sex and duration of diabetes. The patients with retinopathy had increased excretion (median and range) of albumin [1.7(0.3-399.1) versus 1.0(0.3-116.6) mg/mmol creatinine, P less than 0.05], transferrin [114.2 (4.1-37126.2) versus 33.4 (1.0-4176.7) micrograms/mmol creatinine, P less than 0.01] and N-acetyl-beta-D-glucosaminidase [23.8 (1.1-119.1) versus 15.0 (0.1-65.1) mumol/h/mmol creatinine, P less than 0.05] but not alpha-1-microglobulin. Transferrin excretion correlated with albumin excretion. The prevalence of increased transferrin excretion (transferrinuria) was greater than that of microalbuminuria in patients both with and without retinopathy (P less than 0.01 in both cases). Urinary transferrin seems likely to be predominantly of glomerular origin and merits prospective longitudinal evaluation as a potential index of the microangiopathic process.

Contrasting fibrinolytic responses in type 1 (insulin-dependent) and type 2 (non-insulin-dependent) diabetes

To study fibrinolysis in relation to microvascular diabetic complications, 20 control subjects were compared with 50 Type 1 (insulin-dependent) diabetic patients of similar age, 20 with no complications, 17 with laser-treated retinopathy, and 13 with neuropathy and retinopathy. None were smokers, hypertensive or had macrovascular disease. Pre- and post-venous occlusion blood samples for tests of fibrinolysis were taken. Median (interquartile range) basal tissue plasminogen activator (t-PA) activity was lower in control subjects (100 (less than 100-100) IU l-1) than diabetic patients (uncomplicated 145 (100-280) IU l-1, p = 0.015; retinopathy 180 (100-228) IU l-1, p = 0.037; neuropathy 210 (125-310) IU l-1, p = 0.004, respectively). Basal t-PA inhibition (PAl-1 activity) was higher in control subjects (5.9 (4.5-9.5) kIU l-1) than diabetic patients (uncomplicated 4.0 (3.3-5.0) kIU l-1, p = 0.001; retinopathy 4.5 (3.1-6.3) kIU l-1, p = 0.058; neuropathy 4.0 (3.0-5.4) kIU l-1, p = 0.015, respectively). Post-venous occlusion t-PA antigen was higher in control subjects (10.2 (7.3-15.1) micrograms l-1) than neuropathic patients (5.5 (4.9-7.3) micrograms l-1, p = 0.004). Other tests showed a consistent, but non-significant, trend towards increased basal fibrinolysis in the Type 1 diabetic patients. The results indicate that Type 1 diabetic patients have enhanced basal fibrinolysis. The diminished response to venous occlusion in neuropathic patients is consistent with an endothelial cell defect.(ABSTRACT TRUNCATED AT 250 WORDS)

Metformin causes a reduction in basal and post-venous occlusion plasminogen activator inhibitor-1 in type 2 diabetic patients

The effects of metformin on the fibrinolytic system were studied pre- and post-venous occlusion in 38 Type 2 diabetic patients in a double-blind, placebo-controlled trial. After a 3-week run-in period, 21 patients received metformin and 17 placebo, for 6 weeks. In the metformin-treated patients basal plasminogen activator inhibitor-1 antigen (PAI-1Ag) fell from 57.4 micrograms l-1 before treatment to 36.1 (p less than 0.05) and 41.0 micrograms l-1 (p less than 0.01) after 3 and 6 weeks therapy. In this group post-venous occlusion PAI-1Ag also fell after 3 weeks (p less than 0.002) and 6 weeks (p less than 0.05) treatment. There were no changes in either basal or post-venous occlusion concentrations of PAI-1Ag in the placebo treated group. The fall in PAI-1Ag was not associated with an increase in basal plasminogen activator activity (PAA) which remained unchanged in both groups. Post-venous occlusion values for PAA in the metformin treated patients were increased at 3 weeks (p less than 0.05) although there was no difference at 6 weeks.

