The clinical use of hemoglobin A1c

Impact of glycemic control on colonoscopy outcomes: bowel preparation and polyp detection

Background

The negative effect of diabetes mellitus (DM) on the colonoscopy preparation has been previously established. Metabolic syndrome has been shown to increase risk for malignancy and possibly for premalignant lesions. This study aimed to investigate the impact of DM control on colonoscopy outcomes including bowel preparation and adenoma detection rate (ADR).

Methods

We included patients with DM who underwent colonoscopy in our hospital and had a documented glycated hemoglobin (HbA1C) within 3 months. Patients were categorized into three groups based on their HbA1C level. The clinical and endoscopic data were collected and analyzed.

Results

Our cohort included 352 DM patients. The mean age was 63.5 years. When patients were analyzed based on HBA1C, bowel preparation was poor in 46.7% of patients with good glycemic control, 52.1% of patients with fair control and 50% of patients with poor control. ADR was 24.3% in patients with good glycemic control, 20.2% in patients with fair glycemic control and 27.1% in patients with poor glycemic control. There was no statistically significant difference in the quality of preparation or adenoma detection amongst the groups.

Conclusion

The degree of glycemic control did not impact the quality of bowel preparation or ADR.

No association between glucose at age 30 and aortic diameter at age 65 in men: a population-based study

OBJECTIVES

Impaired glucose metabolism and diabetes mellitus has been linked to a decreased risk for abdominal aortic aneurysm development in men. We evaluated potential relationships between blood glucose levels in 1722 men with mean age 34 years and their aortic diameter measured by ultrasound at age 65 years.

DESIGN

Prospective cohort study.

RESULTS

Mean follow-up between baseline glucose investigation and aortic ultrasound was 32.8 ± 1.8 years. There was no correlation between baseline blood glucose and later aortic diameter (r = 0.035, p = 0.146), whereas a weak correlation between body mass index (BMI) and aortic diameter was observed (r = 0.097 p < 0.001). In a partial correlation between aortic diameter and glucose levels adjusted for BMI, the correlation did not change (r = 0.011, p = 0.66). Neither were there any significant differences in mean aortic diameter between men belonging to different quartiles of baseline blood glucose levels (19.5, 19.1, 19.6 and 19.7 mm, p = 0.18).

CONCLUSION

Fasting blood glucose in 33-year-old men was not associated with their aortic diameter at age 65 years. Potential pathophysiological processes linking disturbed glucose metabolism to a decreased risk for development of abdominal aortic aneurysm in men are therefore probably not relevant until later in life.

Eight Weeks of Cosmos caudatus (Ulam Raja) Supplementation Improves Glycemic Status in Patients with Type 2 Diabetes: A Randomized Controlled Trial

Objectives. Optimizing glycemic control is crucial to prevent type 2 diabetes related complications. Cosmos caudatus is reported to have promising effect in improving plasma blood glucose in an animal model. However, its impact on human remains ambiguous. This study was carried out to evaluate the effectiveness of C. caudatus on glycemic status in patients with type 2 diabetes. Materials and Methods. In this randomized controlled trial with two-arm parallel-group design, a total of 101 subjects with type 2 diabetes were randomly allocated to diabetic-ulam or diabetic controls for eight weeks. Subjects in diabetic-ulam group consumed 15 g of C. caudatus daily for eight weeks while diabetic controls abstained from taking C. caudatus. Both groups received the standard lifestyle advice. Results. After 8 weeks of supplementation, C. caudatus significantly reduced serum insulin (-1.16 versus +3.91), reduced HOMA-IR (-1.09 versus +1.34), and increased QUICKI (+0.05 versus -0.03) in diabetic-ulam group compared with the diabetic controls. HbA1C level was improved although it is not statistically significant (-0.76% versus -0.37%). C. caudatus was safe to consume. Conclusions. C. caudatus supplementation significantly improves insulin resistance and insulin sensitivity in patients with type 2 diabetes.

