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

Is it feasible for European laboratories to use SI units in reporting results?

The ultimate goal of harmonization, crucial to quality in laboratory medicine, is to improve patient outcomes by providing accurate, actionable laboratory information. Patients and healthcare professionals assume that clinical laboratory tests performed by different laboratories at different times on the same type of sample are comparable, and that results can be reliably and consistently interpreted. In this context the reporting units for tests can have a considerable influence on the numeric result. The harmonization of measurement units in laboratory report, leads to the provision of interchangeable and comparable results, thus maximizing the validity of laboratory information, and assuring a more accurate diagnosis and better treatment for the patient. However, although considerable efforts have been made in recent years, the criticisms continue. This opinion paper, prepared jointly by EFLM Committee Harmonization (C-H) and Committee Postanalytical phase (C-POST), describes the "general pragmatic approach" proposed in the drafting of guidelines for the harmonization of measurement units in reporting results, in order to ensure they are used as widely as possible.

The Performance of Three Systems of Glycated Hemoglobin Measurements Among Patients With Sickle Cell Trait in Basrah, Iraq

Background Hemoglobin variants may cause mismanagement of diabetes resulting from false glycated hemoglobin (HbA1c) results. The aim of this study was to compare the results obtained from three different HbA1c assay systems among patients with sickle cell trait (SCT) at Faiha Specialized Diabetes, Endocrine, and Metabolism Center (FDEMC) in Basrah. Methods A cross-sectional observational study was done in FDEMC in Basrah on patients with established diagnoses of diabetes mellitus. All samples were analyzed at FDEMC laboratory by using three different systems: Roche Cobas Integra Gen.2 (COBAS INTEGRA® 400 plus analyzer immunoassay) (Roche Diagnostics, Indianapolis, IN), a turbidimetric inhibition immunoassay (TINIA), Bio-Rad Variant II Turbo (Bio-Rad, Hercules, CA) Ion exchange HPLC method, and Bio-Rad D-10 (A1c program) (Bio-Rad, Hercules, CA) Ion exchange HPLC method. Results We enrolled 139 persons with diabetes and SCT compared with 70 controls with diabetes and no SCT. A significant difference in the mean HbA1c levels between Roche Cobas Integra Gen.2 and Bio-Rad Variant II Turbo in comparison with Bio-Rad D-10 (A1c program) across all strata of HbA1c in SCT. The highest difference was -0.5% in the stratum of HbA1c 7 to 9% group in Roche Cobas Integra Gen.2, while it was +0.8% in the stratum of HbA1c less than 7% in the SCT group. For the control group, the highest difference was -1.3%, seen in the stratum of HbA1c, more than 9% in the Roche Cobas Integra Gen.2, while the highest difference in the Bio-Rad Variant II Turbo was +0.5% in the same stratum. In both groups, the results of HbA1c were mostly higher in the Bio-Rad Variant II Turbo and lower in Roche Cobas Integra Gen.2. Conclusion Roche Cobas Integra Gen.2 and Bio-Rad Variant II Turbo methods are not preferred to be used in HbA1c estimation in areas where SCT is prevalent. Diagnosing or follow-up of glycemic control in patients with SCT needs critical reappraisal because of the limitation of methods used to measure HbA1c in Basrah.

Evolving Clinical Features of Diabetic Ketoacidosis: The Impact of SGLT2 Inhibitors

Background/Objectives: The antidiabetic effect of SGLT2 inhibitors (SGLT2-is) is based on their ability to increase glucose excretion through urine by inhibiting the kidney-resident SGLT2 protein. Euglycemic diabetic ketoacidosis (EuDKA) is an uncommon but potentially life-threatening adverse effect of these medications, which are notable for their antidiabetic, cardiovascular, and renal protective properties. This study aimed to clarify the impact of SGLT2-is on demographic, clinical, and biochemical characteristics in patients with DKA. Methods: A total of 51 individuals with a diagnosis of DKA were included in the trial; 19 of these patients were treated with SGLT2-is, while 32 were not. Patients diagnosed with DKA and treated with SGLT2-is were compared to those not treated with the medication in terms of clinical, biochemical, and laboratory characteristics. Results: The age of patients utilizing SGLT2-is was statistically considerably greater than that of non-users (p < 0.001). EuDKA was exclusively noted in the SGLT2-is cohort (p = 0.005). Urinary tract infections, vulvovaginitis, and genitourinary infections were substantially more prevalent among SGLT2-i users compared with non-users among both women and the overall patient group (p = 0.036, p = 0.001, p = 0.005, p = 0.003, respectively). Plasma glucose concentrations were significantly higher in SGLT2-i non-users (p = 0.006). Chloride (Cl-) concentrations were elevated among SGLT2-i users (p = 0.036). Conclusions: The study findings indicate that SGLT2 inhibitors may substantially influence age, serum chloride, EuDKA, and the occurrence of genitourinary infections in individuals with DKA.

