HbA1c Assay Research Articles

A quartz crystal microbalance-based biosensor for enzymatic detection of hemoglobin A1c in whole blood

Abstract Here we present a quartz crystal microbalance (QCM) biosensor for enzymatic detection of hemoglobin A1c (HbA1c). It shows average plasma glucose concentration readings over the prior three months. HbA1c can be quantitatively measured based on changes of resonance frequency of QCM following mass changes on QCM sensor surface. These mass changes were caused by size enlargement of conjugated gold nanoparticle with thiol-terminated SAMs on the sensor surface due to gold staining by hydrogen peroxide (H2O2) generated from enzymatic HbA1c assay. Finally, we investigated sensor responses due to mass changes on various concentrations of applied H2O2. We also demonstrated its capability for analyzing HbA1c in whole blood sample with enzymatic assay. Our results showed that the proposed QCM biosensor could quantitatively analyze HbA1c with a detection limit of 0.147% HbA1c with respect to hemoglobin and a coefficient variation of less than 10%.

HbA1c monitoring interval in patients on treatment for stable type 2 diabetes. A ten-year retrospective, open cohort study

[Aims] This study aims to suggest an informative interval for HbA1c in DM patients with stable glycemic control, based on test characteristics of the HbA1C assay using the signal-to-noise ratio method. [Methods] This was a retrospective, open cohort study. Data were collected between January 2005 to December 2014 at a tertiary-level community hospital in Japan. All adult patients aged under 75 years, with stable glycemic control on a first pharmaceutical regimen for Type II diabetes, and at least two HbA1c measurements after they achieved glycemic stability, were included in the analysis. We defined stable glycemic control as HbA1c <7.0% (52 mmol/mol) and requiring no change in the medication regimen after three consecutive measurements. We adapted a signal-to-noise method for distinguishing true change from measurement error by constructing a linear random effects model to calculate signal and noise for HbA1c. The screening interval for HbA1c was defined as informative when the signal-to-noise ratio exceeded 1. [Results] Among 1066 adults with diabetes, 639 patients (18.5%) were identified as achieving stable glycemic control (511 male (67.3%)), with a mean HbA1c (SD) of 6.4 (0.4)% (46 mmol/mol). Patients with stable glycemic control increase their HbA1c 0.27% (3 mmol/mol) every year while HbA1c has 0.32% (3.5 mmol/mol) noise, as testing characteristics. Signal exceeds noise after 1.2 years (95%CI: 0.9–1.6). [Conclusion] Once patients achieve stable glycemic control at their HbA1c goal, an informative interval for HbA1c monitoring is once every year. Current guidelines, which suggest testing every six months, may contribute to substantial over-testing.

URINARY MARKERS OF OXIDATIVE DNA DAMAGE IN TYPE 1 DIABETIC CHILDREN: RELATION TO MICROVASCULAR COMPLICATIONS

Objective: Type 1 diabetes mellitus (T1DM) is a widespread metabolic disease, which frequently carries with it a significant impact on human health. Oxidative damage and tissue inflammation have been claimed to be a typical pathogenic component for the progression of diabetic complications. We aim in this study to explore the relation of urinary 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG) (as a marker of nucleic acid oxidation) to microvascular complications in T1DM.Methods: A case–control study, enrolling 45 T1DM children and an equivalent number of healthy subjects, was performed. Full clinical examination and anthropometric measurement were performed to all subjects. Urinary assessment for 8-oxodG and albumin was done in addition to blood sampling for lipid profile and glycated Hb (HbA1c) assay. Complete ocular examination for assessment of diabetic retinopathy (DR) was also done.Results: Levels of urinary 8-oxodG, serum cholesterol, triglycerides, and low-density lipoprotein in cases were significantly higher than non-diabetics; these levels were likewise higher in uncontrolled T1DM patients in comparison with well-controlled T1DM subjects. Urinary 8-oxodG and HbA1c were significantly higher in diabetic patients with albuminuria and DR compared to patients without complications. Significant positive correlation was found between 8-oxodG with HbA1c (r=0.8, p&lt;0.01), diastolic blood pressure (DBP) (r=0.4, p=0.02), and cholesterol (r=0.4, p=0.05).Conclusion: Urinary 8-oxodG was found to be a reliable marker for assessing oxidative DNA damage in T1DM and can be used in the determination of microvascular complications related to diabetes.

