Comparator Data Characteristics and Testing Procedures for the Clinical Performance Evaluation of Continuous Glucose Monitoring Systems

Comparing the performance of different continuous glucose monitoring (CGM) systems is challenging due to the lack of comprehensive guidelines for clinical study design. In particular, the absence of concise requirements for the distribution of comparator (reference) blood glucose (BG) concentrations and their rate of change (RoC) that are used to evaluate CGM performance, impairs comparability. For this article, several experts in the field of CGM performance testing have collaborated to propose characteristics of the distribution of comparator measurements that should be collected during CGM performance testing. Specifically, it is proposed that at least 7.5% of comparator BG concentrations are <70 mg/dL (3.9 mmol/L) and >300 mg/dL (16.7 mmol/L), respectively, and that at least 7.5% of BG-RoC combinations indicate fast BG changes with impending hypo- or hyperglycemia, respectively. These proposed characteristics of the comparator data can facilitate the harmonization of testing conditions across different studies and CGM systems and ensure that the most relevant scenarios representing real-life situations are established during performance testing. In addition, a study protocol and testing procedure for the manipulation of glucose levels are suggested that enable the collection of comparator data with these characteristics. This work is an important step toward establishing a future standard for the performance evaluation of CGM systems.

Glucose measurements with accu check inform II versus hexokinase plasma method during surgery under general anesthesia, an observational cohort study

PURPOSE

Limited research exists on translation of in-vitro glucose measurement interfering compounds to the in-vivo situation. We investigated whether Point-of-Care glucose measurements by Accu Chek Inform II (ACI II) were accurate to monitor glucose concentrations during surgery with general anesthesia by comparing with the reference laboratory hexokinase plasma glucose test.

METHOD

Patients undergoing surgery with general anesthesia were included. Anesthesia was maintained with either Sevoflurane or Total intravenous anesthesia (TIVA). Prior to and after induction, blood glucose was measured with ACI II and the hexokinase test. Bland-Altman analysis was performed to assess method agreement. Subgroup analyses on glucose measurement differences per type of maintenance anesthesia were performed.

RESULTS

Thirty-nine patients were included, and 78 measurements were performed. All paired measurements had clinically acceptable agreement with a percentage error of 10.0% (95% CI 8.0 to 11.9). The mean difference (95% limits of agreement) between ACI II and hexokinase for all measurements was 0.0 mmol/L (-0.7 to 0.7 mmol/L). Before induction (n = 39), mean difference was -0.1 mmol/L (-0.6 to 0.4 mmol/L), and after induction (n = 39), mean difference was 0.1 mmol/L (-0.8 to 0.9 mmol/L). Further investigation showed the difference varied per test for patients receiving Sevoflurane compared to patients receiving TIVA (-0.2 ± 0.4 mmol/L vs. 0.4 ± 0.3 mmol/L, p < 0.001). Before and after induction, the difference between ACI II and hexokinase measurements increased for patients receiving Sevoflurane compared to patients receiving TIVA (0.4 ± 0.4 mmol/L vs. -0.4 ± 0.3 mmol/L, p < 0.001).

CONCLUSION

The agreement between glucose measurements using ACI II and the reference laboratory hexokinase test was clinically acceptable with a percentage error of 10.0% (95% CI 8.0 to 11.9). The use of TIVA may negatively affect the measurement performance of the ACI II.

Clinical Performance Evaluation of Continuous Glucose Monitoring Systems: A Scoping Review and Recommendations for Reporting

The use of different approaches for design and results presentation of studies for the clinical performance evaluation of continuous glucose monitoring (CGM) systems has long been recognized as a major challenge in comparing their results. However, a comprehensive characterization of the variability in study designs is currently unavailable. This article presents a scoping review of clinical CGM performance evaluations published between 2002 and 2022. Specifically, this review quantifies the prevalence of numerous options associated with various aspects of study design, including subject population, comparator (reference) method selection, testing procedures, and statistical accuracy evaluation. We found that there is a large variability in nearly all of those aspects and, in particular, in the characteristics of the comparator measurements. Furthermore, these characteristics as well as other crucial aspects of study design are often not reported in sufficient detail to allow an informed interpretation of study results. We therefore provide recommendations for reporting the general study design, CGM system use, comparator measurement approach, testing procedures, and data analysis/statistical performance evaluation. Additionally, this review aims to serve as a foundation for the development of a standardized CGM performance evaluation procedure, thereby supporting the goals and objectives of the Working Group on CGM established by the Scientific Division of the International Federation of Clinical Chemistry and Laboratory Medicine.

Consequences of different cut-off values for high-sensitivity cardiac troponin for risk stratification of patients suspected for NSTE-ACS with a modified HEART score

Aim: This study aims to enhance prehospital risk assessment for suspected non-ST-elevation acute coronary syndrome (NSTE-ACS) patients using the HEART-score. By incorporating novel point-of-care high-sensitivity cardiac troponin devices, a modified HEART-score was developed and compared with the conventional approach. Patients & methods: Troponin points within the modified HEART-score are based on values below the limit of quantitation (LoQ), between the LoQ and 99th percentile and above the 99th percentile of the used device. A total HEART-score of three or lower is considered low-risk for major adverse cardiac events. Results & conclusion: The number of low-risk patients decreased based on the modified HEART-score. The sensitivity and negative predictive value increased which suggests increasing safety in ruling out patients with suspected NSTE-ACS.

Referral decisions based on a pre-hospital HEART score in suspected non-ST-elevation acute coronary syndrome: final results of the FamouS Triage study

Aims

Although pre-hospital risk stratification of patients with suspected non-ST-elevation acute coronary syndrome (NSTE-ACS) by ambulance paramedics is feasible, it has not been investigated in daily practice whether referral decisions based on this risk stratification is safe and does not increase major adverse cardiac events (MACE). In Phase III of the FamouS Triage study, it was investigated whether referral decisions by ambulance paramedics based on a pre-hospital HEART score, is non-inferior to routine management.

Methods and results

FamouS Triage Phase III is a non-inferiority study, comparing the occurrence of MACE before (Phase II) and after (Phase III) implementation of referral decisions based on a pre-hospital HEART score. In Phase II, all patients were risk-stratified and referred to the hospital; in Phase III, low-risk patients (HEART score ≤ 3) were not referred. Primary endpoint was MACE (acute coronary syndrome, revascularization, or death) within 45 days. A total of 1236 patients were included. Mean age was 63 years, 43% were female, 700 patients were included in the second phase and 536 in the third phase in which 149 low-risk patients (28%) were not transferred to the hospital. Occurrence of 45 days MACE was 16.6% in Phase II and 15.7% in Phase III (P = 0.67). Percentage MACE in low-risk patients was 2.9% in Phase II and 1.3% in Phase III. After adjustments for differences in baseline variables, the hazard ratio of 45 days MACE in Phase III was 0.88 (95% confidence interval 0.63–1.25) as compared to Phase II.

