Evaluation of the analytic performances of the new HPLC system HLC-723 G7 for the measurement of hemoglobin A1c

Personal real-time continuous glucose monitoring in patients 65 years and older

OBJECTIVE

Little information is available on personal real-time continuous glucose monitoring (PCGM) in patients ≥65 years old. We report on PCGM use in insulin-requiring patients ≥65 years old in a community endocrine practice.

METHODS

Patients ≥65 or older who had been prescribed PCGM were identified by retrospective review. Glycated hemoglobin (A1C) values from the year prior and subsequent to PCGM prescription, the most recent A1C value, continued PCGM usage, percentage reporting severe hypoglycemia (SH), and rate of SH were examined.

RESULTS

Thirty-eight patients were identified: 31 with type 1 diabetes, 21 females, mean age 70 years (range 65-78), and a mean diabetes duration of 31 years. Overall, 28 were on insulin pump therapy, 29 were using PCGM regularly, and 25 had both pre- and post-PCGM use A1C results. Regular PCGM use was associated with a decrease in mean (SD) A1C: 7.6 (0.9)% to 7.1 (0.9)%, (P<.0001) that was maintained until the most recent A1C value (7.2 [0.8]%, P = .0145, average 37 months), with fewer reporting SH (from 79% to 31%, P = .0002), and a lower rate of SH (0.37 to 0.12 per year, P = .0007). The group of 9 patients who did not continue PCGM (mean use 3 months) was too small to allow meaningful statistical evaluation. Lack of insurance coverage was the most common reason given for not using/continuing PCGM. Those continuing PCGM were more likely to have insurance coverage for PCGM (86%) than those not continuing PCGM (25%).

CONCLUSIONS

Patients ≥65 with insulin-requiring diabetes achieve improved glycemic control with regular PCGM use. The presence of PCGM insurance coverage favored continued PCGM use.

Hemoglobin A1C, mean glucose, and persistence of glycation ratios in insulin-treated diabetes

OBJECTIVE

Determine the relationship between mean glucose (MG), as assessed by continuous glucose monitoring (CGM), and hemoglobin A1c (A1C) in insulin-requiring adults in a clinical practice setting and examine the persistence of this relationship over time.

METHODS

In this retrospective record review in a diabetes practice, a linear regression model was developed using data sets from all patients with ≥1 available download of a Dexcom SevenPlus CGM device in which there was >50% utilization in the 60 days prior to a laboratory A1C. Persistence of the MG to A1C relationship was examined in patients with ≥2 data sets available.

RESULTS

A total of 139 patients had ≥1 data set available for evaluation, and 101 patients had ≥2 data sets (range, 2 to 6; total, 279). The slope of the MG versus A1C curve was 19.5 mg/dL for each 1% change in A1C, with an intercept of 17.7 mg/dL. Although 88% of the measured MG values were within 15% of the A1C-predicted MG, there was substantial variation in individuals, with differences as large as ±26%. The MG to A1C (MG:A1C) ratio, which is a measure of glycation, was normally distributed, with a median of 21.6. Spearman correlation coefficients for the MG:A1C ratio on repeated measures ranged from 0.52 to 0.73, demonstrating persistence.

CONCLUSION

The relationship between MG and A1C is linear in a population but can vary between individuals. The MG:A1C ratio was normally distributed, tended to persist in individuals over time, and thus could be useful to identify apparent high and low glycators. Glycemic goals may need to be modified in such patients.

GLYCEMIC EFFECTS OF SGLT-2 INHIBITOR CANAGLIFLOZIN IN TYPE 1 DIABETES PATIENTS USING THE DEXCOM G4 PLATINUM CGM

OBJECTIVE

Limited information is available on chronic use of sodium glucose cotransporter 2 inhibitors in type 1 diabetes (T1D). We conducted a retrospective review of T1D patients on Dexcom G4Platinum continuous glucose monitors (DCGMs) >1 year (mean, 4.6 years) who were prescribed canagliflozin (CANA) 100 mg daily and had a baseline DCGM 30-day download prior to and a second download after at least 1 month (mean, 3.7 months) taking CANA 100 mg daily. The glycemic, weight, and systolic blood pressure (SBP) effects are reported.

METHODS

We identified 27 patients meeting the selection criteria: 14 men; 25 white; 22 on pump; average T1D duration, 34 years (range, 12 to 48 years); average hemoglobin A1C (A1C), 7.6% (range, 6.1 to 9.8%); 22 with baseline A1C 7.0% or higher. All patients had an estimated glomerular filtration rate (eGFR) at baseline of 60 mL/min/1.73 m(2) or higher and were normotensive or on stable therapy. On average, 29 days of CGM data was reviewed. Total daily insulin dose (TDD) was available in 21 patients. We identified 27 patients who were judged to be candidates for CANA but did not have any change in glycemic therapy other than insulin adjustment as controls.