Medial arterial calcification and diabetic neuropathy

The aim of this study was to detect linear arterial calcification (Mönckeberg's sclerosis) localized in feet, ankles, legs, knees and hands in an attempt to correlate the extent of calcification with the presence and severity of autonomic neuropathy as well as with microangiopathy (proliferative retinopathy, proteinuria greater than 200 mg/die) and peripheral neuropathy. Typical linear calcification were observed in 37 out of 41 (90.2%) patients with autonomic neuropathy and in none of those without autonomic neuropathy (p less than 0.001). These 37 patients were divided into two subgroups by cluster analysis: Subgroup A, including 18 subjects with calcification length ranging from 8 to 26 cm and moderate autonomic neuropathy, and Subgroup B, including 19 subjects with calcification length between 58 and 126 cm and severe autonomic neuropathy (p less than 0.0001 by Spearman's test). No difference in the length of arterial calcification was detected between patients with proteinuria greater than 200 mg/24h and/or proliferative retinopathy and patients without these complications. A possible relationship between arterial calcification and peripheral neuropathy is difficult to evaluate; in fact, the majority of subjects having autonomic neuropathy had peripheral neuropathy, too. Vice versa, around 10% of patients without peripheral neuropathy but with autonomic neuropathy did not have Mönckeberg's sclerosis. Autonomic neuropathy is the principal factor responsible for calcification of the arterial media, and in addition the severity of the neuropathy, rather than the patient's age or the known disease duration seems to determine the extent of calcification.

Microproteinuria in type 2 diabetes mellitus from diagnosis

Glomerular and tubular microproteinuria precede the development of overt nephropathy in Type 1 diabetes mellitus. However, in Type 2 diabetes urinary protein excretion and its relationship to diabetic nephropathy has not been clearly characterized. Twenty consecutive, newly diagnosed patients with Type 2 diabetes, whose urine was Albustix-negative and sterile on culture, were studied. Two timed overnight urine samples were collected at diagnosis, and after 2 months and 2 years, and excretion rates of albumin, alpha-1-microglobulin and N-acetyl-beta-D-glucosaminidase were calculated. HbA1c fell from 12.1 +/- 2.4% at diagnosis to 9.5 +/- 1.5% at 2 months and 9.6 +/- 2.2% at 2 years. Albumin excretion rate fell marginally from 6.5 (2.1-242.5) micrograms min-1 at diagnosis to 5.5 (1.7-274.0) micrograms min-1 at 2 months (p less than 0.05) rising again to 6.1 (1.9-201.7) micrograms min-1 at 2 years. alpha-1-Microglobulin excretion rate fell from 13.5 (3.6-59.9) micrograms min-1 at diagnosis to 8.4 (2.9-16.1) micrograms min-1 at 2 months and 8.8 (1.8-54.1) micrograms min-1 at 2 years (both p less than 0.05). Albumin excretion rate was found to correlate significantly with creatinine clearance at diagnosis (rs = 0.61, p less than 0.005), though not subsequently. In contrast, excretion rates of alpha-1-microglobulin and N-acetyl-beta-D-glucosaminidase correlated with HbA1c (rs = 0.68 and 0.66, respectively, p less than 0.005 at diagnosis and rs = 0.57 and 0.53, p less than 0.05 subsequently in both cases).(ABSTRACT TRUNCATED AT 250 WORDS)

Increased urinary excretion of transferrin in children with type 1 diabetes mellitus

