Roger Johnson

Fructosamine: A new approach to the estimation of serum glycosylprotein. An index of diabetic control

The development of a novel manual method designed to measure serum glycosylprotein as an index of diabetic control is described. The method relies on the ability of ketoamines (fructosamines) to act as reducing agents in alkaline solution. Conditions are described for a simple colorimetric procedure which permits assay of both a synthetic fructosamine and purified albumin while severely limiting the contribution of interfering substances. Applied to whole sera, the measurement is linear with volume of serum assayed. It allows clear discrimination of normal and diabetic populations (p less than 0.001), and is significantly correlated with fasting blood glucose concentration (r = 0.72) and with a thiobarbituric acid procedure for measuring glycosylprotein-derived hydroxymethylfurfural (r = 0.58). The method is rapid (at least 12 samples per hour) and demands only simple equipment.

Clinical usefulness of estimation of serum fructosamine concentration as a screening test for diabetes mellitus.

Fructosamine, a putative measure of serum glycosylated proteins, was measured in 74 subjects referred for oral glucose tolerance tests. A normal range (mean (2 SD] of 1.6 (0.4) mmol/l (40(10) mg/100 ml) derive from results obtained in 83 healthy non-diabetic volunteers permitted the detection of 15 out of 17 (88%) subjects with proved diabetes and yielded only five (9%) false positive diagnoses. Fructosamine concentrations correlated significantly (p less than 0.001) with fasting plasma glucose concentrations (r = 0.76) and glycosylated haemoglobin concentrations (r = 0.70). A longitudinal study suggested that fructosamine concentration was an index of intermediate term (one to three weeks) blood glucose control. Fructosamine concentration was not related to uraemia and did not depend on albumin or total protein concentrations, provided that serum albumin concentrations remained above 30 g/l. Estimation of fructosamine concentrations is a fully automated procedure and may provide a simple means of screening for diabetes mellitus.

Serum fructosamine concentration as measure of blood glucose control in type I (insulin dependent) diabetes mellitus.

Serum fructosamine activity was studied in 42 patients with type I (insulin dependent) diabetes mellitus and 30 non-diabetic volunteers as an index of blood glucose control. There was a significant correlation both between fructosamine and glycosylated haemoglobin values (r = 0.82) and between fructosamine and the fasting C peptide concentration (r = -0.81). Test results in 14 of the diabetics reflected the mean plasma glucose concentration calculated from 25 serial estimations in a single 24 hour period (r = 0.75; p less than 0.01) but not the mean amplitude of glycaemic excursion (r = 0.23; p greater than 0.05). Fructosamine concentrations measured in these multiple blood specimens did not change significantly throughout the day (mean coefficient of variation 4.1%) despite wide variability of the respective plasma glucose concentrations (mean coefficient of variation 36.2%). It is concluded that a single random serum sample analysed for fructosamine concentration provides a simple and reliable assessment of glucose homoeostasis in patients with type I diabetes mellitus.

Serum fructosamine concentrations in patients with type II (non-insulin-dependent) diabetes mellitus during changes in management

The serum fructosamine concentration was examined as a new means to monitor metabolic control in non-insulin-dependent diabetes during changes in management. Weekly fructosamine estimations were compared with glycosylated haemoglobin (HbA1c), 24 hour urinary glucose, and fasting plasma glucose concentrations in a 17 week study entailing withdrawal and reinstitution of oral treatment. The serum fructosamine concentration was more sensitive than the other measurements in detecting a deterioration in diabetic control after stopping oral hypoglycaemic drugs. The response to reinstitution of treatment was not significant in the first three weeks (p = 0.266), despite a highly significant reduction in fasting plasma glucose (p = 0.001) and 24 hour urinary glucose concentrations (p = 0.012). Compared with HbA1c, concentrations of fructosamine appeared more useful in monitoring short term (three to six weeks) changes after alterations in management of diabetes. Additional advantages were lower cost and technical simplicity of measurement.

Accuracy of devices used for self-monitoring of blood glucose

We measured the inaccuracy of 17 home blood glucose monitors (two visually read, eight colorimetric and seven amperometric). Using strips from a single batch, blood glucose measurements were performed by three medical laboratory technologists on at least 50 capillary blood specimens from patients attending two diabetes clinics. Additional capillary blood was deproteinized and assayed with hexokinase to give a whole blood glucose result. A dedicated glucose analyser was also studied to cross-validate the methodology. At a mean glucose concentration of about 9 mmol/L, monitor readings differed from the reference results by −5.1 to + 19.5% with three systems failing to meet the American Diabetes Association guideline for total error of less than 15%. This problem would be alleviated by manufacturers adopting a common policy on calibration and on reporting as a plasma or whole blood value.

Analytical error of home glucose monitors: a comparison of 18 systems.

In a quality review of 18 home blood glucose monitors, we measured the imprecision and incidence of significant error of 12 colorimetric and six amperometric systems by using capillary blood specimens from patients attending diabetes clinics. Imprecision at the mean glucose concentration found in the respective blood specimens (about 9 mmol/L) gave coefficients of variation (CV) ranging from 5·2 to 22·8%. Eight monitors including five of amperometric design had a CV of less than 10%. The incidence of significant error (defined as the proportion of specimens differing in value by more than 15% from a reference hexokinase assay of glucose in capillary blood) varied from 6 to 76%. Among the eight monitors identified as being most precise, the majority produced results that differed markedly from the reference assay, underlining the need for a common approach to calibration of home glucose monitors.

