Performance evaluation of a self-administered home oral glucose tolerance test kit in a controlled clinical research setting

AIM

To evaluate the performance of the current, pre-production version of a novel home oral glucose tolerance test (Home OGTT) device when administered by trained research nurses, compared with a reference laboratory glucose analyser and a second laboratory analyser, incorporating a sample processing delay to simulate normal practice.

METHODS

One hundred women (aged 19-48 years), with and without known glucose intolerance were recruited. Following an overnight fast, participants attended for a 75-g OGTT. A fasting capillary sample was applied to the Home OGTT device with a corresponding venous sample collected and measured immediately on the reference YSI 2300 stat plus analyser, and following a 1-h delay on the Randox Daytona Plus analyser. The sampling process was repeated 2 h after the oral glucose load.

RESULTS

Some 97% of tested devices gave complete data for analysis. Good agreement was observed between the reference glucose analyser and the Home OGTT device, with the Home OGTT device displaying a small negative bias (-0.18 mmol/l, -1.75 to 1.39 mmol/mol; -1.0%, -26.4% to 24.5%; absolute and relative mean, 95% limits of agreement). When classified as normal glucose tolerant or glucose intolerant, the Home OGTT device showed 100% and 90% sensitivity, and 99% and 99% specificity using fasting plasma glucose and 2-h glucose respectively. Similar sensitivity (100% and 100%) and specificity (96% and 99%) for fasting plasma glucose and 2-h glucose were observed using the secondary analyser.

CONCLUSIONS

The novel Home OGTT device was reliable and easy to use and showed excellent agreement with two separate laboratory analysers. The Home OGTT offers potential as an effective alternative for clinic-based OGTT testing.

Long-term blood glucose monitoring with implanted telemetry device in conscious and stress-free cynomolgus monkeys

AIMS

Continuous blood glucose monitoring, especially long-term and remote, in diabetic patients or research is very challenging. Nonhuman primate (NHP) is an excellent model for metabolic research, because NHPs can naturally develop Type 2 diabetes mellitus (T2DM) similarly to humans. This study was to investigate blood glucose changes in conscious, moving-free cynomolgus monkeys (Macaca fascicularis) during circadian, meal, stress and drug exposure.

MATERIALS AND METHODS

Blood glucose, body temperature and physical activities were continuously and simultaneously recorded by implanted HD-XG telemetry device for up to 10 weeks.

RESULTS AND DISCUSSION

Blood glucose circadian changes in normoglycemic monkeys significantly differed from that in diabetic animals. Postprandial glucose increase was more obvious after afternoon feeding. Moving a monkey from its housing cage to monkey chair increased blood glucose by 30% in both normoglycemic and diabetic monkeys. Such increase in blood glucose declined to the pre-procedure level in 30 min in normoglycemic animals and >2 h in diabetic monkeys. Oral gavage procedure alone caused hyperglycemia in both normoglycemic and diabetic monkeys. Intravenous injection with the stress hormones, angiotensin II (2 μg/kg) or norepinephrine (0.4 μg/kg), also increased blood glucose level by 30%. The glucose levels measured by the telemetry system correlated significantly well with glucometer readings during glucose tolerance tests (ivGTT or oGTT), insulin tolerance test (ITT), graded glucose infusion (GGI) and clamp.

CONCLUSION

Our data demonstrate that the real-time telemetry method is reliable for monitoring blood glucose remotely and continuously in conscious, stress-free, and moving-free NHPs with the advantages highly valuable to diabetes research and drug discovery.

[Accuracy of a continuous glucose monitoring system in detection of blood glucose during oral glucose tolerance test]

OBJECTIVE

To evaluate the accuracy of continuous glucose monitoring system (CGMS) during oral glucose tolerance test (OGTT) in the detection of blood glucose changes in glucose stress condition.

METHODS

Forty-nine out-patients with fasting plasma glucose of 3.9-11.0 mmol/L underwent continuous blood glucose monitoring using CGMS for 3 days, and OGTT was conducted on the third day. The venous blood glucose was measured at 0, 30, 60, 90, and 120 min after oral glucose intake, and the accuracy of CGMS during OGTT was evaluated.