Conclusion

Pre-hospital risk stratification of patients with suspected NSTE-ACS, avoiding hospitalization of a substantial number of low-risk patients, seems feasible and non-inferior to transferring all patients to the hospital.

Referral decisions based on a pre-hospital HEART score in suspected non-ST-elevation acute coronary syndrome: final results of the Famous Triage study

Background

Recent studies show that pre-hospital risk stratification of patients with suspected non-ST-elevation Acute Coronary Syndrome (NSTE-ACS) by ambulance paramedics is feasible. However, it is not investigated whether making referral decisions based on this risk stratification is safe and not associated with an increased risk of Major Adverse Cardiac Events (MACE). The hypothesis of the Famous Triage study is that implementation of referral decisions by ambulance paramedics based on a pre-hospital HEART score (History, ECG, Age, Risk factors and Troponin), is non-inferior to routine management on the occurrence of MACE within 45 days.

Methods

Famous Triage phase III is the first study where referral decisions by paramedics are based on a pre-hospital acquired HEART score. In the second phase (before implementation) a pre-hospital HEART score was assessed without consequences for referral decisions. In the third phase low-risk patients (HEART score ≤3) were not transferred to the hospital. Primary endpoint was the comparison of MACE (acute coronary syndrome, revascularization or death by all causes) within 45 days between phase II and III.

Results

A total of 1,236 patients were included, mean age was 63 years, 43% was female, 700 patients were included in the second phase (all referred to the hospital) and 536 in the third phase in which 149 low-risk patients (28%, HEART score ≤3) were not transferred to the hospital. Occurrence of 45 days MACE was 16.6% in phase II and 15.7% in phase III (p=0.67). Percentage MACE in low-risk patients was 2.9% in phase II and 1.3% in phase III. After adjustments for differences in baseline variables, the odds ratio of 45 days MACE in phase III was 0.88 (95% CI 0.63 – 1.25) as compared to phase II.

Conclusion

Pre-hospital risk stratification of patients with suspected NSTE-ACS, avoiding hospitalization of a substantial number of low-risk patients, is feasible and non-inferior to transferring all patients to the hospital. This pre-hospital triage strategy might improve value based healthcare (equal outcomes at less costs).

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Roche Diagnostics, The Netherlands

Pre-hospital versus hospital acquired HEART score for risk classification of suspected non ST-elevation acute coronary syndrome

INTRODUCTION

Although increasing evidence shows that in patients with suspected non-ST-elevation acute coronary syndrome (NSTE-ACS) both hospital and pre-hospital acquired HEART (History, ECG, Age, Risk factors, Troponin) scores have strong predictive value, pre-hospital and hospital acquired HEART scores have never been compared directly.

METHODS

In patients with suspected NSTE-ACS, the HEART score was independently prospectively assessed in the pre-hospital setting by ambulance paramedics and in the hospital by physicians. The hospital HEART score was considered the gold standard. Low-risk (HEART score ≤3) was considered a negative test. Endpoint was occurrence of major adverse events within 45 days.

RESULTS

A total of 699 patients were included in the analyses. In 516 (74%) patients pre-hospital and hospital risk classification was similar, in 50 (7%) pre-hospital risk classification was false negative (45 days mortality 0%) and in 133 (19%) false positive (45 days mortality 1.5%). False negative risk classifications were caused by differences in history (100%), risk factor assessment (66%) and troponin (18%) and were more common in older patients. Occurrence of major adverse events was comparable in pre-hospital and hospital low-risk patients (2.9% vs. 2.7%, p = 0.9). Incidence of major adverse events was 0% in the true negative group, 26% in the true positive group, 10% in the false negative group and 5% in the false positive group. Predictive value of both pre-hospital and hospital acquired HEART scores was high, although the 'area under the curve' of hospital acquired HEART score was higher (0.84 vs. 0.74, p < 0.001).

CONCLUSION

In approximately 25% of patients hospital and pre-hospital HEART score risk classifications disagree, mainly by risk overestimation in the pre-hospital group. Since disagreement is primarily caused by different scoring of history and risk factors, additional training may improve pre-hospital scoring.

Determinants of HbA1c reduction with FreeStyle Libre flash glucose monitoring (FLARE-NL 5)

Aims

To identify factors predicting HbA1c reduction in patients with diabetes mellitus (DM) using FreeStyle Libre Flash Glucose Monitoring (FSL-FGM).

Methods

Data from a 12-month prospective nation-wide FSL registry were used and analysed with multivariable regression. For the present study we included patients with hypoglycaemia unawareness or unexpected hypoglycaemias (n = 566) and persons who did not reach acceptable glycaemic control (HbA1c > 70 mmol/mol (8.5%)) (n = 294). People with other indications for use, such as sensation loss of the fingers or individuals already using FSL-FGM or rtCGM, were excluded (37%).

Results

Eight hundred and sixty persons (55% male with a mean age of 46.7 (±16.4) years) were included. Baseline HbA1c was 65.1 (±14.5) mmol/mol (8.1 ± 1.3%), 75% of the patients had type 1 DM and 37% had microvascular complications. Data concerning HbA1c was present for 482 (56.0%) at 6 months and 423 (49.2%) persons at 12 months. A significant reduction in HbA1c (≥5 mmol/mol (0.5%)) was present in 187 (22%) persons. For these persons, median HbA1c reduction was −9.0 [−13.0, −4.0] mmol/mol (−0.82 [−1.19, −0.37]%) at 6 months and −9.0 [−15.0, −7.0] mmol/mol (−0.82 [−1.37, −0.64]%) at 12 months. In multivariable regression analysis with age, gender and SF-12 physical and mental component scores as covariates, only baseline HbA1c was significant: −0.319 (SE 0.025; p < 0.001; R² = 0.240 for the model). In exploratory analysis among subgroups with different indications for FSL-FGM use (hypoglycaemia unawareness or persistently high HbA1c) and persons with a significant HbA1c decrease over the study period, baseline HbA1c remained the only significant predictor.

Conclusions

Among the variables we analysed in the present study, only high HbA1c at baseline predicts significant HbA1c reduction during FSL-CGM use.

Referral decisions based on a prehospital HEART score in suspected non-ST-elevation acute coronary syndrome: design of the FamouS Triage 3 study

Background: It is not yet investigated whether referral decisions based on prehospital risk stratification of non-ST-elevation Acute Coronary Syndrome (NSTE-ACS) by the complete History, ECG, Age, Risk factors and initial Troponin (HEART) score are feasible and safe. Hypothesis: Implementation of referral decisions based on the prehospital acquired HEART score in patients with suspected NSTE-ACS is feasible and not inferior to routine management in the occurrence of major adverse cardiac events within 45 days. Study design & methods: FamouS Triage 3 is a feasibility study with a before-after sequential design. The aim is to assess whether prehospital HEART-score management including point-of-care troponin measurement is feasible and noninferior to routine management. Primary end point is the occurrence of major adverse cardiac events within 45 days. Conclusion: If referral decisions based on prehospital acquired risk stratification are feasible and noninferior this can become the new prehospital management in suspected NSTE-ACS.