Urinary transferrin excretion was measured by radioimmunoassay in 74 children with Type 1 diabetes mellitus and in 40 normal children, and compared with urinary excretion of albumin, alpha-1-microglobulin, and N-acetyl-beta-D-glucosaminidase. Urinary transferrin excretion was significantly elevated in diabetic (median (range) 186 (18-1671) mg mol-creatinine-1) compared with normal (85 (27-668) mg mol-creatinine-1) children (p less than 0.001). Seventeen diabetic children had transferrin excretion above the 95th centile for normal children. In contrast there was no significant increase in urinary albumin excretion in the diabetic children although 8 had urinary albumin excretion which exceeded the 95th centile for normal children (6 of these 8 patients having coexistent urinary hyperexcretion of transferrin). Urinary transferrin excretion correlated significantly with urinary albumin excretion in both normal (rs = 0.62, p less than 0.001) and diabetic (rs = 0.61, p less than 0.001) children. The indices of proximal renal tubular function (urinary excretion of alpha-1-microglobulin and N-acetyl-beta-D-glucosaminidase) correlated significantly with transferrin excretion in both diabetic (rs = 0.43 and rs = 0.41, p less than 0.001) and normal (rs = 0.40, p less than 0.02 and rs = 0.53, p less than 0.001) children, but not with albumin excretion (rs = 0.20, p greater than 0.05 and rs = 0.22, p greater than 0.05). In addition urinary transferrin excretion significantly correlated with urinary glucose concentration (rs = 0.34, p less than 0.007) in Type 1 diabetic children. The discrepancy in urinary excretion of transferrin and albumin may reflect impaired proximal renal tubular reabsorption of transferrin and/or altered glomerular basement membrane selectivity for the two proteins.

The effect of aldose reductase inhibition on erythrocyte polyols and galactitol accumulation in diabetic patients

Erythrocyte sorbitol level has previously been used as a measure of the efficacy of aldose reductase inhibitors, but its value is limited by fluctuations related to variations in blood glucose concentration. The aim of the study was to compare sorbitol content with the ability to accumulate galactitol during ex vivo incubation with galactose, of erythrocytes taken from diabetic patients following administration of a single 600 mg dose of the aldose reductase inhibitor, ponalrestat. Twelve patients were studied in a placebo-controlled crossover trial. Blood glucose levels were not statistically different during the placebo and ponalrestat treatment periods except at 1 h after the dose was taken (10.6 +/- 6.7 vs 7.7 +/- 4.6 mmol l-1 (+/- SD), p less than 0.05). Ponalrestat reduced erythrocyte sorbitol concentrations compared with placebo at 3, 5 and 7 h (0.82 +/- 0.36, 0.69 +/- 0.23, and 0.83 +/- 0.35 mg l-1 vs 1.79 +/- 0.67, 1.68 +/- 0.65, and 1.57 +/- 0.59 mg l-1 respectively, p less than 0.005) and 24 h post-dose (1.57 + 0.45 vs 2.01 + 0.73 mg l-1, p less than 0.05). Ponalrestat also reduced erythrocyte galactitol accumulation at 3, 5 and 24 h post-dose from 5.53 +/- 2.41, 5.43 +/- 1.89, and 5.42 +/- 1.96 mg l-1 2-h-1 to 1.47 +/- 0.30, 1.76 +/- 0.41, and 4.12 +/- 0.72 mg l-1 2-h-1 respectively, p less than 0.01. Galactitol accumulation rate appeared to be a less variable parameter than erythrocyte sorbitol and was not influenced by fluctuations in blood glucose.(ABSTRACT TRUNCATED AT 250 WORDS)

Resistance to ischaemic conduction failure in chronic hypoxaemia and diabetes

Median nerve function was studied in twelve diabetic subjects, six subjects with chronic hypoxaemia and ten control subjects. Resistance to ischaemic conduction failure (RICF), a characteristic electrophysiological feature of diabetic neuropathy, was assessed by measuring the decline in median nerve action potential amplitude at minute intervals for up to 20 minutes while the arm was rendered ischaemic. Initial nerve conduction velocity and action potential amplitude was similar in all three groups. Following the onset of ischaemia the time to a 50% reduction in action potential amplitude was prolonged in both diabetic subjects and hypoxaemic subjects compared with controls. After 20 minutes of ischaemia no control subject had persisting nerve function, while function remained in 5 (80%) of hypoxaemic subjects and 10 (83%) of diabetic subjects. The time to a 50% reduction in action potential amplitude during ischaemia correlated with the blood oxygen saturation among the hypoxic subjects and haemoglobin Alc among diabetic subjects. These results are consistent with the hypothesis that hypoxia has a role in the pathogenesis of resistance to ischaemic conduction failure in diabetes.