RESULTS

CANA resulted in significant reductions in mean blood glucose, CGM standard deviation, time in hyperglycemia, A1C, weight, SBP, and TDD, with increased time in target, with minimal increase in hypoglycemia and no significant change in eGFR. Three females developed genital mycotic infections but continued therapy, 2 developed ketoacidosis from insulin interruption.

CONCLUSION

CANA offers promise as adjunct therapy in T1D, though caution is advised.

High-resolution HbA(1c) separation and hemoglobinopathy detection with capillary electrophoresis

The CAPILLARYS HbA(1c) kit used on the CAPILLARYS 2 Flex Piercing system is designed for separating and quantifying the HbA(1c) fraction of hemoglobin while detecting hemoglobin variants and HbA(2). The aim of this study was to assess the performance of this new capillary electrophoresis kit for routine HbA(1c) quantification for patients with diabetes. The reliability of the system for HbA(2) measurement was also assessed. Precision, correlation, and linearity studies were performed. The effect of hemoglobin concentration and the presence of coexistent interfering substances were evaluated. The results were found to be accurate and linear in the clinically significant analytic range with excellent precision (mean interassay coefficient of variation of 0.7%). HbA(1c) measurement is independent of the presence of common hemoglobin interferences for HbA(1c) quantification and the total concentration of hemoglobin. Moreover, the technique provides a rapid and reliable separation of HbA(2). The measurement is reproducible and the results in β-thalassemia carriers were statistically different from those in noncarriers. Thus, this technique might be used for β-thalassemia detection. Given the short time of the analysis and the high throughput, this is a suitable system for the control of diabetes and the detection of hemoglobinopathies in laboratories with high workflow.

The effect of a supported exercise programme in patients with newly diagnosed Type 2 diabetes: a pilot study

The aim of this study was to examine the effectiveness of either a standard care programme (n = 9) or a 12-week supported exercise programme (n = 10) on glycaemic control, β-cell responsiveness, insulin resistance, and lipid profiles in newly diagnosed Type 2 diabetes patients. The standard care programme consisted of advice to exercise at moderate to high intensity for 30 min five times a week; the supported exercise programme consisted of three 60-min supported plus two unsupported exercise sessions per week. Between-group analyses demonstrated a difference for changes in low-density lipoprotein cholesterol only (standard care programme 0.01 mmol · L(-1), supported exercise programme -0.6 mmol · L(-1); P = 0.04). Following the standard care programme, within-group analyses demonstrated a significant reduction in waist circumference, whereas following the supported exercise programme there were reductions in glycosylated haemoglobin (6.4 vs. 6.0%; P = 0.007), waist circumference (101.4 vs. 97.2 cm; P = 0.021), body mass (91.7 vs. 87.9 kg; P = 0.007), body mass index (30.0 vs. 28.7 kg · m(-2); P = 0.006), total cholesterol (5.3 vs. 4.6 mmol · L(-1); P = 0.046), low-density lipoprotein cholesterol (3.2 vs. 2.6 mmol · L(-1); P = 0.028), fasting β-cell responsiveness (11.5 × 10(-9) vs. 7.0 × 10(-9) pmol · kg(-1) · min(-1); P = 0.009), and insulin resistance (3.0 vs. 2.1; P = 0.049). The supported exercise programme improved glycaemic control through enhanced β-cell function associated with decreased insulin resistance and improved lipid profile. This research highlights the need for research into unsupported and supported exercise programmes to establish more comprehensive lifestyle advice for Type 2 diabetes patients.

A1C to detect diabetes in healthy adults: when should we recheck?

OBJECTIVE

To evaluate the optimal interval for rechecking A1C levels below the diagnostic threshold of 6.5% for healthy adults.

RESEARCH DESIGN AND METHODS

This was a retrospective cohort study. Participants were 16,313 apparently healthy Japanese adults not taking glucose-lowering medications at baseline. Annual A1C measures from 2005 to 2008 at the Center for Preventive Medicine, a community teaching hospital in Japan, estimated cumulative incidence of diabetes.

RESULTS

Mean age (+/-SD) of participants was 49.7 +/- 12.3 years, and 53% were male. Mean A1C at baseline was 5.4 +/- 0.5%. At 3 years, for those with A1C at baseline of <5.0%, 5.0-5.4%, 5.5-5.9%, and 6.0-6.4%, cumulative incidence (95% CI) was 0.05% (0.001-0.3), 0.05% (0.01-0.11), 1.2% (0.9-1.6), and 20% (18-23), respectively.

CONCLUSIONS

In those with an A1C <6.0%, rescreening at intervals shorter than 3 years identifies few individuals (approximately <or=1%) with an A1C >or=6.5%.

A1C underestimates glycemia in HIV infection

OBJECTIVE

The objective of this study was to determine the relationship between A1C and glycemia in HIV infection.

RESEARCH DESIGN AND METHODS

We completed a prospective cross-sectional study of 100 HIV-infected adults with type 2 diabetes (77%) or fasting hyperglycemia (23%) with measured glucose, A1C, mean corpuscular volume (MCV), and fructosamine. A total of 200 HIV-uninfected type 2 diabetic subjects matched for key demographic characteristics served as control subjects.