In-Hospital Healthcare Utilization, Outcomes, and Costs in Pre-Hospital-Adjudicated Low-Risk Chest-Pain Patients

BACKGROUND

There is increasing evidence that in patients presenting with acute chest pain, pre-hospital triage can accurately identify low-risk patients. It is, however, still unclear which diagnostics are performed in pre-hospital-adjudicated low-risk patients and what the contribution is of those diagnostic results in the healthcare process.

OBJECTIVES

The aim of this study was to quantify healthcare utilization, costs, and outcomes in pre-hospital-adjudicated low-risk chest-pain patients, and to extrapolate to total costs in the Netherlands.

METHODS

This was a prospective cohort study including 700 patients with suspected non-ST-elevation acute coronary syndrome in which pre-hospital risk stratification using the HEART score was performed by paramedics. Low risk was defined as a pre-hospital HEART score ≤ 3. Data on (results of) hospital diagnostics, costs, and discharge diagnosis were collected.

RESULTS

A total of 172 (25%) patients were considered as low risk. Of these low-risk patients, the mean age was 54 years, 52% were male, and 84% of patients were discharged within 12 h. Repeated electrocardiography and routine laboratory measurements, including cardiac markers, were performed in all patients. Chest X-ray was performed in 61% and echocardiography in 11% of patients. After additional diagnostics, two patients (1.2%) were diagnosed as non-ST-elevation myocardial infarction and two patients (1.2%) as unstable angina. Other diagnoses were atrial fibrillation (n = 1) and acute pancreatitis/cholecystitis (n = 2); all other patients had non-specific/non-acute discharge diagnoses. Mean in-hospital costs per patient were €1580. The estimated yearly acute healthcare cost in low-risk chest-pain patients in the Netherlands is €30,438,700.

CONCLUSION

In low-risk chest-pain patients according to pre-hospital risk assessment, acute healthcare utilization and costs are high, with limited added value. Possibly, if a complete risk assessment can be performed by ambulance paramedics, acute hospitalization of the majority of low-risk patients is not necessary, which can lead to substantial cost reduction.

TRIAL ID

Dutch Trial Register [http://www.trialregister.nl]: trial number 4205.

Impact of elevated HbA1c on long-term mortality in patients presenting with acute myocardial infarction in daily clinical practice: insights from a 'real world' prospective registry of the Zwolle Myocardial Infarction Study Group

BACKGROUND

Long-term clinical outcome is less well known in up to presentation persons unknown with diabetes mellitus who present with acute myocardial infarction and elevated glycosylated haemoglobin (HbA1c) levels on admission. We aimed to study the prognostic impact of deranged HbA1c at presentation on long-term mortality in patients not known with diabetes, presenting with acute myocardial infarction.

METHODS

A single-centre, large, prospective observational study in patients with and without known diabetes admitted to our hospital for ST-segment elevation myocardial infarction (STEMI) and non-STEMI. Newly diagnosed diabetes mellitus was defined as HbA1c of 48 mmol/l or greater and pre-diabetes mellitus was defined as HbA1c between 39 and 47 mmol/l. The primary endpoint was all-cause mortality at short (30 days) and long-term (median 52 months) follow-up.

RESULTS

Out of 7900 acute myocardial infarction patients studied, 1314 patients (17%) were known diabetes patients. Of the 6586 patients without known diabetes, 3977 (60%) had no diabetes, 2259 (34%) had pre-diabetes and 350 (5%) had newly diagnosed diabetes based on HbA1c on admission. Both short-term (3.9% vs. 7.4% vs. 6.0%, p<0.001) and long-term mortality (19% vs. 26% vs. 35%, p<0.001) for both pre-diabetes patients as well as newly diagnosed diabetes patients was poor and comparable to known diabetes patients. After multivariate analysis, newly diagnosed diabetes was independently associated with long-term mortality (hazard ratio 1.72, 95% confidence interval 1.27-2.34, P=0.001).

CONCLUSIONS

In the largest study to date, newly diagnosed or pre-diabetes was present in 33% of acute myocardial infarction patients and was associated with poor long-term clinical outcome. Newly diagnosed diabetes (HbA1c ⩾48 mmol/mol) is an independent predictor of long-term mortality. More attention to early detection of diabetic status and initiation of blood glucose-lowering treatment is necessary.

Pre-hospital risk assessment in suspected non-ST-elevation acute coronary syndrome: A prospective observational study

Background:

Pre-hospital risk stratification of non-ST-elevation acute coronary syndrome (NSTE-ACS) by the complete HEART score has not yet been assessed. We investigated whether pre-hospital risk stratification of patients with suspected NSTE-ACS using the HEART score is accurate in predicting major adverse cardiac events (MACE).

Methods:

This is a prospective observational study, including 700 patients with suspected NSTE-ACS. Risk stratification was performed by ambulance paramedics, using the HEART score; low risk was defined as HEART score ⩽ 3. Primary endpoint was occurrence of MACE within 45 days after inclusion. Secondary endpoint was myocardial infarction or death.

Results:

A total of 172 patients (24.6%) were stratified as low risk and 528 patients (75.4%) as intermediate to high risk. Mean age was 53.9 years in the low risk group and 66.7 years in the intermediate to high risk group ( p<0.001), 50% were male in the low risk group versus 60% in the intermediate to high risk group ( p=0.026). MACE occurred in five patients in the low risk group (2.9%) and in 111 (21.0%) patients at intermediate or high risk ( p<0.001). There were no deaths in the low risk group and the occurrence of acute myocardial infarction in this group was 1.2%. In the high risk group six patients died (1.1%) and 76 patients had myocardial infarction (14.4%).

Conclusions:

In suspected NSTE-ACS, pre-hospital risk stratification by ambulance paramedics, including troponin measurement, is accurate in differentiating between low and intermediate to high risk. Future studies should investigate whether transportation of low risk patients to a hospital can be avoided, and whether high risk patients benefit from immediate transfer to a hospital with early coronary angiography possibilities.