Labile glycated haemoglobin and carbamylated haemoglobin are still critical points for HbA1c measurement

IntroductionHaemoglobin A1c (HbA1c) is a key analyte for the monitoring of glycemic balance in diabetic patients and is used for diabetes diagnosis in many countries. The potential interference of carbamylated haemoglobin (cHb) and labile glycated haemoglobin (LA1c) on HbA1c assays must remain a matter of vigilance. Such a situation has occurred in our laboratory with a kit replacement on the Bio-Rad Variant™ II testing system, a cation-exchange high performance liquid chromatography (HPLC) system. With this method, LA1c and cHb coeluted in a same peak which may have different consequences on HbA1c values.Materials and methodsThe influence of increasing LA1c and cHb values on HbA1c results was studied with in vitro glycation and carbamylation of samples. Samples from patients with high and normal blood urea concentrations were assayed by HPLC and immunological assay.ResultsWe observed that the degree of interference greatly varied depending on the nature of the interfering Hb fractions found under the so-called “LA1c peak”. Thus, we have decided to apply a decision tree using “LA1c” thresholds depending on: (i) the retention time, (ii) the shape of the peak, (iii) other analytes, like urea. If the peak recognized as “LA1c” is mainly formed by LA1c, we consider that there is no interference until 4%. If the peak is mainly formed by cHb, we consider an interference threshold equal to 2%.ConclusionsThis situation reminds that cHb and LA1c remain critical issues in chromatography-based HbA1c assays and that adapted criteria must be set up for result interpretation.

Investigation and Analysis of Hemoglobin A1c Measurement Systems' Performance for 135 Laboratories in China.

Background:Hemoglobin A1c (HbA1c) measurement is of great value for the diagnosis and monitoring of diabetes. Many manufacturers have developed various experiments to determine the HbA1c concentration. However, the longitudinal use of these tests requires strict quality management. This study aimed to analyze the quality of HbA1c measurement systems in China using six sigma techniques to help improve their performances.Methods:A total of 135 laboratories were involved in this investigation in 2015. Bias values and coefficients of variation were collected from an HbA1c trueness verification external quality assessment program and an internal quality control program organized by the National Center of Clinical Laboratories in China. The sigma (σ) values and the quality goal index (QGI) were used to evaluate the performances of different groups, which were divided according to principles and instruments.Results:The majority of participants (88, 65.2%) were scored as “improvement needed (σ < 3)”, suggesting that the laboratories needed to improve their measurement performance. Only 8.2% (11/135) of the laboratories were scored as “world class (σ ≥ 6)”. Among all the 88 laboratories whose σ values were below 3, 52 (59.1%) and 23 (26.1%) laboratories needed to improve measurement precision (QGI <8.0) and trueness (QGI >1.2), respectively; the remaining laboratories (13, 14.8%) needed to improve both measurement precision and trueness. In addition, 16.1% (5/31) and 15.0% (3/20) of the laboratories in “TOSOH” and “ARKRAY” groups, respectively, were scored as “world class”, whereas none of the laboratories in “BIO-RAD” group were scored as “world class”.Conclusions:This study indicated that, although participating laboratories were laboratories with better performance in China, the performances were still unsatisfactory. Actions should be taken to improve HbA1c measurement performance before we can include HbA1c assays in diabetes diagnosis in China.

Effects of hemoglobin variants HbJ Bangkok, HbE, HbG Taipei, and HbH on analysis of glycated hemoglobin via ion-exchange high-performance liquid chromatography.