RESULTS

The correlation indices between CGMS values and the venous blood glucose values during the entire OGTT and in phases of stable, rapidly rising and falling glucose levels were 0.928, 0.901, 0.924 and 0.902, respectively (P<0.001). Clarke error-grid analysis showed that more than 95% of the measured results fell into the A and B zones.

CONCLUSION

CGMS values show good consistency with venous blood glucose values measured during OGTT. CGMS is accurate in detection of rapidly changing blood glucose during OGTT.

A new non-invasive technology to screen for dysglycaemia including diabetes

OBJECTIVE

Assess the ability of a new device based on electrochemical principles using iontophoresis (the EZSCAN) to detect impaired glucose tolerance (IGT) and type 2 diabetes mellitus (DM).

METHODS

Eligible Asian Indian subjects, n=212, had anthropometric and blood pressure measurements, followed by an OGTT, HbA1c, serum lipids tests and EZSCAN measurement.

RESULTS

Biochemically, 24 subjects were diagnosed with DM, 30 with IGT, 57 subjects had normal glucose tolerance (NGT) with metabolic syndrome (MS) and 101 had NGT without MS. Fasting plasma glucose (FPG) and HbA1c levels were highest in the DM group (p<0.0001 for both). HDL-C levels were different (p=0.015). FPG at a cut-off level of 7.0 mmol/L had a low sensitivity to detect DM (29%) EZSCAN had a 75% sensitivity to detect DM, 70% for IGT and 84% for NGT with MS at threshold >50%.

CONCLUSIONS

FPG had low sensitivity to detect DM in the study group. EZSCAN demonstrated good sensitivity to detect IGT and DM and also identified NGT with MS. The concept of measuring ion fluxes through the skin appears to be a powerful method for early detection of MS, IGT and DM.

AKA-Glucose: a program for kinetic and epidemiological analysis of frequently sampled intravenous glucose tolerance test data using database technology

BACKGROUND

The Bergman Minimal Model enables estimation of two key indices of glucose/ insulin dynamics: glucose effectiveness and insulin sensitivity.

METHODS AND RESULTS

In this paper we describe AKA-Glucose, a program that combines MINMOD Millennium (minimal model analysis software) with relational database technologies. AKA-Glucose enables the fitting of individual frequently sampled intravenous glucose tolerance test (FSIGT) data sets to the Minimal Model and the secure storage in a dedicated database (and retrieval from) of thousands of individual subjects' demographic data, their individual FSIGT data, and each subject's parameters and indices derived from minimal model analysis. AKA-Glucose also enables the population analysis of various strata or subpopulations within the database. AKA-Glucose has all of the capabilities of MINMOD Millennium, provides Minimal Model parameter estimates that are concordant with estimates from previous MINMOD software, and allows importation of data files from earlier versions of the MINMOD software.

CONCLUSIONS

By combining FSIGT data fitting, population analysis, and relational database technologies, AKA-Glucose is the first minimal model software designed specifically for researchers confronted with minimal model and epidemiological analysis of large numbers of either human or animal FSIGT data sets.

Challenges of implementing Point-of-Care Testing (POCT) glucose meters in a pediatric acute care setting

OBJECTIVES

To investigate factors contributing to analytical bias in POCT glucose values generated by the NICU versus the core laboratory.

METHODS

The LifeScan Flexx hospital system glucose meters (SureStep) were used in precision and comparison studies between the NICU and laboratory (ABL715 and Vitros 950).

RESULTS

Analysis of 40 neonatal blood samples revealed a positive bias between the NICU glucose meters versus either the laboratory glucose meter or instrument (mean difference of 0.28 and 0.21 mmol/L, respectively). Linear regression analysis (R2 = 0.0584) of the difference in glucose results versus time elapsed between measurements indicated that the bias observed between the NICU and laboratory glucose meters was not due to in vitro glycolysis for samples transported on ice. Further analysis indicated that the bias appeared to be mostly operator driven, with different NICU operators exhibiting different mean biases. Increasing the amount of blood applied to the SureStep Pro test strip (e.g., 60 vs. 20 microL), led to higher values for glucose concentration for the same blood. Nearly 50% of all glucose values reported for the NICU were obtained by the SureStep Flexx glucose meters in a 3-month period following the introduction of POCT, yet the number of laboratory-reported glucose results for the same period increased by 21% as compared to the previous year.