Value of Prehospital Troponin Assessment in Suspected Non-ST-Elevation Acute Coronary Syndrome

There is an increasing awareness that prehospital risk stratification in patients with suspected non-ST-elevation acute coronary syndrome (NSTE-ACS) is important. The HEART score accurately identifies patients at low risk and is nowadays fully assessable outside the hospital after the development of point-of-care (POC) troponin tests. However, the added value of the troponin component to the prehospital HEART score has not yet been assessed. This is a prospective cohort study including 700 patients with suspected NSTE-ACS in which prehospital risk stratification using the HEART score was performed by paramedics. Low risk was defined as HEAR or HEART score ≦3. Troponin was measured by a POC troponin T Test device (Roche Cobas h232). Troponin <40 ng/l scored 0 point, troponin ≥40 ng/l scored 2 points. Primary end point was major adverse cardiac events (MACE) within 45 days after inclusion. Mean HEAR score was 4.5 ± 1.6, mean HEART score was 4.7 ± 1.7. Using the HEAR score, a total of 183 patients (26%) were stratified as low risk, whereas using the HEART score, 172 patients (25%) were stratified as low risk (p = 0.001). In both low-risk groups, there were no deaths within 45 days. Using HEAR, MACE occurred in 13 patients (7%) in the low-risk group, whereas using HEART, MACE occurred in 5 patients in the low-risk group (3%, p <0.001). The use of HEART (Area under the curve 0.74) obtained a higher predictive value compared to HEAR (Area under the curve 0.65, p <0.001) for MACE. In conclusion, in patients with suspected NSTE-ACS, the prehospital troponin component of the HEART score has important added predictive value.

EurA1c: The European HbA1c Trial to Investigate the Performance of HbA1c Assays in 2166 Laboratories across 17 Countries and 24 Manufacturers by Use of the IFCC Model for Quality Targets

BACKGROUND

A major objective of the IFCC Committee on Education and Use of Biomarkers in Diabetes is to generate awareness and improvement of HbA1c assays through evaluation of the performance by countries and manufacturers.

METHODS

Fresh whole blood and lyophilized hemolysate specimens manufactured from the same pool were used by 17 external quality assessment organizers to evaluate analytical performance of 2166 laboratories. Results were evaluated per country, per manufacturer, and per manufacturer and country combined according to criteria of the IFCC model for quality targets.

RESULTS

At the country level with fresh whole blood specimens, 6 countries met the IFCC criterion, 2 did not, and 2 were borderline. With lyophilized hemolysates, 5 countries met the criterion, 2 did not, and 3 were borderline. At the manufacturer level using fresh whole blood specimens, 13 manufacturers met the criterion, 8 did not, and 3 were borderline. Using lyophilized hemolysates, 7 manufacturers met the criterion, 6 did not, and 3 were borderline. In both country and manufacturer groups, the major contribution to total error derived from between-laboratory variation. There were no substantial differences in performance between groups using fresh whole blood or lyophilized hemolysate samples.

CONCLUSIONS

The state of the art is that 1 of 20 laboratories does not meet the IFCC criterion, but there are substantial differences between country and between manufacturer groups. Efforts to further improve quality should focus on reducing between-laboratory variation. With some limitations, fresh whole blood and well-defined lyophilized specimens are suitable for purpose.

Technical and clinical validation of the Greiner FC-Mix glycaemia tube

BACKGROUND

Measurement of adequate glucose concentrations is complicated by in vitro breakdown of glucose due to glycolysis. Unlike the commonly used NaF-EDTA and NaF-oxalate phlebotomy tubes, citrated NaF-EDTA tubes are reported to directly and thereby completely inhibit glycolysis. Recently, Greiner introduced the Vacuette® FC-Mix NaF-EDTA-citrate tube, currently the only NaF-citrate tube without volume-disturbing liquid additions available on the European market. Here we present its potential as alternative for the laborious and therefore unfeasible conditions for glucose sampling as recommended by the World Health Organization (WHO).

METHODS

The FC-Mix tube was tested against the WHO recommended method of optimal laboratory conditions, both in healthy volunteers and pregnant woman undergoing oral glucose tolerance test (oGTT) for screening of gestational diabetes mellitus (GDM). Glucose concentrations were measured after different incubation times (0-48 h) and temperatures (room temperature, 37 °C), both in uncentrifuged whole blood and centrifuged material.

RESULTS

Deming regression analysis shows that glucose concentrations measured in the FC-Mix tube correlate to the WHO recommended method. Stability is maintained at room temperature for 48 h and at least 24 h at 37 °C. The use of the FC-Mix tube was also validated in screening for GDM and proved comparable to the WHO recommended method in diagnostic outcome.

CONCLUSIONS

The new Greiner FC-Mix tube combines the easy handling of a routine tube with dry additive with the ability to immediately inhibit glycolysis as in the WHO method for optimal pre-analytical and analytical conditions and performs equally to those conditions when screening for GDM.

Whole Blood Donation Affects the Interpretation of Hemoglobin A1c

Introduction

Several factors, including changed dynamics of erythrocyte formation and degradation, can influence the degree of hemoglobin A_1c (HbA_1c) formation thereby affecting its use in monitoring diabetes. This study determines the influence of whole blood donation on HbA_1c in both non-diabetic blood donors and blood donors with type 2 diabetes.

Methods

In this observational study, 23 non-diabetic blood donors and 21 blood donors with type 2 diabetes donated 475 mL whole blood and were followed prospectively for nine weeks. Each week blood samples were collected and analyzed for changes in HbA_1c using three secondary reference measurement procedures.

Results

Twelve non-diabetic blood donors (52.2%) and 10 (58.8%) blood donors with type 2 diabetes had a significant reduction in HbA_1c following blood donation (reduction >-4.28%, P < 0.05). All non-diabetic blood donors with a normal ferritin concentration predonation had a significant reduction in HbA_1c. In the non-diabetic group the maximum reduction was -11.9%, in the type 2 diabetes group -12.0%. When eligible to donate again, 52.2% of the non-diabetic blood donors and 41.2% of the blood donors with type 2 diabetes had HbA_1c concentrations significantly lower compared to their predonation concentration (reduction >-4.28%, P < 0.05).

Conclusion

Patients with type 2 diabetes contributing to whole blood donation programs can be at risk of falsely lowered HbA_1c. This could lead to a wrong interpretation of their glycemic control by their general practitioner or internist.

Fast assessment and management of chest pain patients without ST-elevation in the pre-hospital gateway (FamouS Triage): ruling out a myocardial infarction at home with the modified HEART score

BACKGROUND

The first study of the FamouS Triage project investigates the feasibility of ruling out a myocardial infarction in pre-hospital chest pain patients without electrocardiographic ST-segment elevation by using the modified HEART score at the patient's home, incorporating only a single highly sensitive troponin T measurement.

METHODS

A venous blood sample was drawn in the ambulance from 1127 consecutive chest pain patients for measurement of the pre-hospital highly sensitive troponin T levels, in order to establish a pre-hospital HEART score (i.e. the modified HEART score) and evaluate the possibility of triage at the patient's home. The primary endpoint was the occurrence of a major adverse cardiac event (MACE) i.e. acute myocardial infarction, percutaneous coronary intervention, coronary artery bypass grafting or death within 30 days after initial presentation.