Relationship between albumin and fructosamine concentration in diabetic and non-diabetic sera

We investigated the contribution of albumin to serum fructosamine activity. On gel exclusion chromatography, pooled diabetic and pooled non-diabetic sera before and after incubation with [14C]glucose differed in fructosamine activity and radioactivity mainly in the albumin-containing fractions. We confirmed the major contribution of glycated albumin to serum fructosamine concentration using affinity chromatography on Blue Sepharose. The importance of high molecular mass species was further demonstrated by the recovery of reducing activity following dialysis and charcoal treatment. Fructosamine measurements in diabetic patients were not correlated with serum albumin concentration in individuals with urinary albumin less than 1 g/l. We conclude that fructosamine activity is a convenient measure of glycosylprotein concentration and that the index responds mainly to glycation of albumin. However, routine correction for serum albumin concentration is inappropriate.

Significance of variation in turnover of glycated albumin on indices of diabetic control

We measured the half-time of disappearance of 125I-labelled glycated albumins in a rat model of diabetes with continuous infusion of physiological saline and insulin. Our results indicate that (i) in non-diabetic rats, continuous infusion of saline per se did not affect the concentrations of glucose or of fructosamine, and the half-time of disappearance of albumin was unaffected by degree of glycation; (ii) hyperglycaemia (mean plasma glucose concentration of 18-27 mmol/l) caused a small but significant increase in half-time of labelled glycated albumin disappearance from a mean of 42 h to a mean of 47 h; (iii) this effect of hyperglycaemia outweighed any effect of increase in albumin excretion detected in poorly controlled diabetic rats without infusion. We conclude that the effect of hyperglycaemia in slowing turnover of glycated albumin is likely to be insignificant in relation to its effect in promoting glycation, and may be species-dependent. However, in nondiabetics, variation of turnover of glycated albumin may well be significant in explaining the wide interindividual variation in concentration of glycated protein.

Where have all the pennies gone ? The work of Manchester medical audit advisory group

Medical audit has its critics, who point to the large sums of NHS cash that seem to be disappearing down a medical plughole. These criticisms are recognised by medical audit advisory groups but there are many reasons why the work of these groups has not yet resulted in many publications in journals or bumped up health indicators. After discussing the criticism this article describes the work of the medical audit advisory group in Manchester. Real changes in cooperative working with general practice teams and between practices are taking place, and improved relationships between general practice and the hospitals are being helped by joint audit work. The Manchester group is also working to help in setting standards and to cooperate with purchasing. The work of the group is changing as it develops.

Harmonization of laboratory testing - A global activity.

The harmonization of laboratory testing is a high priority topic in Laboratory Medicine. It is more than harmonized terminology, units of reporting, methodology and reference intervals but, rather, covers a wide range of topics from the “pre-pre-analytical” phase (‘Right test at the Right time for the Right patient’) to the analytical aspects and reporting of critical results through to consumer education and the meaning of laboratory tests in lay terms (“post-post-analytical” phase). Harmonization should lead to safer andmore accurate interpretation of patient results [1]. Any new concept requires innovative and practical ideas if it is to succeed. This special themed issue of 26 articles explores how we might achieve the closer comparability of processes to achieve closer comparability of laboratory outcomes globally. Experts provide reviews, commentaries and critical opinions about the benefits of harmonization and its future directions. Aarsand and Sandberg [2] suggest practical ways of achieving harmonization of laboratory testing and describe the potential barriers. They recommend close interaction with all stakeholders including the Laboratory Medicine community, diagnostic industry, clinicians, professional societies, IT providers, consumer advocate groups and the government as essential for harmonization projects to be successful and to achieve improved clinical effectiveness of critical tests and greater patient safety. In particular, harmonization initiatives should improve procedures and processes at the laboratory-clinical interface. As Plebani and Panteghini discuss [3], it is essential to promote close relationships between laboratorians and clinicians to improve the laboratory testing process. As a practical example, Berg [4] describes the elements of a global harmonization model based on the United Kingdom harmonization initiative and the importance of marketing communications as an inclusive approach involving key pathology and clinical professional groups. Misra and Barth [5] go on to describe how when being developed guidelines on test selection require an integral interaction between clinicians and laboratory specialists, and that this should help to harmonize practice, reduce inappropriate test selection and reduce treatment variations secondary to analytical variations. Harmonizing the pre-analytical phase requires use of standardized operating procedures for correct test selection, sample collection and handling. However, standardized protocols for patient preparation for laboratory testing are currently lacking. Simundic et al. [6] for the European Federation of Clinical Chemistry and Laboratory Medicine Working Group on the Pre-analytical Phase (EFLM WG EFLM WG-PA) discuss the need to provide a framework for the harmonization of definitions for fasting requirements for laboratory tests. In a more contentious article, Dolci and Panteghini [7] raise the possibility of harmonizing automatic hemolysis index (HI) assessment and, in particular, the need to develop a harmonized response for reporting results of