Rational diagnoses of diabetes: the comparison of 1,5-anhydroglucitol with other glycemic markers

Diabetes mellitus (DM) is a frequently encountered disease with important morbidity and mortality. The aim of this study is to document the importance of 1,5-anhydroglucitol (1,5-AG) for the diagnosis of prediabetes and DM, as well as to compare the 1,5-AG with other glycemic markers in order to understand which one is the better diagnostic tool. Between April 2012 and December 2012, 128 participants enrolled in the study. Participants were split into five groups that are IFG, IGT, IFG+IGT, diabetic and control groups by their OGTT results. The diagnostic value of markers was compared by ROC (receiver operating characteristic) method. The mean serum 1,5-AG levels in the diabetic group (33.38 nmol/ml) were lower than, IFG (59.83 nmol/ml), IGT (54.44 nmol/ml), IFG+IGT (51.98 nmol/ml) and control groups (73.24 nmol/ml). When analyzed in the total study population serum 1,5-AG levels did not differ by gender significantly. When analyzed in the total study population, 1,5-AG correlates inversely with age significantly (p = 0.036). In subgroup analysis, in the control group, serum 1,5-AG level was also inversely correlated with age (p = 0.087). The best marker for the diagnosis of prediabetes and DM was fasting plasma glucose (FPG). 1,5-AG was not found to be effective for the diagnosis of DM. This study, contributes to our knowledge of the efficiency and cut-off values of 1,5-AG for the diagnosis of prediabetes and DM. In future, there is a need for larger studies with more standardized and commonly used measurement methods for 1,5-AG, in order to evaluate the efficiency of 1,5-AG for the diagnosis of prediabetes and DM.

Effect of iron deficiency anaemia on HbA1c levels is dependent on the degree of anaemia

OBJECTIVES

Studies suggest that iron deficiency anaemia (IDA) is associated with higher HbA1c levels. We conducted a control–case study to investigate the effect of IDA on HbA1c levels, measured by two commonly used methods, in non-diabetic individuals.

DESIGN AND METHODS

A total of 122 patients were included, 61 patients with IDA and 61 patients without anaemia. HbA1c was measured by both ion exchange HPLC Variant II Turbo BioRad and immunoturbidimetry (IT) Tina Quant II Roche Diagnostics in each sample. HbA1c results were compared between groups. For correlation analysis, patients were considered altogether.

RESULTS

There was a significant difference between the results of HbA1c in patients with IDA [HPLC 5.6 ± 0.4% (38 ± 4.4 mmol/mol) and IT 5.7 ± 0.4% (39 ± 4.4 mmol/mol)] and those measured in patients without anaemia [HPLC 5.3 ± 0.4% (34 ± 4.4 mmol/mol) and IT 5.3 ± 0.3% (34 ± 3.3 mmol/mol)], (p < 0.001). Significant negative correlations were observed between total haemoglobin (Hb), haematocrit, mean corpuscular volume (MCV) and ferritin with HbA1c values measured by IT (r = − 0.557; r = − 0.539; r = − 0.488; r = − 0.499; p < 0.01; respectively). These negative correlations were weaker with HbA1c measured by HPLC (r = − 0.272; r = − 0.250; r = − 0.273; r = − 0.229 for Hb, haematocrit, MCV and ferritin; p < 0.05; respectively). HbA1c results were higher in patients with moderate and severe anaemia. However mild anaemia did not show significant effects on HbA1c results measured by both methods.

CONCLUSIONS

IDA affects HbA1c results and this effect is dependent on anaemia degree. These upward changes are statistically significant but they may be not clinically relevant when the overall variability of the HbA1c test is considered. The presence of slight anaemia is likely to have a minor effect on HbA1c levels favouring its use to diagnose diabetes in patients with mild anaemia.

Metabolic parameters in type 2 diabetic patients with varying degrees of glycemic control during Ramadan: An observational study

AIMS/INTRODUCTION

The changes in metabolic parameters in type 2 diabetic patients who fast during Ramadan have not been studied in Singapore. This study aimed to examine the trends of glycated hemoglobin (HbA1c), systolic blood pressure, low-density lipoprotein cholesterol, and triglycerides in diabetic patients with varying degrees of glycemic control and different types of therapeutic approaches during Ramadan.