Decreased insulin sensitivity and muscle enzyme activity in elderly subjects

Skeletal muscle glycogen deposition, and the activation of muscle glycogen synthase and pyruvate dehydrogenase during a hyerinsulinaemic euglycaemic clamp have been measured in six young and six elderly males matched for body mass index, physical activity and diet. Clamp glucose requirement (insulin, 0.1 U kg-1 h-1) was significantly lower in the older subjects (8.0 +/- 0.4 mg kg-1 min-1) than in younger subjects (10.5 +/- 0.6 mg kg-1 min-1, P less than 0.02). Although the older subjects had a 6.5% decrease in lean body mass, clamp glucose requirement expressed per unit of lean body mass was also significantly decreased in the older subjects (10.2 +/- 0.5 vs. 12.4 +/- 0.6 mg kg-1 min-1, P less than 0.05). The increase in muscle glycogen with the clamp was decreased by 33% in the older subjects (elderly: 13.1 +/- 1.3 mg g-1 protein, young: 19.6 +/- 2.2 mg g-1 protein; P less than 0.05), and was strongly correlated with clamp glucose requirement (r = 0.72, P less than 0.01). Glucose-6-phosphate independent glycogen synthase activity increased significantly between fasting and the end of the clamps in both groups (P less than 0.001), but was lower at the end of the clamp in the older subjects (P less than 0.05). Glycogen synthase activity at the end of the clamp correlated with both clamp glucose requirement (r = 0.83, P less than 0.01) and muscle glycogen deposition (r = 0.73, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Glycated haemoglobins

The association between elevated levels of glycated haemoglobins and diabetes mellitus has been known for twenty years [92]. Since then the determination of glycated haemoglobins has become a valuable tool for the objective assessment of long-term glycaemia in diabetic patients. The marked clinical interest in reliable measurements of glycated haemoglobins has stimulated the development and perfection of the necessary methodology. Limitations of the techniques have led to investigation of the underlying causes. Some of them led to the recognition of processes that were not known to occur in vivo before, such as glycation at sites other than the amino terminus of the beta-chains, modification of haemoglobin by reactants other than glucose or the existence of labile haemoglobin adducts. With ideal methodology these features would have gone unnoticed. Furthermore, the determination of glycated haemoglobin in large populations of diabetic patients has lead to the discovery of new, clinically silent mutant haemoglobins. Today, the routine determination of glycated haemoglobins in diabetic patients probably represents the broadest screening for mutant haemoglobins. The experience with glycated haemoglobins shows that overcoming difficulties in their determination, and progress in biomedical research, are closely intertwined.

Glycated haemoglobin and glycated protein and glucose concentrations in necropsy blood samples

Glycated haemoglobin and glycated protein (fructosamine) and blood glucose concentrations were measured in blood samples collected from 75 patients at necropsy. Estimation of blood glucose was a poor indicator of glycaemia before death. Measurement of glycated haemoglobin by affinity chromatography distinguished non-diabetic patients from diabetic patients. The distinction was not as clear cut when HbA1 was estimated using electroendosmosis. Seven patients, who at necropsy had no known history of diabetes, had glycated haemoglobin concentrations in the diabetic range. Two of these patients were found to be diabetic, and diabetes had been suspected at some time in another three patients. It is concluded that measurement of glycated haemoglobin or HbA1, in necropsy specimens is a valuable tool for assessing glycaemic control in known diabetic patients, and may be useful in diagnosing previously unsuspected diabetes.

Tubular dysfunction and microalbuminuria in insulin dependent diabetes

The nature of microproteinuria in the early years of insulin-dependent diabetes was investigated in a cross sectional study of 80 children with insulin-dependent diabetes and 40 normal children. Urinary excretion of three low molecular weight proteins: alpha-1-microglobulin, beta-2-microglobulin and kappa light chains was used as an index of proximal renal tubular function. The first urine samples of the morning were collected and excretion of proteins measured was expressed as ratio of protein to creatinine. There was a strong correlation between excretion of alpha-1-microglobulin and chi light chains and their excretion was significantly higher in diabetic children indicating decreased proximal tubular reabsorbtion. The excretion of beta-2-microglobulin was found to be an unsatisfactory index of proximal tubular function. Urinary albumin excretion was not significantly raised in diabetic children and did not correlate with urinary alpha-1-microglobulin or chi light chain excretion. Glycaemic control might influence proximal tubular function as both urinary glucose concentration and glycosylated haemoglobin showed correlations with urinary alpha-1-microglobulin excretion and with urinary chi light chain excretion.