Revealing a Third Dissolved-Phase Xenon-129 Resonance in Blood Caused by Hemoglobin Glycation

Hyperpolarized (HP) xenon-129 (¹²⁹Xe), when dissolved in blood, has two NMR resonances: one in red blood cells (RBC) and one in plasma. The impact of numerous blood components on these resonances, however, has not yet been investigated. This study evaluates the effects of elevated glucose levels on the chemical shift (CS) and T2* relaxation times of HP ¹²⁹Xe dissolved in sterile citrated sheep blood for the first time. HP ¹²⁹Xe was mixed with sheep blood samples premixed with a stock glucose solution using a liquid-gas exchange module. Magnetic resonance spectroscopy was performed on a 3T clinical MRI scanner using a custom-built quadrature dual-tuned ¹²⁹Xe/¹H coil. We observed an additional resonance for the RBCs (¹²⁹Xe-RBC1) for the increased glucose levels. The CS of ¹²⁹Xe-RBC1 and ¹²⁹Xe-plasma peaks did not change with glucose levels, while the CS of ¹²⁹Xe-RBC2 (original RBC resonance) increased linearly at a rate of 0.015 ± 0.002 ppm/mM with glucose level. ¹²⁹Xe-RBC1 T2* values increased nonlinearly from 1.58 ± 0.24 ms to 2.67 ± 0.40 ms. As a result of the increased glucose levels in blood samples, the novel additional HP ¹²⁹Xe dissolved phase resonance was observed in blood and attributed to the ¹²⁹Xe bound to glycated hemoglobin (HbA_1c).

Metabolic Syndrome and Cardiometabolic Risk Factors in the Mixed Hypercholesterolemic Populations with Respect to Gender, Age, and Obesity in Asir, Saudi Arabia

This record study aimed to investigate the prevalence of metabolic syndrome (MetS) profiles regarding sex, age, and obesity for the riskier factor of cardiovascular diseases in a general population in Saudi Arabia. Laboratory and anthropometric measurements were performed on non-specific participants with variant ages and BMI in either sex. Serobiochemical changes were measured for metabolic profiles, i.e., A1C/FSG, TC, TGC, HDLC/LDLC, Vit.D, TSH/T4, Hb, and Cr. The study was applied in a Polyclinic, Abha, Saudi Arabia in 2020 G. The general population showed variable incidences of MetS profiles, such as 69.4% diabetes, 85.5% hypothyroidism, and 92.2% obesity. Hypothyroidism showed a higher incidence in women rather than in men, but men were more dyslipidemic, with higher TGC and LDLC but low HDLC, compared to women. Men <40 Y. showed diabetes and hypothyroidism, but elders were dyslipidemic. Women <40 Y. showed anemia and hypovitaminosis-D but were suffering from hypothyroidism at all ages. Diabetes, hypothyroidism, hypovitaminosis-D, and dyslipidemia were the main MetS components in both overweight and obese participants, and an incidence of more than 50% in each profile was recorded. Diabetes with hypertension was characteristic of obese participants rather than those overweight. About 66.1% of the mixed-hypercholesterolemic cases were diabetic, but 18.9% of the mixed-diabetic participants were hypercholesterolemic. Castelli's risk factors, CRI-I and CRI-II, and atherogenic indices, AIP and AC, were measured for evaluating the cardiac risk in different populations based on the AUC-ROC and cut-off values. Insulin-resistance marker (TyG) was also measured, showing considerable cut-off values for diabetic susceptibility in the lipidemic participants with higher TGC and TC rather than HDLC or LDLC. In conclusion, MetS showed higher susceptibility to sex and age with increased incidence in women rather than men. However, the cardiac risk was more susceptible to men of higher TGC and low HDLC than women. Type 2 Diabetes mellitus (T2DM) was more prominent in both elders (≥40 Y.) than younger ages of either sex. Anemia and deficiency of Vit. D was characteristic of young women (<40 Y.). Hypothyroidism affects young men <40 Y. but was recorded in women of all ages. Both dyslipidemia and diabetes could trigger CVD, showing higher cardiac risk in mixed-hypercholesterolemic men rather than women. Our study strongly suggests that the consumption of unhealthy junk food, tobacco smoking, lack of exercise, and physical inactivity could be conclusive evidence of MetS in the Saudi population.