METHODS

The present retrospective study used a national electronic database to examine the metabolic parameter of Malay patients with type 2 diabetes. Eligible patients were stratified into three groups based on their mean HbA1c control before Ramadan: group 1 (HbA1c ≥10%), group 2 (HbA1c 7.1-9.9%) and group 3 (HbA1c ≤7%). Patients with a glomerular filtration rate <15 mL/min were excluded. The trends of metabolic parameters were traced before, during and after Ramadan.

RESULTS

Of 13,565 patients examined, 5,172 patients (38.1%) were eligible for this study. Mean change of HbA1c varied from -1.4% to +0.2% during Ramadan, with the greatest reduction observed in group 1 (P < 0.001). A minimal systolic blood pressure reduction was observed in groups 2 and 3 (2 mmHg; P < 0.01). Low-density lipoprotein cholesterol and triglycerides changes were insignificant. A small, 0.1%, reduction in mean HbA1c was observed in patients taking oral antidiabetic agents during Ramadan (P < 0.001).

CONCLUSIONS

Blood glucose was most affected during Ramadan, particularly in patients with mean baseline HbA1c ≥10%. The type of antidiabetic agent used did not seem to contribute to glycemic changes.

The Benefit of a Glucose-Sparing PD Therapy on Glycemic Control Measured by Serum Fructosamine in Diabetic Patients in a Randomized, Controlled Trial (IMPENDIA)

BACKGROUND/AIMS

Poor glycemic control can lead to increased morbidity and mortality in peritoneal dialysis (PD) patients. Serum fructosamine may be a more reliable marker of glycemic control than HbA1c in dialysis patients.

METHODS

We evaluated the effects of a glucose-sparing PD regimen on serum fructosamine. In the multicenter, controlled IMPENDIA trial, eligible diabetic PD patients were randomized (1:1) to a 24-hour combination of a glucose sparing regimen (n = 89) or a glucose-based therapy (n = 91). Serum fructosamine and HbA1c were measured at baseline, 3 months and 6 months; fructosamine measurements were corrected for serum albumin (AlbF).

RESULTS

Serum fructosamine decreased from 297 to 253 µmol/l in the glucose-sparing group (95% confidence interval [CI] for the difference, -26 to -68, p < 0.001), and increased from 311 to 314 µmol/l in the glucose-only group (95% CI for the difference, -23 to +19, p = 0.87). The mean difference in change of fructosamine levels between groups at 6 months was 64 µmol/l (95% CI 29-99, p < 0.001). HbA1c decreased versus baseline in both groups (treatment difference 0.3%, p = 0.07). The correlation between AlbF and baseline fasting serum glucose was stronger than that seen between HbA1c and baseline fasting serum glucose (r = 0.47, p < 0.0001 and r = 0.31, p < 0.0001, respectively).

CONCLUSION

A glucose-sparing regimen (P-E-N) improved glycemic control as measured by serum fructosamine. Further studies are needed to establish fructosamine targets that will reduce the morbidity risk related to hyperglycemia in PD patients.

Pitfalls in hemoglobin A1c measurement: when results may be misleading

Since the beginning of clinical use in the 1970s, hemoglobin A1c (A1c) has become the standard tool for monitoring glycemic control in patients with diabetes. The role of the A1c test was broadened in 2010, when the American Diabetes Association added A1c as a diagnostic criterion for diabetes. Because of hemoglobin A1c's integral role in diagnosis and treatment, it is important to recognize clinical scenarios and interfering factors that yield false results. The purpose of this review is to describe the A1c measurement, outline clinical scenarios or factors that may yield false results, and describe alternative laboratory biomarkers.

Current concepts in blood glucose monitoring

Blood glucose monitoring has evolved over the last century. The concept of adequate glycemic control and minimum glycemic variability requires an ideal, accurate and reliable glucose monitoring system. The search for an ideal blood glucose monitoring system still continues. This review explains the various blood glucose monitoring systems with special focus on the monitoring systems like self- monitored blood glucose (SMBG) and continuous glucose monitoring system (CGMS). It also focuses on the newer concepts of blood glucose monitoring and their incorporation in routine clinical management of diabetes mellitus.