To explore the effects of HbJ Bangkok, HbE, HbG Taipei, and α-thalassemia HbH on the results of HbA1c assessment using ion-exchange high-performance liquid chromatography (IE-HPLC). We enrolled five patients in which the results of the IE-HPLC HbA1c assay were inconsistent with the average levels of FBG. We performed hemoglobin capillary (Hb) electrophoresis using whole-blood samples. We also sequenced the genes encoding Hb using dideoxy-mediated chain termination and analyzed HbA1c using borate affinity HPLC (BA-HPLC) and turbidimetric inhibition immunoassay (TINIA). Two patients had the HbJ Bangkok variant. Hb genotypes of these patients were β41-42 /βJ Bangkok and βN /βJ Bangkok , and the content of HbJ Bangkok was 93.9% and 52.4%, respectively. The remaining three patients had the following: HbE (βN /βE Hb genotype, 23.6% HbE content), HbG Taipei (βN /βG Taipei Hb genotype, 39.4% HbG Taipei content), and α-thalassemia HbH (6.1% HbH content, 2.8% Hb Bart's content). In the patients with β-thalassemia and HbJ Bangkok variants, the presence of the variants interfered with the results of HbA1c analyses using IE-HPLC and TINIA; in the remaining four patients, there was interference with the results of HbA1c IE-HPLC but not with the TINIA assay. There was no interference with BA-HPLC HbA1c results. HbJ Bangkok, HbE, HbG Taipei Hb, and α-thalassemia HbH disease cause varying degrees of interference with the analysis of HbA1c using IE-HPLC. In these patients, we suggest using methods free from such interference for the analysis of HbA1c and other indicators to monitor blood glucose levels.

Digital Health Care by In Silico Glycation of HbA1 Blood Cells.

Diabetes health care relies on the HbA1c (A1c) assay and associated average glucose (AG) to evaluate and control chronic glycemia. However, the A1c assay is plagued with significant noise, lag time, and specificity issues. Current studies support the significant health care advantage of clinical action based on real-time blood glucose (BG) metrics. We seek to improve diabetes management by directly relating such metrics to AG levels as mediated by recently discovered recurrent endocrine cycles. Several studies collected multiple months of BG data on 111 subjects totaling 261 893 CGM measurements and 29 278 meter readings. These data are a rich source of multiday metrics in terms of the CGM and SMBG daily profiles. The recurrent endocrine patterns expose key metric relationships for monitoring AG related to A1c using CGM and SMBG data. Consequently, day-to-day tracking of AG is expressed as a simple two-parameter function of fasting BG for all studies. Consequently, when applied to 2518 qualified days of 64 subjects, the function predicts daily AG values with 2% relative standard error. All studies produced compatible results. By restricting one parameter to a constant, the error increased to 3%. The recurrent endocrine patterns revealed a persistent structure hidden within the multiday fluctuations that becomes a simple meter-compatible equation that accurately measures real-time trending of AG using fasting BG values. This enables a digital health monitoring service and self-monitoring device that reveals immediate disease progression as well as the impact of interventions and medications better than possible with the A1c assay.

Incidental Detection of a Rare Hemoglobin Variant (Hemoglobin N Seattle) Leading to Undetectable Levels of HbA1c in a Diabetic Female: A Case Report

Glycosylated hemoglobin (GHb) is routinely used to monitor glycemic control over past 2–3 months in diabetics. As per the recommendations of the American Association of Clinical Endocrinologist, 2007 values should be maintained below 7% to prevent the risk of chronic complications. We report a case of a 55-year old female patient with spuriously low HbA1c values by high-performance liquid chromatography. Suspecting the presence of any abnormal hemoglobin, capillary zone electrophoresis was done which identified the presence of Hb variant corresponding to -Hb N Seattle. Our case highlights that clinical laboratories should be aware of limitations of their HbA1c assay methods as well as rule out any possible interfering Hb variants.

Hb variants in Korea: effect on HbA1c using five routine methods.

Quantification of glycated hemoglobin (HbA1c) is a challenge in patients with hemoglobin (Hb) variants. We evaluated the impact of various Hb variants on five routine HbA1c assays by comparing with the IFCC reference measurement procedure (RMP). Whole blood samples showing warning flags or no results on routine HPLC HbA1c assays were confirmed for Hb variants and were submitted to HbA1c quantification using Sebia Capillarys 2 Flex Piercing, Roche Tina-quant HbA1c Gen. 2, Bio-Rad Variant II Turbo 2.0, ADAMS HA-8180, Tosoh G8 standard mode, and IFCC RMP using LC-MS. Among 114 samples, the most common variants were Hb G-Coushatta (n=47), Queens (n=41), Ube-4 (n=11), Chad (n=4), Yamagata (n=4), G-His-Tsou (n=2), G-Taipei (n=1), Fort de France (n=1), Hoshida (n=1), and two novel variants (Hb α-globin, HBA 52 Gly>Cys and Hb β-globin, HBB 146 His>Asn). In terms of control samples, all the result of HbA1c were "acceptable", within the criteria of ±7% compared to IFCC RMP target values. However, percentage of "unacceptable" results of samples with Hb variants were 16% for Capillarys 2, 7% for Tina-quant, 51% for Variant II Turbo 2.0, 95% for G8 standard mode, and 89% for HA-8180. The Capillarys 2 and HA-8180 assay did not provide the results in 5 and 40 samples with Hb variants, respectively. HbA1c results from five routine assays in patients with relatively common Hb variants in Korea showed various degrees of bias compared to those of IFCC RMP. Therefore, laboratories should be aware of the limitation of their methods with respect to interference from Hb variants found commonly in their local population and suggest an alternative HbA1c quantification method.