Comparison of high performance liquid chromatography and turbidimetric inhibition immunoassay methods for measurement of hemoglobin A1c

Aim: Hemoglobin A1c is a valuable parameter for the diagnosis and follow-up of its diabetes mellitus since its biological variation is low, does not require preparation before the test, is not affected by acute stress, and has high preanalytical stability. HbA1c measurement by HPLC has been determined as the reference method by National Glycohemoglobin Standardization Program (NGSP) in USA; after that The International Federation of Clinical Chemistry (IFCC) defined another reference method which could be related with NGSP. In our study, we aim to compare the two NGSP-certified methods of HbA1c, which are high-performance liquid chromatography (HPLC) and turbidimetric inhibition immunoassay (TINIA). Material and Method: HbA1c levels of the patients were measured using two HPLC and one TINIA method in three different hospitals (Lab A, Lab B (Both are HPLC), and Lab C (TINIA), in which Lab A was served as a reference). Because of the lower precision values of LabB, we firstly conducted a method comparison study of 40 volunteers (Group 1). After that, corrective and preventive activities carried out and the precision values in LabB reached the desired range. Following this, another method comparison study consisting of 60 new volunteers (Group 2) was conducted. The statistical flow of this study complied with Clinical Laboratory Standards Institute (CLSI) EP09-A3; Precision studies, Blant-Altman and Passing Bablok regression analysis were performed. Results: The percentage of the mean difference between the two HPLC methods (LabA and LabB) was 3.1%. After corrective and preventive actions had been taken, the mean difference between the two HPLC methods decreased to 2.0%. A decrease in systematic bias was found in our study. Two HPLC methods can be used interchangeably in both Group 1 and Group 2. In Group 1; 95% CI of intercept and slope were found as (-1.41 to -0.30) and (1.03 to 1.22), respectively. In Group 2; 95% CI of intercept and slope were found as (-1.33 to -0.31) and (1.01 to 1.17), respectively. HPLC and TINIA methods could not be used interchangeable without affecting patient results and outcome in both Group 1 and Group 2. Conclusion: Our study concluded that TINIA and HPLC methods could not be used interchangeably without affecting patient results and outcome. Because of the methodology that clinical laboratories are used to, clinicians and clinical biochemists should collaborate on managing diabetes mellitus regarding diagnosis, treatment, and follow-up.

Trehalose Activates Hepatic and Myocardial Autophagy and Has Anti-Inflammatory Effects in db/db Diabetic Mice

Db/db mice (carrying a mutation in the gene encoding leptin receptor) show autophagy suppression. Our aim was to evaluate the effect of autophagy inducer trehalose on liver and heart autophagy in db/db mice and to study inflammation dysregulation and the suitability of chitinases’ expression levels as diabetes markers. Thirty-eight male db/db mice and C57/BL mice (control) were used. The db/db model manifested inflammation symptoms: overexpression of TNF-α in the spleen and underexpression of IL-10 in the liver and spleen (cytokine imbalance). Simultaneously, we revealed decreased expression of chitotriosidase (CHIT1) and acid mammalian chitinase (CHIA) in the liver of db/db mice. CHIA expression in db/db mice is significantly lower only in the spleen. Trehalose treatment significantly reduced blood glucose concentration and glycated hemoglobin. Treatment of db/db mice by trehalose was followed by increased autophagy induction in the heart and liver (increased autolysosomes volume density studied by morphometric electron-microscopic method). Trehalose exerted beneficial cardiac effects possibly via increased lipophagy (uptake of lipid droplets). The autophagy activation by trehalose had several positive effects on the heart and liver of db/db mice; therefore, lipophagy activation seems to be a promising therapy for diabetes.