Supplementation with 1% energy trans fatty acids had little effect on serum cholesterol levels in healthy young Japanese women

The World Health Organization (WHO) has recommended that trans fatty acid (TFA) intake should be less than 1% of total energy intake, but few data are available as to the influence of energy TFA intake of as low as 1% on blood cholesterol levels. A randomized, double-blind, parallel trial was conducted to assess the effects of 1% TFA dietary supplementation on serum cholesterol levels in healthy young women. Sixty-five volunteers consumed cookies containing 1% (TFA) or 0.04% (control) energy of TFA for 4 weeks and blood was harvested after overnight fasting. There were no significant differences in serum LDL- or HDL-cholesterol levels between the two groups. The hemoglobin A1c level was not influenced by dietary TFA. These results suggest that energy of TFAs at less than 1% has little effect on serum cholesterol or hemoglobin A1c levels in healthy young women. This confirms the correctness of the WHO recommendation.

Managing laboratory test ordering through test frequency filtering

Modern computer systems allow limits to be set on the periods allowed for repetitive testing. We investigated a computerised system for managing potentially overtly frequent laboratory testing, calculating the financial savings obtained.

In consultation with hospital physicians, tests were selected for which ‘spare periods’ (periods during which tests are barred) might be set to control repetitive testing. The tests were selected and spare periods determined based on known analyte variations in health and disease, variety of tissues or cells giving rise to analytes, clinical conditions and rate of change determining analyte levels, frequency with which doctors need information about the analytes and the logistical needs of the clinic.

The operation and acceptance of the system was explored with 23 analytes. Frequency filtering was subsequently introduced for 44 tests, each with their own spare periods. The proportion of tests barred was 0.56%, the most frequent of these being for total cholesterol, uric acid and HDL-cholesterol. The financial savings were 0.33% of the costs of all testing, with HbA

Managing laboratory testing through computerised limits to prevent overtly frequent testing is feasible. The savings were relatively low, but sustaining the system takes little effort, giving little reason not to apply it. The findings will serve as a basis for improving the system and may guide others in introducing similar systems.

Assessment of carotid atherosclerosis in type 2 diabetes mellitus patients with microalbuminuria by high-frequency ultrasonography

The aim of this study is to evaluate carotid atherosclerosis in patients of type 2 diabetes mellitus with microalbuminuria (MA) by high-frequency ultrasonography. Two hundred and fifty patients of type 2 diabetes mellitus were divided into two groups according to urinary albumin excretion rate (UAER): normoalbuminuria group (130 cases) and microalbuminuria group (120 cases). The intimal-medial thickness (IMT) and the atherosclerotic plaques of carotid artery were observed in both groups by high-frequency ultrasound. Fasting blood glucose (FBG), hemoglobin A1c, and lipid profiles were measured. The values of IMT of microalbuminuria group were significantly higher than those of normoalbuminuria group (P < 0.05). In univariate analysis, IMT was positively and significantly associated with age (r = 0.265, P < 0.05), waist circumference (r = 0.263, P < 0.05), body mass index (r = 0.285, P < 0.05), systolic blood pressure (r = 0.276, P < 0.05), UAER (r = 0.359, P < 0.05), HbA1c (r = 0.462, P < 0.05) and, duration of diabetes (r = 0.370, P < 0.05). In multivariate linear regression analysis, UAER and HbA1c were independent predictors of IMT (P < 0.05 for all). In the two groups, the rate of soft plaques was higher than that of dense plaques and calcified plaques. In conclusion, there is a significant association between microalbuminuria and IMT which is regarded as the early sign of carotid atherosclerosis in type 2 diabetic patients.

Alternative markers of hyperglycemia and risk of diabetes

OBJECTIVE

Fructosamine, glycated albumin, and 1,5-anhydroglucitol (1,5-AG) are of interest for monitoring short-term glycemic control in patients with diabetes; however, their associations with diabetes risk are uncharacterized.

RESEARCH DESIGN AND METHODS

We used Cox proportional hazards models to examine the associations of fructosamine, glycated albumin, and 1,5-AG with incident diabetes in 1,299 participants, from the Atherosclerosis Risk in Communities (ARIC) Study (2005-2006), who had no history of diagnosed diabetes at baseline. Incident diabetes was self-reported during annual telephone calls.