RESULTS

Two hundred and six patients (18%) developed a MACE during 30 days of follow-up. Thirty-six per cent of the patients ( n=403) had a low modified HEART score (0-3 points) and none of them developed a MACE during follow-up. Forty-four per cent of the patients ( n=494) had an intermediate modified HEART score (4-6 points) and 18% of them developed a MACE. Twenty per cent of the patients ( n=230) had a high modified HEART score (7-10 points) of which 52% developed a MACE during follow-up.

CONCLUSION

It seems feasible to rule out a myocardial infarction at home in chest pain patients without ST-segment elevation by using the modified HEART score.

TRIAL ID

NTR4205. Dutch Trial Register [ http://www.trialregister.nl ]: trial number 4205.

Performance of the FreeStyle Libre Flash glucose monitoring system in patients with type 1 and 2 diabetes mellitus

OBJECTIVE

To evaluate the performance of the FreeStyle Libre Flash continuous glucose monitoring (FSL-CGM) system against established central laboratory methods.

RESEARCH DESIGN AND METHODS

20 subjects (8 type 1 diabetes mellitus, 12 type 2 diabetes mellitus) were analyzed. FSL-CGM sensor measurements (inserted in arm and abdomen) were compared with capillary blood glucose results analyzed with StatStrip as semigold standard. The glucose response after a standardized oral glucose load was measured by FSL-CGM and capillary samples analyzed by perchloric acid hexokinase (PCA-HK) method, StatStrip and FSL test strip (FSLC), and a commonly used CGM system (iPro2).

RESULTS

FSL-CGM arm sensor readings showed 85.5% of paired readings falling within Clarke Error Grid (ISO 15197:2013) zone A when compared with StatStrip. For FSL-CGM abdomen and FSLC, these percentages were 64% and 98%, respectively. The overall correlation of FSL-CGM in the arm and the StatStrip indicates a performance with lower results with the FSL-CGM in the arm than expected based on the StatStrip in the lower glucose ranges, and higher results than expected in the higher ranges. Following a standardized glucose load, a slower rise in glucose level was observed for FSL-CGM arm as compared with PCA-HK, StatStrip, FSLC, and iPro2 during the first 45-60 min after glucose load ingestion.

CONCLUSIONS

Certain matters need attention while using the FSL-CGM in daily life including the observed lower values in the lower ranges, and the underestimation of the effect of a meal on glucose response. These effects of such deviations can partly be overcome by optimizing the available user instructions.

TRIAL REGISTRATION NUMBER

TC5348; results.

The predictive value of cumulative lactate dehydrogenase release within the first 72 h of acute myocardial infarction in patients treated with primary angioplasty

Background: In patients with acute myocardial infarction, estimation of infarct size by cumulative lactate dehydrogenase release at 72 h (LDHQ72) is a simple and widely used method. Our objective was to study the value of estimating infarct size, by the cumulative release of LDH over 72, 60, 48 and 36 h in predicting left ventricular ejection fraction (LVef) and cardiac death at 1 year.

Methods: In the Zwolle Infarction Study infarct size estimated as LDHQ was calculated in 1224 patients treated with primary percutaneous coronary intervention for acute myocardial infarction between December 1993 and June 2001. Patients were categorized as having small (LDHQ72<800 U/L), medium (LDHQ72 800-2500 U/L) or large (LDHQ72>2500 U/L) myocardial infarction.

Results: LDHQ72 was closely correlated with LDHQ60, LDHQ48 and LDHQ36 ( r = 0.998, 0.993 and 0.987, respectively, P <0.0001). The relations between LDHQ infarct size classification and mean LVef (51% vs 45% vs 35%, P <0.001) or cardiac death at 1 year (0-0.3% vs 0.7-1% vs 6-8%) showed a similar pattern, irrespective of whether LDH was measured up to 36, 48, 60 or 72 h.

Conclusion: Infarct size classification based on LDHQ36 is an objective and widely available method for early risk stratification in patients treated with primary angioplasty for acute ST-segment elevation myocardial infarction.

Differences in interpretation of haemoglobin A1c values among diabetes care professionals

BACKGROUND

To assess the expected precision of HbA1c measurements and the magnitude of HbA1c changes eliciting the advice to change treatment among diabetes care professionals.

METHODS

A seven-item questionnaire was sent to participants through a website. The survey focused on physicians and nurses involved in diabetes care.

RESULTS

In total, 104 physicians, 177 diabetes specialist nurses, and 248 primary care nurses responded to the survey. A large number of the nurses (44%) and only a small number of the physicians (4%) were not aware of the inherent uncertainty of HbA1c results. Nurses considered adjusting therapy based on very small changes in HbA1c whereas physicians in general adhere to 0.5% (5.5 mmol÷mol) as a clinically meaningful cut-off point. After therapy adjustment, a very small (0.1%) or no increase in HbA1c was considered to be significant enough to conclude that glucose regulation has worsened by 49% of the nurses and only 13% of the physicians.

CONCLUSION

Significant differences exist in the interpretation of changes in HbA1c results between physicians and nurses. Nurses consider therapy changes based on very small changes in HbA1c, whereas physicians preferably agree to the clinically relevant change of 0.5% (5.5 mmol÷mol). Changing therapy based on relatively small changes in HbA1c might lead to undue adjustments in the treatment of patients with diabetes. There is a clear need for more training for all diabetes care professionals about both the clinical significance and accuracy of HbA1c measurements.

Fast assessment and management of chest pain without ST-elevation in the pre-hospital gateway: rationale and design

BACKGROUND

For chest pain patients without ST-segment elevation in the pre-hospital setting, current clinical guidelines merely offer in-hospital risk stratification and management, as opposed to chest pain patients with ST-segment elevation for whom there is a straightforward pre-hospital strategy for diagnosis, medication regimen and logistics. The FAMOUS TRIAGE study will assess the effects of introducing a pre-hospital triage system that reliably stratifies chest pain patients without ST-segment elevation into 1) patients at high risk for NSTEMI requiring a direct transfer to a PCI-hospital; 2) patients at intermediate risk for a major adverse cardiac event (MACE) who could be evaluated at the nearest non-PCI hospital; and 3) patients at low risk for MACE (benign non-cardiac chest pain) who could have further evaluation at home or in a primary care setting.

METHODS

The FAMOUS TRIAGE study will be performed in three phases. In the first phase an appropriate pre-hospital risk stratification tool will be designed for chest pain patients without ST-segment elevation by means of a retrospective and a prospective study. The second phase of the project represents the external validation of the risk stratification models, and in the third and final phase an optimal risk stratification tool will be implemented into clinical practice. Clinical and economical endpoints before and after implementation of the pre-hospital risk stratification tool will be compared to assess clinical benefit and cost-effectiveness.

CONCLUSION

The FAMOUS TRIAGE project is a triple phase study that aims to optimize the pre-hospital management of chest pain patients without ST-segment elevation by providing tools for pre-hospital identification of NSTEMI or exclusion of acute coronary syndrome at home.