494: Positivity thresholds of HbA1c assay as a screening test for gestational diabetes mellitus in the first trimester in high-risk populations

494: Positivity thresholds of HbA1c assay as a screening test for gestational diabetes mellitus in the first trimester in high-risk populations

Ketosis-prone atypical diabetes in Cameroonian people with hyperglycaemic crisis: frequency, clinical and metabolic phenotypes.

It is unclear whether ketosis-prone diabetes is a specific type or a subtype of Type 2 diabetes. We aimed to describe the clinical and metabolic features of ketosis-prone diabetes in a sub-Saharan population. We consecutively enrolled and characterized 173 people with non-autoimmune diabetes admitted for hyperglycaemic crisis at the Yaoundé Central Hospital, Cameroon. Blood samples were collected for fasting glucose, HbA1c , lipid profile and C-peptide assays with insulin resistance and secretion estimation by homeostasis model assessment. People were classified as having Type 2 diabetes (n = 124) or ketosis-prone diabetes (n = 49). Ketosis-prone diabetes was sub-classified as new-onset ketotic phase (n = 34) or non-ketotic phase (n = 15). Ketosis-prone diabetes was found in 28.3% of the hyperglycaemic crises. Age at diabetes diagnosis was comparable in Type 2 and ketosis-prone diabetes [48 ± 14 vs 47 ± 11 years; P = 0.13] with a similar sex distribution. Overall BMI was 27.7 ± 13.4 kg/m2 and was ≥ 25 kg/m2 in 55.8% of those taking part, however, 73.5% of those with ketosis-prone diabetes reported weight loss of > 5% at diagnosis. Blood pressure and lipid profile were comparable in both types. Ketosis-prone diabetes in the ketotic phase was characterized by lower insulin secretion and higher serum triglycerides compared with non-ketotic ketosis prone and Type 2 diabetes. Type 2 and ketosis prone diabetes in the non-ketotic phase were comparable in terms of lipid profile, blood pressure, waist-to-hip ratio, BMI and fat mass, insulin secretion and insulin resistance indices. Ketosis-prone diabetes is likely to be a subtype of Type 2 diabetes with the potential to develop acute insulinopenic episodes.

Membership in a diabetes-care network and adherence to clinical practice guidelines for treating type 2 diabetes among general practitioners: A four-year follow-up

ObjectivesTo assess whether private general practitioners (GPs) belonging to a diabetes-care network adhered more closely to clinical practice guidelines for diabetes care than GPs not in such a network, for all their patients with type 2 diabetes treated with medication (patients with diabetes), regardless of whether they received care through a network (that is, whether a halo effect occurred). Research design and measuresThe study, based on health insurance reimbursement databases in southeastern France, included 468 GPs in two networks and 468 non-network GPs in the same geographical area, matched one-to-one by propensity scores. We followed up their patients with diabetes (n=22,808) from 2008 through 2011, conducting multivariate time-to-event analyses (Cox models) that took the matching design into account to evaluate time from inclusion until performance of the given number of each of six recommended examinations/tests. ResultsGPs belonging to a diabetes-care network adhered more closely to clinical practice guidelines but our result were slightly pronounced. Hazard ratios (HR) were significantly higher for patients of network GPs for the implementation of 3 HbA1C assays (HRa=1.13; [95%CI=1.10–1.16]), or 1 microalbuminuria assay (1.4 [1.35–1.45]); they were lower for LDL-cholesterol assays (1.04 [1.01–1.07]) and ophthalmological checkups (1.07 [1.04–1.10]), and not significant for creatinemia or cardiac monitoring. ConclusionsNetwork GPs had better diabetes monitoring practices for all their patients with diabetes than the other GPs, especially for the most diabetes-specific tests. Further research is needed in other settings to confirm the existence of this halo effect.