Advanced glycation end-products (AGEs) are lower in prostate tumor tissue and inversely related to proportion of West African ancestry

BACKGROUND

The metabolism of normal prostate relies on glycolysis, with prostate cancer having reduced glycolysis and increased aerobic metabolism. Advanced glycation end products (AGEs) accumulate in tissues as a result of age and glycolytic rate. Differential AGE levels were recently observed in prostate cancer tissues. Herein we sought to quantify AGEs in benign and cancer prostate tissue in a diverse cohort of patients.

METHODS

Levels of the AGE Nε-(carboxylethyl)lysine (CML) were quantified by immunohistochemistry (IHC) in a tissue microarray which consisted of 3 cores from tumor and 2 cores from benign areas from 118 patients (87 African American and 31 European American). Ancestry informative markers for African Ancestry were available for 79 patients. Epithelial and stromal areas were quantified separately using an E-cadherin mask. CML levels were compared with clinical grade group and ancestry by mixed linear effect models. Age, prostate-specific antigen (PSA) levels, body mass index (BMI), and hemoglobin A1C were included as covariates.

RESULTS

CML levels were lower in areas of the tumor, for both epithelium and surrounding stroma, compared with benign, but did not significantly change with tumor grade group. Age, PSA levels, BMI, and hemoglobin A1C did not associate with CML levels. CML levels were inversely associated with the percentage of African Ancestry in all tissues.

CONCLUSIONS

The low CML levels in cancer may reflect the reduced glycolytic state of the tissue. The inverse relationship between African Ancestry and CML levels in both benign and cancer areas suggests a state of reduced glycolysis. It is yet to be determined whether altered glycolysis and CML levels are bystanders or drivers of carcinogenesis.

Global FT4 immunoassay standardization: an expert opinion review

OBJECTIVES

Results can vary between different free thyroxine (FT4) assays; global standardization would improve comparability of results between laboratories, allowing development of common clinical decision limits in evidence-based guidelines.

CONTENT

We summarize the path to standardization of FT4 assays, and challenges associated with FT4 testing in special populations, including the need for collaborative efforts toward establishing population-specific reference intervals. The International Federation of Clinical Chemistry and Laboratory Medicine Committee for Standardization of Thyroid Function Tests has undertaken FT4 immunoassay method comparison and recalibration studies and developed a reference measurement procedure that is currently being validated. Further studies are needed to establish common reference intervals/clinical decision limits. Standardization of FT4 assays will change test results substantially; therefore, a major education program will be required to ensure stakeholders are aware of the benefits of FT4 standardization, planned transition procedure, and potential clinical impact of the changes. Assay recalibration by manufacturers and approval process simplification by regulatory authorities will help minimize the clinical impact of standardization.

SUMMARY

Significant progress has been made toward standardization of FT4 testing, but technical and logistical challenges remain.

OUTLOOK

Collaborative efforts by manufacturers, laboratories, and clinicians are required to achieve successful global standardization of the FT4 assays.

Introduction of a national program for HbA1c testing in Guyana South America and initial results

Diabetes is an increasing challenge for low- and middle-income countries (LMIC) and access to HbA1c testing is limited. HbA1c, a measure of glycaemic control averaged over 3 months, provides both clinicians and policymakers with a tool to identify the risk of long-term diabetes comorbidity. We describe the steps used to implement standardised testing in Guyana South America and the initial results according to a locally developed protocol as part of a country-wide project to improve the care of people with all forms of diabetes The steps identified include: a standardised method traceable to a recognized international reference standard, participation in a quality control cycle with an international reference laboratory, a clinical pathway for testing to reduce inappropriate use and minimize resource wastage, training of technicians in operation and maintenance of equipment, identification of a suitable space with constant power supply, a reliable procurement system, education of healthcare professionals on interpretation and follow-up of results and feedback of programme results to improve clinical practice. Some steps for implementation of the national HbA1c testing program were initiated better than others. Initial unreliability of the service undermined confidence in the system. Failure to follow the testing protocol led to some patients being tested too soon and others too late. Cost of reagents was about 5.60 USD/test. We trained 340 people in diabetes care and knowledge was improved but were unable to assess whether it was appropriately applied. Over one third of people tested in the 30-70 age group had an HbA1c over 9% (75 mmol/mol) and this did not improve over the 5 years of testing. Despite the difficulties we think our unique experience of implementation of a nationwide HbA1c testing programme has important lessons for other LMICs.