TRIAL ID

NTR4205. Dutch Trial Register [http://www.trialregister.nl]: trial number 4205.

Three of 7 hemoglobin A1c point-of-care instruments do not meet generally accepted analytical performance criteria

BACKGROUND

In 2009, we investigated the conformance of 8 hemoglobin A(1c) (Hb A(1c)) point-of-care (POC) instruments. Since then, instruments have improved and new devices are available on the market. In this second study, we evaluated the performance of DCA Vantage, Afinion, InnovaStar, Quo-Lab, Quo-Test, Cobas B101, and B-analyst Hb A(1c) POC instruments.

METHODS

Clinical and Laboratory Standards Institute protocols EP-5 and EP-9 were applied to investigate imprecision, accuracy, and bias. We assessed bias using the mean of 3 certified secondary reference measurement procedures (SRMPs). Assay conformance with the National Glycohemoglobin Standardization Program (NGSP) certification criteria was also evaluated. Interference of common Hb variants was investigated for methods that could work with hemolysed material.

RESULTS

The total CVs for all instruments, except for the DCA Vantage at a high Hb A(1c) value, were ≤3.1% in SI units and ≤2.1% in Diabetes Control and Complications Trial (DCCT) units. Afinion, DCA Vantage, B-analyst, and Cobas B101 instruments passed the NGSP criteria with 2 different reagent lot numbers. Quo-Test, Quo-Lab, and InnovaStar instruments had a negative bias compared to the mean of the 3 SRMPs and failed NGSP criteria. Most of the common Hb variants did not interfere with the investigated instruments, except Hb AE for the Cobas B101.

CONCLUSIONS

Afinion, DCA Vantage, Cobas B101, and B-analyst instruments met the generally accepted performance criteria for Hb A(1c). Quo-Test, Quo-Lab, and InnovaStar met the criteria for precision but not for bias. Proficiency testing should be mandated for users of Hb A1c POC assays to ensure quality.

Haemoglobin A1c: Historical overview and current concepts

Since the discovery of the relation between increased concentrations of fast haemoglobin fractions in patients with diabetes mellitus compared to concentrations in subjects without diabetes mellitus by Samuel Rahbar and co-workers in 1969, glycated haemoglobin A1c (HbA1c) has become a "gold standard" for glucose management in patients with diabetes mellitus. Recently, HbA1c has been advocated as a diagnostic marker for diabetes mellitus, which further underlines the importance of HbA1c. There are currently more than 30 methods available on the market with an analytical performance ranging from poor to state of the art. This review describes the biochemistry of HbA1c and the concepts of analytical and biological variation with respect to the measurement of HbA1c. Subsequently, aspects regarding the discovery of HbA1c are described. In addition, an overview is given on the assays methods that are currently available for the measurement of HbA1c. Finally, recommendations for the minimally required analytical performance characteristics of the current HbA1c assays are presented.

Optimising drug prescribing and dispensing in subjects at risk for drug errors due to renal impairment: improving drug safety in primary healthcare by low eGFR alerts

OBJECTIVES

To assess the risk of medication errors in subjects with renal impairment (defined as an estimated glomerular filtration rate (eGFR) ≤40 ml/min/1.73 m(2)) and the effectiveness of automatic eGFR ≤40-alerts relayed to community pharmacists.

DESIGN

Clinical survey.

SETTING

The city of Zwolle, The Netherlands, in a primary care setting including 22 community pharmacists and 65 general practitioners.

PARTICIPANTS

All adults who underwent ambulatory creatine measurements which triggered an eGFR ≤40-alert.

PRIMARY AND SECONDARY OUTCOME MEASURES

The total number of ambulatory subjects with an eGFR ≤40-alert during the study period of 1 year and the number of medication errors related to renal impairment. The type and number of proposed drug adjustments recommended by the community pharmacist and acceptance rate by the prescribing physicians. Classification of all medication errors on their potential to cause an adverse drug event (ADE) and the actual occurrence of ADEs (limited to those identified through hospital record reviews) 1 year after the introduction of the alerts.

RESULTS

Creatine measurements were performed in 25 929 adults. An eGFR ≤40-alert was indicated for 5.3% (n=1369). This group had a median (IQR) age of 78 (69, 84) years, and in 73% polypharmacy (≥5 drugs) was present. In 15% (n=211) of these subjects, a medication error was detected. The proportion of errors increased with age. Pharmacists recommended 342 medication adjustments, mainly concerning diuretics (22%) and antibiotics (21%). The physicians' acceptance rate was 66%. Of all the medication errors, 88% were regarded as potential ADEs, with most classified as significant or serious. At follow-up, the ADE risk (n=40) appeared highest when the proposed medication adjustments were not implemented (38% vs 6%).

CONCLUSIONS

The introduction of automatic eGFR-alerts identified a considerable number of subjects who are at risk for ADEs due to renal impairment in an ambulatory setting. The nationwide implementation of this simple protocol could identify many potential ADEs, thereby substantially reducing iatrogenic complications in subjects with impaired renal function.

Prognostic value of admission glycosylated hemoglobin and glucose in nondiabetic patients with ST-segment-elevation myocardial infarction treated with percutaneous coronary intervention

BACKGROUND

In nondiabetic patients with ST-segment-elevation myocardial infarction, acute hyperglycemia is associated with adverse outcome. Whether this association is due merely to hyperglycemia as an acute stress response or whether longer-term glycometabolic derangements are also involved is uncertain. It was our aim to determine the association between both acute and chronic hyperglycemia (hemoglobin A(₁c) [HbA(₁c)]) and outcome in nondiabetic patients with ST-segment-elevation myocardial infarction.

METHODS AND RESULTS

This observational study included consecutive patients (n=4176) without known diabetes mellitus admitted with ST-segment-elevation myocardial infarction. All patients were treated with primary percutaneous intervention. Both glucose and HbA(1c) were measured on admission. Main outcome measure was total long-term mortality; secondary outcome measures were 1-year mortality and enzymatic infarct size. One-year mortality was 4.7%, and mortality after total follow-up (3.3 ± 1.5 years) was 10%. Both elevated HbA(1c) levels (P<0.001) and elevated admission glucose (P<0.001) were associated with 1-year and long-term mortality. After exclusion of early mortality (within 30 days), HbA(₁c) remained associated with long-term mortality (P<0.001), whereas glucose lost significance (P=0.09). Elevated glucose, but not elevated HbA(₁c), was associated with larger infarct size. After multivariate analysis, HbA(₁c) (hazard ratio, 1.2 per interquartile range; P<0.01), but not glucose, was independently associated with long-term mortality.

CONCLUSIONS

In nondiabetic patients with ST-segment-elevation myocardial infarction, both elevated admission glucose and HbA(₁c) levels were associated with adverse outcome. Both of these parameters reflect different patient populations, and their association with outcome is probably due to different mechanisms. Measurement of both parameters enables identification of these high-risk groups for aggressive secondary risk prevention.