HbA1c: EQA in Germany, Belgium and the Netherlands using fresh whole blood samples with target values assigned with the IFCC reference system.

External quality assessment/proficiency test (EQA/PT) organizers play an important role in monitoring the performance of HbA1c measurements. With increasing quality of the assays, HbA1c is increasingly used for diagnosis of diabetes and the demands on EQA/PT organizers themselves are rising constantly. EQA organizers in Germany (INSTAND), Belgium (WIV/IPV), and the Netherlands (SKML) organized a program with commutable samples and target values assigned with the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) reference system. The aim of this project was to confirm the logistic feasibility of organizing synchronically in the three countries, an accuracy-based EQA program with fresh whole blood, to investigate the performance of HbA1c assays within and across countries and manufacturers, and to review the EQA acceptance limits. Throughout 2015, ten fresh whole blood samples were supplied to the participants. Aggregated results were evaluated according to the IFCC model for quality targets at four levels: overall, per country, per manufacturer, and per country per manufacturer. Robust results in summer and winter demonstrated the feasibility of organizing an EQA with fresh whole blood samples in three countries. The overall performances, as well as the performance for each country were very similar: results fell within the IFCC criteria. Although substantial differences between results from different manufacturers were present, the performances of laboratories using tests of the same manufacturer were strikingly similar in the three countries, suggesting that the quality of HbA1c assays is for the most part manufacturer- related. The improved design of the EQA program also suggested that acceptance limits for performance can be reduced to approximately 8%.

A prospective comparison of the AUSDRISK and HbA1c for persons with spinal cord injury

Objective: The primary object of this study was to determine the validity of the Australian Type 2 Diabetes Risk Assessment Tool (AUSDRISK) for predicting the development of type 2 diabetes in persons with spinal cord injury (SCI). Design and setting: The prospective comparative study (December 2013-March 2014) collected data on AUSDRISK and haemoglobin A1c (HbA1c) in participants’ homes. Participants: Participation rate was 67% (n=79). Study criteria: over 18 years of age, a SCI for more than 12 months, living at home, wheelchair dependant and no diabetes diagnosis. Main outcome measures: AUSDRISK sensitivity and specificity in predicting incident type 2 diabetes in persons with SCI. Results: Of the 79 participants, 81% were male, mean age was 53 years (SD 14.14) with 23.2years (median 23; SD +/- 13.2yrs) since injury. There was a positive correlation between length of time since SCI and risk score (AUSDRISK) (r = .242, p = .032). Participants with high AUSDRISK scores had higher HbA1c% (5.38 versus 5.2, p = .026) level. The high risk classification explained a moderate amount of HbA1c % (area under curve = .651; 95% CI .53 - .77). The level of HbA1c which had the highest sensitivity (.59) and specificity (.73) for risk classification was 5.25%. Waist circumference and physical activity items require further powered studies to determine if appropriately weighted. Conclusion: Comparing the AUSDRISK with HbA1c assays, the AUSDRISK can predict type 2 diabetes risk in a person with S

Hb Belluno [β111(G13)Val→Gly;β133(H11)Val→Val (HBB: c.335T > G;402G > C)]: Incidental Detection of a New Clinically Silent β Chain Variant During Hb A1c Determination by High Performance Liquid Chromatography

A previously unreported β chain variant, Hb Belluno [β111(G13)Val→Gly;β133(H11)Val→Val (HBB: c.335T > G;402G > C)], was incidentally discovered in a woman suffering from diabetes, during glycated hemoglobin (Hb A1c) assay. Its presence was suspected because of a small abnormal peak with a retention time just shorter than that of normal Hb A1c. Standard high performance liquid chromatography (HPLC), capillary zone electrophoresis (CZE) and agarose gel electrophoresis did not allow to separate the variant from Hb A. The reversed phase HPLC of globin chains showed the presence of a heterozygous β-globin variant amounting to approximately 43.5% of the total β chains. Later, this variant was found in five other members of the same family and DNA sequencing analysis confirmed a β-globin gene mutation. The variant is clinically silent in all patients and showed a slight instability with both heat and isopropanol tests. The other three mutations at this locus also affect stability. Hemoglobin (Hb) variants may invalidate the results of Hb A1c analysis and could result in mismanagement of diabetes. A comment alerting the requesting clinician to the presence of the Hb variant must be appended to the Hb A1c result. Additionally, many Hb variants can be chromatographically and/or electrophoretically silent. Therefore, when the clinician suspects a variant Hb, it is not sufficient to get a negative response from an HPLC screening test to rule it out. A dialogue with the pathologist is essential, involving exchange of information and sharing a diagnostic work-up including surveys to assess Hb stability and oxygen affinity, as much as DNA sequencing.