Preventing misdiagnosis of diabetes in the elderly: age-dependent HbA1c reference intervals derived from two population-based study cohorts

BACKGROUND

Measurement of gylcated hemoglobin A1c (HbA1c) plays a central role in monitoring quality of antidiabetic therapy and in the diagnosis of diabetes. Several studies report increased levels of HbA1c in nondiabetic elderly. However, this observation did not reach incorporation into daily clinical practice or the respective guidelines. The present study aimed to evaluate HbA1c levels in relation to age in two independent population-based cohorts and to derive age-specific reference intervals.

METHODS

Four thousand two hundred sixty three participants from the Study of Health in Pomerania (SHIP-0) and 4402 participants from the independent study SHIP-Trend were included. HbA1c was determined by means of high-performance liquid chromatography. Multivariable linear regression models were performed. Reference intervals for HbA1c were determined.

RESULTS

Reference intervals were derived from a healthy subpopulation with the upper reference limit (URL) for HbA1c of 42.1 mmol/Mol (6.0%) for individuals aged 20-39 years increasing to 43.2 mmol/Mol (6.1%) for individuals aged 40-59 years. For people aged ≥60 years the URL was 47.5 mmol/Mol (6.5%). In both study populations an increase in HbA1c with age was observed. ANOVA revealed up to 8.5 mmol/Mol (0.77%) or 7.3 mmol/Mol (0.68%) higher estimated mean levels of HbA1c in the oldest compared to the youngest age group in SHIP-0 or SHIP-trend, respectively. Linear regression analyses confirmed the positive associations of HbA1c with age which was independent of BMI CONCLUSION: The present study confirmed the previously observed increase of HbA1c with increasing age in non-diabetic individuals. As a consequence age-dependent reference values for HbA1c were derived from two large and well defined reference populations. Implementation of them into daily practice may improve patient care and diagnosis of diabetes and reduce the risk of misdiagnosis and subsequent overtreatment of diabetes in elderly patients.

Risk factors for the development of micro-vascular complications of type 2 diabetes in a single-centre cohort of patients

AIMS

In type 2 diabetes, we aimed at clarifying the role of glycated haemoglobin variability and other risk factors in the development of the main micro-vascular complications: peripheral neuropathy, nephropathy and retinopathy.

METHODS

In a single-centre cohort of 900 patients, glycated haemoglobin variability was evaluated as intra-individual standard deviation, adjusted standard deviation and coefficient of variation of serially measured glycated haemoglobin in the 2-year period before a randomly selected index visit. We devised four models considering different aspects of glycated haemoglobin evolution. Multivariate stepwise logistic regression analysis was performed including the following covariates at the index visit: age, disease duration, body mass index, total cholesterol, high-density lipoprotein cholesterol, triglycerides, sex, smoking habit, hypertension, dyslipidemia, treatment with anti-diabetic drugs, occurrence of macro-vascular events and the presence of another micro-vascular complication.

RESULTS

Males with high mean glycated haemoglobin, long duration of diabetes, presence of macro-vascular events and retinopathy emerged at higher risk for peripheral neuropathy. Development of nephropathy was independently associated with higher glycated haemoglobin variability, older age, male sex, current smoking status, presence of retinopathy, of peripheral neuropathy and of hypertension. Higher mean glycated haemoglobin, younger age, longer duration of diabetes, reduced estimated glomerular filtration rate and the presence of peripheral neuropathy were significantly associated with increased incidence of retinopathy.

CONCLUSION

Glycated haemoglobin variability was associated with increased incidence of nephropathy, while mean glycated haemoglobin emerged as independent risk factor for the development of retinopathy and peripheral neuropathy. The presence of macro-vascular events was positively correlated with peripheral neuropathy. Finally, the occurrence of another micro-vascular complication was found to be a stronger risk factor for developing another micro-vascular complication than the mean or variability of glycated haemoglobin.

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

BACKGROUND

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).

METHODS

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).