The relationship between peripheral nerve resistance to ischaemia and diabetic control

The cause of the abnormal resistance to ischaemia of peripheral nerve function in diabetes is unknown. Median nerve function was more resistant to ischaemia in diabetic patients than in control subjects. In diabetic patients the degree of resistance to ischaemia correlated closely with HbAlc but not with the coincident blood glucose level, the duration of diabetes, the vibration perception threshold at the thumb or the initial median nerve action potential amplitude. Thus in diabetes the resistance of peripheral nerve function to ischaemia is dependent on medium term metabolic control and is not directly related to the presence or absence of neuropathy.

Effect of high dose inhaled beclomethasone dipropionate on carbohydrate and lipid metabolism in normal subjects

The metabolic effects of four weeks' high dose inhaled beclomethasone dipropionate (500 micrograms twice daily) were studied in nine normal subjects with an open study design. No effect was found on fasting blood glucose concentration or glycosylated haemoglobin concentration. Peak blood glucose concentration 30 minutes after a 75 g oral glucose load was, however, significantly higher (7.1 (SEM 0.2) versus 6.7 (0.1) mmol/l, or 128 (3.6) v 121 (1.8) mg/100 ml). After treatment there was a 36% increase in fasting serum insulin concentration (7.6 (0.7) versus 5.6 (0.5) mU/l) and a 32% increase in the area under the serum insulin concentration curve after glucose challenge. High dose inhaled beclomethasone dipropionate treatment raised the fasting plasma cholesterol concentration (4.62 (0.25) v 4.16 (0.26) mmol/l, or 178 (9.7) v 161 (10.0) mg/100 ml) and high density lipoprotein cholesterol (1.19 (0.065) versus 0.97 (0.065) mmol/l, or 45 (2.5) v 37 (2.5) mg/100 ml). Fasting blood lactate and pyruvate concentrations were also significantly higher and blood glycerol lower. The findings indicate that high dose inhaled beclomethasone dipropionate may disturb both carbohydrate and lipid metabolism.

Cysteine adducts of human haemoglobin measured by isoelectric focusing in polyacrylamide gels with a non-linear pH gradient

The in vitro formation of adducts from human haemoglobin formed by alkylation with methyl-methanesulphonate, dimethyl sulphate and iodoacetamide was determined with isoelectric focusing in ultra-thin polyacrylamide gels with a non-linear pH gradient. The most important adduct seen in the gels was identified as HbA alkylated at the beta-93 cysteine. Influences of the chemical nature of the alkylating agents and of the biological environment are discussed. The method is suggested to be applicable to monitoring the biological effects of low, long-term exposure to mixtures of alkylating agents or of exposure to unknown compounds.

Glycated haemoglobin analyses--assessment of within- and between-laboratory performance in a large UK region

The performance of glycated haemoglobin methods has been assessed in 20 laboratories. The methods used in these laboratories were affinity chromatography, electroendosmosis and ion-exchange chromatography. Assessment was based on the results returned by the participating laboratories on distributed specimens. Each method displayed acceptable precision and good linearity. Overall there were substantial differences in results reported by different laboratories, though within each method group these differences were less marked.