RESULTS

Relative to the control subjects, A1C underestimated glucose by 29 +/- 4 mg/dl in the HIV-infected subjects. Current nucleoside reverse transcriptase inhibitors (NRTIs), higher MCV and hemoglobin, and lower HIV RNA and haptoglobin were associated with greater A1C-glucose discordance. However, only MCV and current NTRI use, in particular abacavir, remained significant predictors in multivariate analyses. Fructosamine more closely reflected glycemia in the HIV-infected subjects.

CONCLUSIONS

A1C underestimates glycemia in HIV-infected patients and is related to NRTI use. Use of abacavir and increased MCV were key correlates in multivariate analyses. Fructosamine may be more appropriate in this setting.

The silent hemoglobin alpha chain variant Hb Riccarton [alpha51(CE9)Gly-->Ser] may affect HbA1c determination on the HLC-723 G7 analyzer

BACKGROUND

Structural hemoglobin variants can affect the accuracy of hemoglobin A1c (HbA1c) testing and represent the most common pitfall in the determination of HbA1c. We here describe the characterization of an alpha chain variant in diabetic patients as the cause of an abnormal presentation of the HbA1c fraction on the HLC-723 G7 analyzer.

METHODS

HbA1c analysis was performed using various HPLC-based HbA1c analyzers and by immunoassay. alpha-Globin mutation analysis was performed by GAP-PCR and DNA sequencing.

RESULTS

The peak partially overlapping HbA1c in the chromatogram represents the glycated fraction of the silent alpha chain variant Hb Riccarton [alpha51(CE9)Gly-->Ser]. This aberrant peak is uniquely identified by the HLC-723 instrument, as it is not observed on other HPLC-based HbA1c analyzers. Occasionally, the HLC-723 may fail to properly integrate both glycated Hb fractions, resulting in a falsely low HbA1c result. The variant was confirmed in samples from other diabetic patients with identical chromatographic patterns.

CONCLUSIONS

The silent alpha chain variant Hb Riccarton [alpha51(CE9)Gly-->Ser] leads to an abnormal chromatographic presentation on the HLC-723 analyzer with a risk of erroneous HbA1c determination. Manual validation of chromatograms to detect abnormalities caused by Hb variants is important to prevent incorrectly produced HbA1c results from being reported.

The loss of postprandial glycemic control precedes stepwise deterioration of fasting with worsening diabetes

OBJECTIVE

The aim of the study was to determine whether the loss of fasting and postprandial glycemic control occurs in parallel or sequentially in the evolution of type 2 diabetes.

RESEARCH DESIGN AND METHODS

In 130 type 2 diabetic patients, 24-h glucose profiles were obtained using a continuous glucose monitoring system. The individuals with type 2 diabetes were divided into five groups according to A1C levels: 1 (<6.5%, n = 30), 2 (6.5-6.9%, n = 17), 3 (7-7.9%, n = 32), 4 (8-8.9%, n = 25), and 5 (> or =9%, n = 26). The glucose profiles between the groups were compared. The overall glucose concentrations for the diurnal, nocturnal, and morning periods, which represent the postprandial, fasting, and the dawn phenomenon states, respectively, were also compared.

RESULTS

Glucose concentrations increased steadily from group 1 to 5 in a stepwise manner. The initial differences in mean glucose concentrations reaching statistical significance occurred 1) between groups 1 and 2 (6.4 vs. 7.7 mmol/l, P = 0.0004) for daytime postprandial periods, followed by differences; 2) between groups 2 and 3 (7.5 vs. 9.3 mmol/l, P = 0.0003) for the morning periods (dawn phenomenon); and finally 3) between groups 3 and 4 (6.3 vs. 8.4 mmol/l, P < 0.0001) for nocturnal fasting periods.

CONCLUSIONS

The deterioration of glucose homeostasis in individuals with type 2 diabetes progressed from postprandial to fasting hyperglycemia following a three-step process. The first step related to the three diurnal postmeal periods considered as a whole, the second step occurred during the morning period, and the third and final step corresponded to sustained hyperglycemia over the nocturnal fasting periods. Such a description of the key stages in the evolution of type 2 diabetes may be of interest for implementing antidiabetes treatment.

Effect of pre-analytical variables on glycohemoglobin measurements in routine clinical care

OBJECTIVES

To analyze the contribution of the labile A1C fraction (L-A1C) and sample storage conditions on GHb measurements.

DESIGN AND METHODS

L-A1C separation (HPLC Hitachi L-9100) was evaluated before and after sample treatment by four different methods for L-A1C removal. Different sample storage conditions were analyzed.

RESULTS

L-A1C may overestimate up to 1.64% total A1C if not properly separated. Samples were stable for up to 10, <1, and at least 100 days for whole blood stored at 4, -20, and -80 degrees C, respectively.

CONCLUSIONS

The presence of L-A1C may overestimate GHb results. Samples may be kept under refrigeration up to 10 days and at -80 degrees C if long-term storage is required.