RESULTS

Two patients had the HbJ Bangkok variant. Hb genotypes of these patients were β^41-42 /β^{J Bangkok} and β^N /β^{J Bangkok} , and the content of HbJ Bangkok was 93.9% and 52.4%, respectively. The remaining three patients had the following: HbE (β^N /β^E Hb genotype, 23.6% HbE content), HbG Taipei (β^N /β^{G 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.

CONCLUSIONS

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.

Association of Glycated Haemoglobin and Serum Apolipoproteins with Diabetic Retinopathy: An Indian Overview

INTRODUCTION

India is presently facing an epidemic of diabetes mellitus and the risks of chronic complications from the disease are associated with the duration of the disease as well as the degree of hyperglycaemia. Diabetic retinopathy is a known microvascular complication of diabetes mellitus and is the most common cause of blindness in the western countries.Apolipoproteins are the protein component of lipoproteins. Apart from acting as structural proteins, they also act as cofactors to various enzymes.

AIM

To measure the levels of serum apolipoproteins and glycated haemoglobin in cases of diabetic retinopathy and to assess their association with the stages of diabetic retinopathy.

MATERIAL AND METHODS

The 135 diabetic cases [with (110) and without (125) retinopathy] attending the Ophthalmology OPD of this tertiary care hospital were included in the present study. Following retinoscopy, the patients were classified as Non-Proliferative Diabetic Retinopathy (NPDR) (n=75) and Proliferative Diabetic Retinopathy (PDR) (n=35). The controls (n=100) were age and sex matched patients who did not have diabetes. The cases and controls were assessed for HbA1c, total cholesterol, triglycerides, HDL cholesterol, Apo A-I and Apo B-100.

RESULTS

The HbA1c was found to be higher in diabetics without retinopathy (7.02%) as compared to controls (5.58%) (p<0.05) and the highest value was seen in the mild NPDR group (8.82%). The mean value of Apo A-I was found to be lowest in the diabetics without retinopathy at 88 mg/dl and the highest in severe NPDR at 167 mg/dL. The mean value of Apo B-100 was found to be highest in severe NPDR at 114 mg/dL. The mean value of HDL cholesterol was lowest in moderate NPDR at 36.6 mg/dl. Total cholesterol was highest in severe NPDR at 280.88mg/dl while triglyceride was highest in severe NPDR at 286.4mg/dl.

CONCLUSION

In our study, the level of HbA1c was found to range from 5.58% in non-diabetic to 8.82% in mild NPDR. There was a clear association between Apo B-100 and total cholesterol, triglycerides with the highest value of each parameter seen in the severe NPDR group. There was a discordance noted in the levels of HDL and Apo A-I in various groups. Apo B-100 values may be of value in prognosis of diabetic retinopathy as higher values may result in progression of the disease. Further studies involving Lp(a) and homocysteine may be required in cases of diabetic retinopathy.

Evaluation of hemoglobin A1c measurement from filter paper using high-performance liquid chromatography and immunoturbidimetric assay

Glycated hemoglobin (HbA_1c) measurement from whole blood (WB) samples is inconvenient for epidemic surveillance and self-monitoring of glycemic level. We evaluated HbA_1c measurement from WB blotted on filter paper (FP), which can be easily transported to central laboratories, with high-performance liquid chromatography (HPLC) and immunoturbidimetric assay (ITA). WB was applied to Whatman filter paper. By using HPLC and WB samples as reference methods, these FP samples were evaluated on HPLC and ITA. Inter- and intra-assay variation, WB vs. FP agreement and sample stability at 20-25 °C and -70 °C were assessed by statistical analysis. Results showed that the coefficient of variation (CV, %) of FP samples for HPLC and ITA were 0.44-1.02% and 1.47-2.72%, respectively (intra-assay); 2.13-3.56% and 3.21-4.82%, respectively (inter-assay). The correlation of WB HPLC with FP analyzed using HPLC and ITA are both significant (p < 0.001). Sample stability showed that FP method up to 5 days at 20-25 °C and 5 weeks at -70 °C is accurate and reproducible. In conclusion, FP samples analyzed by HPLC and ITA can both provide an alternative to WB for HbA_1c measurement, supporting the use of FP method in epidemic surveillance and healthcare units.