Haemoglobin A1c levels in normal and diabetic pregnancies

Serial measurements of the HbA1c levels were performed during pregnancy in 4 groups of patients attending Antenatal Clinics: 36 normal pregnancies; 16 pregnancies in established insulin-dependent diabetic patients; 9 patients with gestational diabetes diagnosed during that pregnancy; and 21 patients who had been diagnosed as having gestational diabetes in at least one previous pregnancy. In the normal pregnancy HbA1c levels showed a small but significant increase from the end of the first trimester to delivery despite blood glucose levels remaining constant throughout. In the insulin-dependent and gestational diabetic patients, blood glucose levels remained significantly higher than in the normal throughout pregnancy but only in insulin-dependent diabetic patients and the newly diagnosed untreated gestational diabetic patients were the HbA1c levels significantly higher than in the normal. In those patients who had previous pregnancies complicated by gestational diabetes, blood glucose levels were significantly higher than in the normal but HbA1c levels were not. This dissociation between blood glucose and HbA1c levels in gestational diabetic pregnancies in particular limits the value of HbA1c levels in monitoring antidiabetic treatment in such pregnancies.

Short-term effect of a 75 g oral glucose load on glycohaemoglobin levels

Two hundred and twenty-three subjects out of a total of 347 with various degrees of glucose tolerance were recalled after a screening survey for diabetes. They were a randomly selected sample of people over the age of 40 and they underwent a formal 75 g glucose tolerance test in order to assess the effect of a glucose load on glycohaemoglobin levels measured by four different assay methods. Oral glucose loading was found to affect glycohaemoglobin levels only when these were measured by an agar-gel electrophoretic method that did not remove the labile aldimine-linked Schiff base fraction. The increase in glycohaemoglobin during the glucose tolerance test as estimated by this method was proportional to the 2 h blood glucose level. Glycohaemoglobin levels measured by agar-gel electrophoresis with elimination of the Schiff base, by affinity chromatography and by iso-electric focussing, were not affected by a 75 g oral glucose load. We conclude that blood samples for glycohaemoglobin assay may be collected at any time of the day, without regard to the subject's previous food intake, provided an assay method is used that removed the aldimine-linked labile fraction.

A comparison of premixed with patient-mixed insulins

Blood glucose control in 12 C-peptide negative patients has been compared in a crossover trial of four insulin treatment regimens: porcine soluble and isophane, premixed porcine soluble/isophane, porcine soluble and lente, all taken twice daily, and once daily bovine ultralente with three porcine soluble injections before meals. Each regimen lasted 8 weeks and included home blood glucose monitoring, telephoned advice on dose adjustment during the first 2 weeks, and home collection of seven-point capillary blood profiles for laboratory analysis. No significant differences between the regimens could be demonstrated when HbA1c, 24 h mean blood glucose, and M-values were evaluated. The average range of blood glucose values for four capillary samples taken at the same time point on different days was 8.0 mmol/l, compared with a maximum difference between regimens of 3.6 mmol/l at any time point, suggesting that blood glucose control is more heavily influenced by erratic insulin absorption than by the insulin regimen chosen. Premixed insulins offer convenience of use without significant deterioration of blood glucose control.

Glycosylated haemoglobin: measurement and clinical use

The discovery, biochemistry, laboratory determination, and clinical application of glycosylated haemoglobins are reviewed. Sources of error are discussed in detail. No single assay method is suitable for all purposes, and in the foreseeable future generally acceptable standards and reference ranges are unlikely to be agreed. Each laboratory must establish its own. Nevertheless, the development of glycosylated haemoglobin assays is an important advance. They offer the best available means of assessing diabetic control.

Recent advances in glycosylated hemoglobin measurements

Glycosylated hemoglobins have gained wide acceptance as an accurate index of long-term blood glucose control in diabetes mellitus. A variety of glycosylated hemoglobin assays is available. There is a high degree of correlation between results determined by these assays. The ideal laboratory method for measuring glycosylated hemoglobin in the diabetic should be accurate, precise, easily standardized, inexpensive, and rapidly performed. Unfortunately, none of the currently used methods meet all of the criteria necessary to be considered the ideal laboratory method. The most widely used methods for quantitating glycosylated hemoglobins--including ion exchange chromatography, electrophoresis, isoelectric focusing, thiobarbituric acid colorimetry, and affinity chromatography--are reviewed with respect to the important advantages and disadvantages of each method for the clinical laboratory. Techniques for quantitating glycosylated proteins other than hemoglobins, such as albumin, are also discussed.