Development of filter paper hemoglobin A1c assay applicable to newborn screening

PurposeGestational diabetes influences risk for future metabolic disease including type 2 diabetes. Hemoglobin A1c (HbA1c) measurement assesses hemoglobin A glycosylation, and could theoretically be used as a test to estimate gestational glucose exposure. HbA1c assay on dried blood spots (DBS) is needed before potential application to statewide newborn screening (NBS) population studies. The study aimed to establish a reliable method to measure HbA1c on NBS DBS specimens. De-identified blood was used to generate trials to evaluate stability of HbA1c in DBS, optimal elution time, and stability of eluted blood. ResultsAnalysis of DBS stability HbA1c measurements from 3 to 6days after collection overestimated HbA1c values by a bias factor between 0.83 and 0.87. Sixty minutes of elution time produced maximal reproducibility and minimal bias of results. Within assay standard deviation: 0.058; average bias: −0.02%. Stability of eluted blood did not vary significantly between days 0–2 after DBS elution. ConclusionsMeasurement of HbA1c levels on DBS from human blood is feasible. Results suggest new method using DBS to measure HbA1c level with the following characteristics: optimal time for sample analysis 3–6days after collection, elution time of 60min and eluted blood analysis within 2days of elution. Measurement of neonatal HbA1c could provide insight regarding the infant's in utero exposure to glucose.

Methods, units and quality requirements for the analysis of haemoglobin A1c in diabetes mellitus.

The formation of glycohemoglobin, especially the hemoglobin A1c (HbA1c) fraction, occurs when glucose becomes coupled with the amino acid valine in the β-chain of Hb; this reaction is dependent on the plasma concentration of glucose. Since the early 1970s it has been known that diabetics display higher values OF HbA1C because they have elevated blood glucose concentrations. Thus HbA1c has acquired a very important role in the treatment and diagnosis of diabetes mellitus. After the introduction of the first quantitative measurement OF HbA1C, numerous methods for glycohemoglobin have been introduced with different assay principles: From a simple mini-column technique to the very accurate automated high-pressure chromatography and lastly to many automated immunochemical or enzymatic assays. In early days, the results of the quality control reports for HbA1c varied extensively between laboratories, therefore in United States and Canada working groups (WG) of the Diabetes Controls and Complications Trial (DCCT) were set up to standardize the HbA1c assays against the DCCT/National Glycohemoglobin Standardization Program reference method based on liquid chromatography. In the 1990s, the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) appointed a new WG to plan a reference preparation and method for the HBA1c measurement. When the reference procedures were established, in 2004 IFCC recommended that all manufacturers for equipment used in HbA1c assays should calibrate their methods to their proposals. This led to an improvement in the coefficient of variation (CV%) associated with the assay. In this review, we describe the glycation of Hb, methods, standardization of the HbA1c assays, analytical problems, problems with the units in which HbA1c values are expressed, reference values, quality control aspects, target requirements for HbA1c, and the relationship of the plasma glucose values to HbA1c concentrations. We also note that the acceptance of the mmol/mol system for HbA1c as recommended by IFCC, i.e., the new unit and reference ranges, are becoming only slowly accepted outside of Europe where it seems that expressing HbA1c values either only in per cent units or with parallel reporting of percent and mmol/mol will continue. We believe that these issues should be resolved in the future and that it would avoid confusion if mmol/mol unit for HbA1c were to gain worldwide acceptance.