One in five laboratories using various hemoglobin A1c methods do not meet the criteria for optimal diabetes care management

BACKGROUND

We assessed the reference change value (RCV) of currently available hemoglobin A(1c) (HbA(1c)) laboratory assays, which is defined as the critical difference between two consecutive HbA(1c) measurements representing a significant change in health status.

METHODS

We examined the individual laboratory coefficients of variation (CVs) in the Dutch/Belgian quality scheme based on 24 lyophilized samples and calculated the RCV per laboratory (n = 220) and per assay method. In addition, two pooled whole blood samples were sent to the participating laboratories. The individual laboratory results were compared to the assigned value ± an allowable total error (TE(a)) of 6%.

RESULTS

At HbA(1c) values of 41.0 mmol/mol (5.9%-Diabetes Control and Complications Trial [DCCT]) and 61.8 mmol/mol (7.8%-DCCT), 99% and 98%, respectively, of the laboratories reported a value within a TE(a) limit of 6%. The analytical CV of the HbA(1c) method used in 78% of the laboratories is <2.4%. The mean RCV at an HbA(1c) value of 53 mmol/mol (7.0%-DCCT) for methods of Bio-Rad is 5.9 mmol/mol (0.59%-DCCT); for Arkray/Menarini, 4.3 mmol/mol (0.43%-DCCT); for Roche, 6.5 mmol/mol (0.65%-DCCT); for Tosoh, 3.3 mmol/mol (0.33%-DCCT); and for other methods, 6.3 mmol/mol (0.63%-DCCT).

CONCLUSIONS

The analytical performance of the majority of laboratory HbA(1c) methods is within the clinical requirements. However, based on the calculated RCV, 21.8% of the laboratories using different HbA(1c) methods are not able to distinguish an HbA(1c) result of 59 mmol/mol (7.5%-DCCT) from a previous HbA(1c) result of 53 mmol/mol (7.0%-DCCT). It can be presumed that differences in HbA(1c) results of 5 mmol/mol (0.5%-DCCT) do influence treatment decisions.

Self-monitoring of blood glucose: the use of the first or the second drop of blood

OBJECTIVE

There is no general agreement regarding the use of the first or second drop of blood for glucose monitoring. This study investigated whether capillary glucose concentrations, as measured in the first and second drops of blood, differed ≥ 10% compared with a control glucose concentration in different situations.

RESEARCH DESIGN AND METHODS

Capillary glucose concentrations were measured in two consecutive drops of blood in the following circumstances in 123 patients with diabetes: without washing hands, after exposing the hands to fruit, after washing the fruit-exposed hands, and during application of different amounts of external pressure around the finger. The results were compared with control measurements.

RESULTS

Not washing hands led to a difference in glucose concentration of ≥ 10% in the first and in the second drops of blood in 11% and 4% of the participants, respectively. In fruit-exposed fingers, these differences were found in 88% and 11% of the participants, respectively. Different external pressures led to ≥ 10% differences in glucose concentrations in 5-13% of the participants.

CONCLUSIONS

We recommend washing the hands with soap and water, drying them, and using the first drop of blood for self-monitoring of blood glucose. If washing hands is not possible, and they are not visibly soiled or exposed to a sugar-containing product, it is acceptable to use the second drop of blood after wiping away the first drop. External pressure may lead to unreliable readings.

SKML-Quality Mark for point-of-care test (POCT) glucose meters and glucose meters for home-use

BACKGROUND

Point-of-care glucose meters are used increasingly in semi- and non-professional context. The quality of glucose measurements depends on the quality of the equipment, the quality of use, and the pre-analytical conditions. In this article, a External Quality Assessment Scheme (SKML)-Quality Mark for point-of-care test (POCT) and self-test glucose meters is proposed, assessing analytical quality and technical quality. The analytical requirements are based on the biological variation concept, and a system to assess meters for the SKML-Quality Mark is described. Using the proposed system as an example, 14 meters were tested.

METHODS

The analytical quality of the POCT and self-test equipment was assessed for plasma calibrated glucose values by comparison with a trueness verified method traceable to the IFCC reference method in an accredited clinical laboratory. The concept is based on the biological variation system. The SKML-Quality Mark comprises the following criteria for blood glucose equipment: 1) Fulfilment of compliance with ISO 15197 and/or TNO guideline criterion; 2) Fulfilment of the total allowable error (TAE) criterion; 3) Fulfilment of the total allowable linearity bias criterion; 4) Fulfilment of the total allowable interfering substances bias criterion; and 5) Fulfilment of the haematocrit criterion.

RESULTS

The proposed SKML-Quality Mark system was tested on 14 commercial home-use meters. The TAE criterion is violated by two meters. The main reason for the violation is bias. For the majority of meters, the Passing and Bablok regression confidence interval does not include the intercept of 0.0 and slope of 1.0. In addition, Syx indicates dispersion around the line or non-linearity. The bias and total error at three different concentrations were investigated as part of the quality mark, resulting in disapproval of the Dicomed Sensocard Plus meter. The bias was significant for the Wellion Linus. With respect to interfering substances, bias of the same magnitude and sign as the bias without additive was seen for all meters for acetaminophen, indicating no additional interference. For ascorbic acid, an additional bias was seen for several meters. However, significant bias was demonstrated for the Sensocard Plus and Glucocard X-meter.

CONCLUSIONS

The biological variation concept offers a scientific basis for assessment of acceptable deviation. The concept is extended in the SKML-Quality Mark correcting for the limited number of measurements that can be performed while assessing home-use or POCT meters. The results show that three out of 14 meters fail the proposed quality mark.

Self-monitoring of blood glucose in tablet-treated type 2 diabetic patients (ZODIAC)

BACKGROUND

Whether self-monitoring of blood glucose (SMBG) improves glycaemic control in patients with type 2 diabetes mellitus (T2DM) not using insulin is questionable. Our aim was to investigate the effects of SMBG in patients with T2DM who were in persistent moderate glycaemic control whilst not using insulin.

METHODS

Patients were eligible when between 18 and 70 years of age, with an HbA1c between 7 and 8.5%, using one or two oral blood glucose lowering agents. Forty-one of the anticipated 52 patients were randomly assigned to receive either SMBG added to usual care, or to continue with usual care for one year. A fasting glucose value and three postprandial glucose values were measured twice weekly (including a Saturday or a Sunday). The primary efficacy parameter was HbA1c. Furthermore, health-related quality of life and treatment satisfaction were assessed using the Short-form 36 Health Survey Questionnaire (SF-36), the Type 2 Diabetes Symptom Checklist (DSC-r), the Diabetes Treatment Satisfaction Questionnaire (DTSQ) and the WHO -Wellbeing Index (WHO-5).