CONCLUSIONS

Operator error appears to be a source of bias present between the NICU and laboratory, and despite glucose meter utilization in the NICU, the number of glucose measurements by the central laboratory increased after POCT introduction.

Noninvasive glucose measurement by monitoring of scattering coefficient during oral glucose tolerance tests. Non-Invasive Task Force

BACKGROUND

Continuous glucose monitoring by means of optical glucose sensors would allow patients with diabetes to check their metabolic control to their convenience. In an earlier study, we showed that noninvasive glucose monitoring is feasible for rapid changes in blood glucose by means of measuring the scattering coefficient of human skin. In this study, we investigated whether also slower changes in blood glucose, this time induced by an oral glucose load, can also be monitored by this approach.

METHODS

Five healthy subjects and 13 patients with type 2 diabetes have been given a 75-g oral glucose load. Portable noninvasive systems were used to measure the skin tissue scattering coefficient. For this purpose, two optical sensor heads were attached directly to the skin of each volunteer. Light was applied to the skin and the reflected light intensity was registered.

RESULTS

In 8 of 10 measurements, correlation of changes in scattering coefficient with changes in glycemia was acceptable. In 19 of 26 measurements (73%) of patients with type 2 diabetes the observed changes in the scattering coefficient also correlated in acceptable manner. The accordance between the simultaneous measurements of the two sensor heads was acceptable in 13 of 18 volunteers and patients studied. There were virtually no differences in the quality of the measurements between healthy volunteers and patients with diabetes.

CONCLUSIONS

This study shows that also slow changes in blood glucose induced by an oral glucose load can be monitored by registration of scattering coefficient changes. It remains to be elucidated why this has not been possible in all experiments.

Evaluation of a simplified intravenous glucose tolerance test and a reflectance glucose meter for use in cats

A simplified intravenous glucose tolerance test has been developed for use in domestic cats and the results compared with those obtained using the standard test. The simplified test used two cephalic catheters, implanted in unsedated, unanaesthetised cats three hours before the test. Blood samples were collected before and after intravenous administration of glucose (0.5 g/kg bodyweight). Blood glucose concentration was measured with a reflectance glucose meter and an automated chemistry analyser. There were no significant differences between the results derived from the two tests. Because the simplified glucose tolerance test is easier to perform, requires no anaesthesia, uses only cephalic catheters and can be done on an outpatient basis, it is more cost effective and more clinically applicable. There were no significant differences between the results of glucose measurements with the two machines and the simplified glucose tolerance test can therefore be carried out with the reflectance glucose meter.

Predictive value of HemoCue capillary whole blood glucose measurements in pregnancy

OBJECTIVE

We determined the ability of capillary whole blood glucose concentrations to predict venous plasma and whole blood glucose levels.

METHODS

During a standard oral glucose tolerance test in 29 pregnant women, paired capillary and venous blood samples were collected for analysis of glucose concentrations by the HemoCue photometer and by central laboratory methods.

RESULTS

Glucose concentrations determined serially in a single blood sample by the HemoCue method were highly reproducible, with a coefficient of variation of 2.3%. However, glucose levels in blood from two different fingersticks from the same patient varied on average by 3 mg/dL, with a maximum difference of 14 mg/dL. Although capillary whole blood glucose results obtained by the HemoCue method correlated well with venous plasma or whole blood glucose measurements (r = 0.98 and r = 0.97, respectively) over the range investigated (60-250 mg/dL), individual capillary whole blood glucose measurements were only a fair predictor of venous values, with 95% of measured venous levels within +/- 26 mg/dL and +/- 20 mg/dL for concentrations predicted for plasma and whole blood, respectively.

CONCLUSION

Sampling factors rather than measurement accuracy limit the ability of capillary whole blood glucose measurements to predict venous concentrations.