Comparison between the Oral Glucose Tolerance Test and the Hba1c Assay for Detecting Impaired Glucose Regulation in Bahamian Adolescents

Objective: To determine the best method for detecting Impaired Glucose Regulation (IGR) in adolescents from New Providence Island, Bahamas. IGR is defined by blood glucose levels that are higher than normal but below those of a person with diabetes. Design and Methods: From Jan-March 2012, 873 adolescents (13-19 years old) were randomly selected from five different high schools in New Providence. Weight and height were measured and participants were screened for IGR using the hemoglobin A1c (HbA1c) test and a 2-hour oral glucose tolerance test (OGTT). T-test or chi-square test was used to determine significant associations between sex and outcome variables, and prevalence of glycemic status by BMI category. Linear regression was used to determine the relationship between OGTT results and BMI. Results: Of the initial pool, 861 adolescents (98.6%) completed the study. The OGTT demonstrated that 89.4% of these students had normal fasting glucose levels and 98.8% had normal 2-hour OGTT glucose levels. Eightyseven students (37 boys and 50 girls) had elevated fasting plasma glucose; however, 2 hours after the oral glucose load, only 9 students (2 boys and 7 girls) had blood glucose concentrations indicative of IGR. For the HbA1c test, 82.6% of the students had normal results, and 1.3% had diabetes. The HbA1c test revealed a higher percentage of students with IGR (16.1%) than the OGTT (1%). Conclusions: The HbA1c test identified a greater percentage of adolescents as having IGR than did the OGTT. Due to the high discordance between the two tests, it is likely that an elevated HbA1c test may falsely classify adolescents as IGR if OGTT results and clinical signs (e.g., diabetic retinopathy and/or nephropathy) are not considered.

Stability and reliability of glycated haemoglobin measurements in blood samples stored at − 20 °C

AimTo validate the stability of glycated haemoglobin (HbA1c) measurements in blood samples stored at −20°C for up to one month. MethodsThe study group comprised 142 type 2 diabetic subjects visiting a tertiary centre for diabetes at Chennai city in south India. The HbA1c assay was done on a fasting blood sample using the Bio-Rad Variant machine on Day 0 (day of blood sample collection). Several aliquots were stored at −20°C and the assay was repeated on the 3rd, 7th, 15th, and 30th day after the sample collection. Bland–Altman plots were constructed and variation in the HbA1c levels on the different days was compared with the day 0 level. ResultsThe median differences between HbA1c levels measured on Day 0 and the 3rd, 7th, 15th, and 30th day after blood collection were 0.0%, 0.2%, 0.3% and 0.5% respectively. Bland–Altman plot analysis showed that the differences between the day ‘0’ and the different time points tend to get larger with time, but these were not clinically significant. ConclusionsHbA1c levels are relatively stable up to 2weeks, if blood samples are stored at −20°C.

Comparing the HbA1c Assay Results of Architect C 8000 and MQ-2000PT

Objective: Changes in a device and the modification of measurement methods are frequent issues in medical laboratories. The effects of such modifications on assay results should be investigated. HbA1c is a widely used analyte in treatment and in the follow-up of diabetic patients. We aimed to evaluate the effects of two different assay methods on the detection of the percentage of HbA1c. Methods: We used blood samples with K3-EDTA of 57 diabetic patients who were admitted to our laboratories for the HbA1c assay. HbA1c assays were performed using immunoturbidimetric (Architect C 8000; Abbot Laboratories Inc., Middletown, USA) and ion exchange chromatography (MQ2000PT; Shanghai Hui Zhong Medical Technology Co. Ltd., Shangai, China) methods. HbA1c assays were repeated two times in both devices. Results were analyzed using MedCalc software. Results: Mean HbA1c level in immunoturbidimetric and ion exchange chromatography assays were 6.6 (min:4.1 and max:11.4) and 6.9 (min:4.9 and max:11.8), respectively. In the linear regression analysis, we detected an r value of 0.9533 (r<0.975). In Passing–Bablock analysis, we found the following equation, y=0.4+1.0 x (intercept CI:−0.22−0.68; slope CI:0.97−1.09). We did not observe any constant or proportional systematic errors between the assay methods. We found a 0.37 difference between the two methods in the Bland–Altman graphs of mean HbA1c measurements (Bias 5.7%). Conclusion: Researches on the harmonization of HbA1c are still increasing worldwide. However, at present, there are variations in methods and devices. NGSP suggests that the difference between methods should not exceed HbA1c±0.70. We found that mean HbA1c results were higher by 0.37 times in ion exchange chromatography assay compared with those in immunoturbidimetric assay. This difference is within the range suggested by NGSP. (JAREM 2015; 5: 52-5)