RESULTS

There were 119 new cases of diabetes during a median follow-up of 3.3 years. When compared with the lowest quartile, the fourth quartiles of fructosamine and glycated albumin were significantly associated with diabetes risk (hazard ratio [HR] 3.99 [95% CI 1.93-8.28] and 5.22 [2.49-10.94], respectively). The fourth quartile of 1,5-AG was associated with a significantly lower diabetes risk (0.27 [0.14-0.55]). Associations were attenuated but still significant after adjustment for hemoglobin A(1c) (A1C) or fasting glucose.

CONCLUSIONS

Fructosamine, glycated albumin, and 1,5-AG were associated with the subsequent development of diabetes independently of baseline A1C and fasting glucose. Our results suggest these alternative biomarkers may be useful in identifying persons at risk for diabetes.

Mass spectrometry-based protein assays for in vitro diagnostic testing

Mass spectrometry-based protein assays hold great promise for in vitro diagnostic testing. Technological advances in mass spectrometry have given rise to instruments and methods that are fully capable of automated and high-throughput protein assaying. Yet, the numerous steps involved in such assays can lead to difficulties in assay characterization and validation, and can also make them unnecessarily complex and prohibitively expensive for everyday use. Simplification of both approaches and instrumentation seems to be the solution to the fast introduction of the mass spectrometry-based assays into the clinical laboratories. One such simplified approach is the mass spectrometric immunoassay, which couples targeted immunoaffinity protein separation with the power of mass spectrometry detection. Several mass spectrometric immunoassays have been extensively characterized and have found their way into clinical laboratory improvement amendments-certified laboratories in the form of laboratory developed tests. Reviewed in this special report is the development and validation of one of those assays - a Cystatin mass spectrometric immunoassay. With the added advantage of protein variant detection and quantification, these assays can redefine our view of protein diversity, with clear implications in biomarker discovery, validation, and ultimately, in vitro diagnostic testing.

Optimal energy distribution of carbohydrate intake for Japanese elderly patients with type 2 diabetes: the Japanese Elderly Intervention Trial

AIM

In diet therapy for diabetes, optimal energy intake and the energy distribution of macronutrients (protein : fat : carbohydrate [PFC] energy ratio) are important. We aimed to clarify the correlation between the PFC energy ratio and metabolic parameters including glycated hemoglobin A1c (HbA1c) and triglycerides in Japanese elderly patients with type 2 diabetes mellitus aged 65 years or older.

METHODS

Participants were 1173 diabetic patients aged 65 years or older with serum HbA1c level of >/=7.4% enrolled in the Japanese Elderly Diabetes Intervention Trial (J-EDIT). The participants were divided into four groups by the percentage of total energy intake (%E) of carbohydrate (C1: less than 55%E, C2: 55%E or more and less than 60%E, C3: 60%E or more and less than 65%E, and C4: 65%E or more). Relations of %E of carbohydrate to HbA1c and other metabolic parameters, energy intake and nutritional intake were examined. Furthermore, the subjects were divided into four categories by HbA1c levels by quartile method (Q1: less than 7.90%, Q2: 7.90% or more and less than 8.30%, Q3: 8.30% or more and less than 8.80%, Q4: 8.80% or more). Relations of HbA1c to other metabolic parameters, energy intake and nutritional intake were examined.

RESULTS

The mean HbA1c levels in the four groups were C1: 8.40%, C2: 8.50%, C3: 8.41% and C4: 8.36% in men, and C1: 8.51%, C2: 8.47%, C3: 8.35% and C4: 8.52% in women, respectively. There were no significant differences and linear trend in HbA1c levels across groups. The mean triglyceride levels were in the range of 122-128 mg/dL in men from C1 to C3, although it was significantly higher in C4 (177 mg/dL). The mean triglyceride levels were in the range of 128-136 mg/dL in women from C1 to C3, although it was significantly higher in Q4 (150 mg/dL). Amounts of protein and fat intakes decreased with an increase of %E of carbohydrate, although amount of carbohydrate intake did not change significantly. As a result, %E of protein and fat, and energy intake decreased in both men and women with an increase in %E of carbohydrate. Among the four quartiles divided by HbA1c levels, there were no significant differences in energy intake and PFC energy ratio.