[A rapid method for diabetes screening in pregnancy]

Gestational diabetes affects about 3% of pregnancies in German-speaking countries. Roughly one third of these pregnancies develop a requirement of insulin. In unrecognised and hence untreated pregnancies, perinatal morbidity and mortality are increased 20-fold. Gestational diabetes is asymptomatic and only 60% of patients have risk factors for the condition; thus, general screening with oral glucose tolerance testing is necessary to detect all cases. Most antenatal medical care is provided by gynaecologists in practice and by general practitioners who do not have a sophisticated laboratory at their immediate disposal. General screening requires a test that is simple, inexpensive and quick but nonetheless meets high quality standards. A new microcuvette rapid test fulfills these requirements; the results are ready within a few minutes' time. We performed parallel blood glucose measurements with a standard enzymatic method and with the rapid test in 500 unselected pregnant women undergoing an oral glucose tolerance test at our obstetric clinic. The mean fasting, 1-hr and 2-hr values were 77,128 and 106 mg/dl, respectively, as measured by the enzymatic test and 75,129 and 107 mg/dl as measured by the rapid test. The results of the reference enzymatic method and the rapid test agreed at a high level of significance (r = 0.98; p < 0.0001).

[Use of an automatic blood glucose measurement system for the assessment of insulin resistance during the oral glucose tolerance test]

An automatic glycemic control system (Beta-like, Esaote) was used to calculate the insulin area (IA) required to keep glycemia within the normal range during OGTT (using NDDG criteria). IA was calculated by adding total endogenous insulin to insulin infused by the Betalike system (Actrapid HM, Novo). During the test, glycemia was obliged to follow a mean normal curve using an insulin infusion according to a special algorithm which automatically adapted to individual parameter variations during the different stages of OGTT. Fourteen blood samples were collected to assay metabolites (glucose, NEFA, lactate and alanine) and hormones (insulin, C peptide, glucagon). Data on insulinemia and glycemia were used to calculate the respective areas under the total and incremental curve (IA expressed in UL-1 min-1 and GA expressed in mM.L-1.min-1); an insulin resistance index was then calculated (total and incremental) using the following formula: IA/(normal GA/patient GA). This test allows us: a) to evaluate the insulin secretory response to a standard glycemic stimulus represented by a glycemic curve within the normal range; b) to calculate the quantity of insulin necessary to maintain the glycemic curve within the normal range; c) to evaluate the body's total insulin resistance according to an index calculated on the basis of the insulin area required; d) to compare the calculated insulin resistance index with NEFA and glucagon data obtained during the test; e) to identify the exact evolution of these events over time during OGTT.

Oral glucose tolerance test--can the reflectance meter replace laboratory-based methods?

Sixteen national servicemen detected to have glycosuria on routine medical examination were subjected to 3 successive oral glucose tolerance tests. Capillary blood glucose was measured by reflectance meter in the first test (oGTT1), venous whole blood glucose by Beckman Synchron CX3 Analyser in the second (oGTT2) and by both methods in the third (oGTT3). In oGTT1, 1 subject was classified as diabetic and 15 as Impaired Glucose Tolerance (IGT). In oGTT3, using capillary blood glucose, 1 was diabetic, 8 IGT and 7 normal. Using venous whole blood, in oGTT2, 1 was diabetic, 3 IGT and 12 normal as compared to 1 diabetic, 4 IGT and 11 normal in oGTT3. There is considerable variation in classification as a result of using capillary blood glucose measured by reflectance meter as compared to the laboratory-based method. Capillary blood glucose measurement for oral glucose tolerance test cannot be recommended.