CONCLUSIONS

The present study suggests that, within the range studied, the carbohydrate energy ratio has no correlation with HbA1c levels. However, serum triglyceride levels increased and high-density lipoprotein cholesterol levels decreased significantly, with an increase of %E of carbohydrate in men, and the same tendencies were observed in women. Furthermore, in patients with 65%E or more of carbohydrate, serum triglyceride levels exceeded 150 mg/dL, which is the recommended treatment target for diabetic patients. These results suggest that the ideal %E of carbohydrate for Japanese elderly type 2 diabetes is less than 65. The lower limit of %E of carbohydrate could not be determined from the present study.

Assessment of carotid arterial wall elasticity in type 2 diabetes mellitus patients with microalbuminuria by real-time ultrasound elastography

The aim of this study was to evaluate carotid arterial wall elasticity in type 2 diabetes mellitus (T2DM) with microalbuminuria by real-time ultrasound elastography. Two hundred and ten T2DM patients were divided into two groups according to levels of urinary albumin excretion (UAE): T2DM without microalbuminuria (T2DM1 group, 120) and T2DM with microalbuminuria (T2DM2 group, 90). The right common carotid arteries were examined by real-time ultrasound elastography. The strain ratio (SR, blood to arterial wall strain ratio) was calculated by dividing the strain value of the blood by that of the carotid arterial wall. The correlation between SR and general data was analyzed. The mean SR value ± SD of T2DM2 group was significantly higher than that of T2DM1 group (P < 0.05). SR was positively and significantly correlated with UAE, HbA1c, and systolic blood pressure (r = 0.456,0.435,0.235, P < 0.05 for all). The mean value ± SD of UAE, HbA1c, 2hPG, BMI, and TC of T2DM2 group was significantly higher than that of T2DM1 group (P < 0.05 for all). In conclusion, there is an association between microalbuminuria and carotid arterial wall elasticity in T2DM patients.

Hemoglobin A1c as a measure of disease severity and outcome in limb threatening ischemia

BACKGROUND

Diabetes mellitus is a known risk factor in the development of peripheral vascular disease. Hemoglobin A1c (HbA1c) has been used by clinicians as a means to measure short to intermediate term glucose control in diabetics. Trials evaluating tight glucose control using HbA1c measurements have recently been conducted for several medical conditions. The goal of this study is to determine if the level of hemoglobin A1c has any effect on disease severity in diabetic patients with limb threatening ischemia.

METHODS

A retrospective review of all patients presenting with limb threatening ischemia between January 1 and December 31, 2007 was conducted. All patients underwent conventional arteriography prior to intervention. Of 148 patients, 73 were diabetics with a hemoglobin A1c level performed within 3 mo of presentation. Patients were placed into high (>7) and low (<7) hemoglobin A1c groups and data was collected on type of presentation, comorbidities, anatomic level of disease, tibial artery patency, need for amputation, contralateral disease, need for an open versus an endovascular procedure, and freedom from intervention. Fisher's exact t-test was used to compare the two groups. A P value <0.05 was considered statistically significant.

RESULTS

Thirty-six patients had HbA1c levels above 7.0 and 37 had levels below 7.0 (mean 7.64 ± 2.04, range 5.1-14.7). There were no statistically significant differences in the two groups in comorbities, average age, initial gangrene at presentation, aspirin or statin use, or smoking status. Patients in the high group were more likely to have had a previous attempt at revascularization (23 versus 11, P = 0.0049). There was no difference in the presence of contralateral disease (7 versus 4, P = 0.3447) or in the number of patent tibial vessels. Patients with low HbA1c levels were more likely to have the peroneal artery affected (17 versus 8, P = 0.048). In addition, TASC II classifications of iliac and femoral popliteal disease was similar between the two groups. Freedom from intervention is depicted graphically by life table analysis.

CONCLUSION

Glucose control measured by hemoglobin A1c does not appear to affect severity of disease or need for reintervention in diabetics with limb threatening ischemia. This suggests other factors related to diabetes may play a role in peripheral vascular disease. Larger, prospective studies are needed to assess the affect of glucose control in limb threatening ischemia.

Targeted quantitative mass spectrometric immunoassay for human protein variants

BACKGROUND

Post-translational modifications and genetic variations give rise to protein variants that significantly increase the complexity of the human proteome. Modified proteins also play an important role in biological processes. While sandwich immunoassays are routinely used to determine protein concentrations, they are oblivious to protein variants that may serve as biomarkers with better sensitivity and specificity than their wild-type proteins. Mass spectrometry, coupled to immunoaffinity separations, can provide an efficient mean for simultaneous detection and quantification of protein variants.

RESULTS

Presented here is a mass spectrometric immunoassay method for targeted quantitative proteomics analysis of protein modifications. Cystatin C, a cysteine proteinase inhibitor and a potential marker for several pathological processes, was used as a target analyte. An internal reference standard was incorporated into the assay, serving as a normalization point for cystatin C quantification. The precision, linearity, and recovery characteristics of the assay were established. The new assay was also benchmarked against existing cystatin C ELISA. In application, the assay was utilized to determine the individual concentration of several cystatin C variants across a cohort of samples, demonstrating the ability to fully quantify individual forms of post-translationally modified proteins.

CONCLUSIONS

The mass spectrometric immunoassays can find use in quantifying specific protein modifications, either as a part of a specific protein biomarker discovery/rediscovery effort to delineate the role of these variants in the onset of the disease, progression, and response to therapy, or in a more systematic study to delineate and understand human protein diversity.

Mass spectrometric immunoassay for quantitative determination of protein biomarker isoforms

Protein biomarkers are essential in assessing pathogenic processes. The impetus for finding new biomarkers has been accelerated by the arrival of the "omics" technologies. However, equally important is the rediscovery of existing biomarkers with these new approaches as novel variants can be discovered that can improve their utility. Presented here is a mass spectrometric immunoassay method for quantitative determination of β-2-microglobulin, an established biomarker used in the diagnosis of active rheumatoid arthritis and kidney disease, and its structural variant, cleaved at and deficient in lysine-58 (ΔK58-b2m). β-Lactoglobulin was incorporated into the assay as an internal reference standard, serving as normalization point for β-2-microglobulin quantification. The precision, linearity, and recovery characteristics of the assay were established. The new assay was also benchmarked against existing β-2-microglobulin ELISA. The assay was utilized to determine the individual concentration of β-2-microglobulin and its variant across a larger cohort of samples, demonstrating the ability to simultaneously quantify both proteins.

Evaluation of an over-the-counter glycated hemoglobin (A1C) test kit

BACKGROUND

Glycated hemoglobin (A1C) monitoring is an integral component of diabetes management. This study was conducted to evaluate the performance of the A1CNow® SELFCHECK device when used by lay users and health care professionals (HCPs) to measure A1C.

METHODS

Subjects performed two A1CNow SELFCHECK finger-stick self-tests followed by a finger-stick test of the subject's blood by a HCP. The primary endpoint assessed accuracy of the subject and HCP A1CNow SELFCHECK readings. Secondary endpoints included precision, comprehension of instructional material (written material±DVD), and product satisfaction. For accuracy comparison, a venous blood sample was drawn from each subject and tested by laboratory (TOSOH) analysis. Subject comprehension of product instructional material was evaluated via first-time failure (FTF) rate as recorded by the HCP, and subject satisfaction was assessed through written survey.

RESULTS

A total of 110 subjects with (n=93) and without (n=17) diabetes participated. Of 177 subject A1C values, 165 (93.2%) were within the acceptable range of ±13.5% of the laboratory reference value and considered accurate. Regression analysis showed good correlation of subject values to laboratory and HCP results (R2=0.93 for both). The average within-subject coefficient of variation was 4.57% (n=74). The FTF rates with and without instructional DVD were 11.3% (n=56) and 39.6% (n=54), respectively. Subjects with diabetes/prediabetes overwhelmingly indicated that they were "very" to "extremely" likely (93.5%) to discuss their home A1C results with their HCP.

CONCLUSIONS

Lay users found the A1CNow SELFCHECK easy to use, and both lay users and HCPs were able to measure A1C accurately.