Serum fructosamine concentrations in Singapore pregnant women

Serum fructosamine levels in women at pregnancy (28 weeks' gestation) were determined. The women (n = 99) also participated in an oral glucose tolerance test (OGTT) with a 75g liquid glucose load, to determine their glucose tolerance. At 32 weeks' gestation, seventy-nine of them repeated the oral glucose tolerance test and fructosamine measurement. Results showed that fructosamine levels in pregnant women with normal glucose tolerance (2.20 +/- 0.19 mmol/l, n = 76), were not statistically different from those with glucose intolerance (gestational diabetes: 2.19 +/- 0.22 mmol/l, n = 23) at 28 weeks' and also 32 weeks' gestation. However, serum fructosamine levels in pregnant women were lower than those in non-pregnant subjects. Serum fructosamine measurement is not a sufficiently sensitive test for diagnosis of gestational diabetes.

Medical diagnostic technology in the home

This article studies the issues surrounding the assessment of several home diagnostic tests. First, the authors review the current data and proper use of fecal occult blood and pregnancy tests. Second, they evaluate the roles of blood and urine glucose monitoring in the management of diabetes mellitus and home pressure monitoring in the management of hypertension. The authors conclude that while home measurement of blood pressure or blood sugar can be recommended to improve compliance with medical programs, home fecal occult blood testing, while helpful, has not been fully investigated.

Diagnosis of gestational diabetes by capillary blood samples and a portable reflectance meter: derivation of threshold values and prospective validation

Paired capillary-venous samples were obtained from 255 women undergoing a glucose challenge test and 116 women undergoing an oral glucose tolerance test. The capillary equivalents for the venous threshold values were calculated by regression analysis. The glucose challenge test predictions of either normal or abnormal agreed in 82%. The sensitivity, specificity, and positive and negative predictive values for the capillary oral glucose tolerance test were 89%, 90%, 62%, and 98%, respectively. These capillary equivalents were then applied prospectively to 147 women undergoing a glucose challenge test and 141 women undergoing an oral glucose tolerance test. The concurrence rate of the glucose challenge test in the prospective group was 90%. The sensitivity, specificity, and positive and negative predictive values for the capillary oral glucose tolerance test were 64%, 95%, 75%, and 92%. When the venous threshold recommendations of the American Diabetes Association were used instead of those standard at our institution, these values increased to 75%, 98%, 83%, and 96%, respectively. The recommended capillary values of the American Diabetes Association were 100% sensitive but had a positive predictive value of only 20%. Based on the prospective group, the cost per case of gestational diabetes identified would decline 63% if both a capillary glucose challenge test and an oral glucose tolerance test were used and 25% if the capillary glucose challenge test and venous oral glucose tolerance test were used. Combining the data set for new regression equations, the following venous-capillary threshold sets emerged: glucose challenge test, 140 mg/dl/150 mg/dl; fasting oral glucose tolerance test, 105 mg/dl/114 mg/dl; 1 hour, 190 mg/dl/211 mg/dl; 2 hours, 165 mg/dl/183 mg/dl; 3 hours, 145 mg/dl/157 mg/dl. The sensitivity, specificity, and negative predictive values for the capillary oral glucose tolerance test with these thresholds were 80%, 97%, 80%, and 97%. In conclusion, capillary glucose testing for diabetes during pregnancy is feasible and cost-effective.

Capillary blood sugar values in infants and children during oral glucose tolerance tests

A capillary blood micro technic for blood sugar utilizing the Unopette, a device forobtaining the required specimens, is described. The accuracy of the Unopette was tested and established.

Three-hour capillary blood oral glucose tolerance tests, using this methodology, were performed on a total of 159 children in three age groups; one week to one-and-one-half years, one-and-one-half to three years, and three to twelve years. Oral glucose solution was administered according to age and weight. All children had negative family histories for diabetes and were in good health. The mean blood sugar values for each of the three age groups were compared with one another for each of the sampling periods. No significant differences at the 5 per cent level were observed among the group means at any of the six testing periods. Over-all means and the values of ± 2 standard deviations and the third to ninety-seventh percentiles were determined for the three age groups combined. Values for the :± 2 standard deviation range were: Fasting (55 to 88 mg./ 100 ml.); thirty minutes (77 to 160 mg./100 ml.); sixty minutes (66 to 149 mg./100 ml.); ninety minutes (68 to 133 mg./100 ml.); 120 minutes (59 to 130 mg./100 ml.); 180 minutes (46 to 105 mg./100 ml.).