RESULTS

Change in HbA1c between groups was -0.05% (95% CI: -0.51, 0.41; p=0.507). Also, there were no significant changes between groups on the DTSQ , DSC type 2, WHO-5 or SF -36, except for the SF -36 dimension 'health change' which was lower in the SBMG group (mean difference: -12 (95% CI: -20.9, -3.1).

CONCLUSION

On top of the absence of a clinical benefit, tablet-treated T2DM patients experienced some worsening of their health perception. We therefore argue that the use of SMBG in this patient group is questionable, and its unlimited use and promotion should be reconsidered.

A double-blind, randomized, placebo-controlled clinical trial on benfotiamine treatment in patients with diabetic nephropathy

OBJECTIVE

To investigate the effect of benfotiamine on urinary albumin excretion (UAE) and the tubular damage marker kidney injury molecule-1 (KIM-1) in patients with type 2 diabetes and nephropathy.

RESEARCH DESIGN AND METHODS

Patients with type 2 diabetes and UAE equivalent to 15-300 mg/24 h, despite ACE inhibitors (ACE-Is) or angiotensin receptor blockers (ARBs), were randomly assigned to 12 weeks of benfotiamine (900 mg/day) (n = 39) or placebo (n = 43).

RESULTS

Compared with placebo, benfotiamine treatment resulted in significant improvement of thiamine status (P < 0.001). Benfotiamine treatment did not significantly decrease 24-h UAE or 24-h KIM-1 excretion.

CONCLUSIONS

In patients with type 2 diabetes and nephropathy, high-dose benfotiamine treatment for 12 weeks in addition to ACE-Is or ARBs did not reduce UAE or KIM-1 excretion, despite improvement of thiamine status.

Glucose and Glycated Haemoglobin Point-of-care Testing and Early Diagnosis of Diabetes and Pre-diabetes

The number of individuals with impaired glucose metabolism (‘pre-diabetes’) and type 2 diabetes is reaching epidemic proportions. This increase is associated with higher cardiovascular morbidity and mortality. Early screening for diabetes and pre-diabetes (i.e. elevated glucose and/or glycated haemoglobin [HbA1c]) may aid in the reduction of diabetes-related complications. Point-of-care testing, defined as testing at or near the site of the patient, is able to bring diagnostic tests and its associated therapeutic actions immediately to the patient and may aid in the detection of diabetes and the reduction of complications. However, the majority of available point-of-care testing devices for glucose and HbA1cdo not meet generally accepted analytical performance criteria and may underestimate the true risk of diabetes. Until these analytical performance issues have been addressed properly, caution should be exercised in the use of point-of-care testing of glucose and HbA1c in the diagnosis of and screening for pre-diabetes and diabetes.

Six of eight hemoglobin A1c point-of-care instruments do not meet the general accepted analytical performance criteria

BACKGROUND

Hemoglobin A(1c) (Hb A(1c)) point-of-care (POC) instruments are widely used to provide rapid-turnaround results in diabetic care centers. We investigated the conformance of various Hb A(1c) POC instruments (In2it from Bio-Rad, DCA Vantage from Siemens, Afinion and Nycocard from Axis-Shield, Clover from Infopia, InnovaStar from DiaSys, A1CNow from Bayer, and Quo-Test from Quotient Diagnostics) with generally accepted performance criteria for Hb A(1c).

METHODS

The CLSI protocols EP-10, EP-5, and EP-9 were applied to investigate imprecision, accuracy, and bias. We assessed bias using 3 certified secondary reference measurement procedures and the mean of the 3 reference methods. Assay conformance with the National Glycohemoglobin Standardization Program (NGSP) certification criteria, as calculated from analyses with 2 different reagent lot numbers for each Hb A(1c) method, was also evaluated.

RESULTS

Because of disappointing EP-10 results, 2 of the 8 manufacturers decided not to continue the evaluation. The total CVs from EP-5 evaluations for the different instruments with a low and high Hb A(1c) value were: In2it 4.9% and 3.3%, DCA Vantage 1.8% and 3.7%, Clover 4.0% and 3.5%, InnovaStar 3.2% and 3.9%, Nycocard 4.8% and 5.2%, and Afinion 2.4% and 1.8%. Only the Afinion and the DCA Vantage passed the NGSP criteria with 2 different reagent lot numbers.

CONCLUSIONS

Only the Afinion and the DCA Vantage met the acceptance criteria of having a total CV <3% in the clinically relevant range. The EP-9 results and the calculations of the NGSP certification showed significant differences in analytical performance between different reagent lot numbers for all Hb A(1c) POC instruments.

Hemoglobin A1c point-of-care assays; a new world with a lot of consequences!

BACKGROUND

Point-of-care instruments for the measurement of hemoglobin A1c (HbA1c) may improve the glycemic control of people with diabetes by providing a rapid result if the performance of the instruments used is acceptable. A 0.5% HbA1c difference between successive results is considered a clinically relevant change. With this in mind, the In2it from Bio-Rad and the DCA Vantage from Siemens were evaluated according to Clinical and Laboratory Standards Institute (CLSI) protocols.

METHODS

The CLSI protocols EP-5 and EP-9 were applied to investigate precision, accuracy, and bias. The bias was compared with three certified secondary reference measurement procedures. Differences between capillary and venous blood were investigated by an end-user group consisting of nurse practitioners at a diabetes care center.

RESULTS

At HbA1c levels of 5.1 and 11.2%, total coefficients of variation (CV) for the In2it were 4.9 and 3.3%, respectively, and for the DCA Vantage were 1.7 to 1.8% and 3.7 to 5.5% depending on the lot number of the cartridges. Method comparisons showed significant lot number-dependent results for the In2it and the DCA Vantage compared with the three reference methods. No overall difference was observed between capillary and venous blood for both methods.

CONCLUSION

Performance results of the In2it and the DCA Vantage showed variable and lot number-dependent results. To maintain the interlaboratory CV of 5% for HbA1c, the Clinical Laboratory Improvement Amendments rules for waived point-of-care instruments should be revised. An obligation for participating in external quality schemes and taking adequate action should be considered for POC instruments that perform poorly.

Hemoglobin A1c determination in the A1C-Derived Average Glucose (ADAG) study

BACKGROUND

The A1C-Derived Average Glucose (ADAG) study was commenced to gain a better understanding of the relationship between HbA1c and average blood glucose and to investigate if HbA1c could be expressed in the same units as day-to-day glucose monitoring. Owing to the impact of the outcome of this study it was very important to determine HbA1c values with a minimum of uncertainty and as close as possible to the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) primary reference method, which is the only valid anchor of HbA1c standardization.

METHODS

Approximately 2300 samples were analyzed with four IFCC secondary reference methods. Additional off-line calibration with IFCC secondary reference material with assigned IFCC values was performed to improve the uncertainty in the HbA1c value determination.

RESULTS

Additional off-line calibration improved the 95% confidence interval between the four different HbA1c methods at HbA1c of 6.00% from +/-0.28% (5.72%-6.28%) to +/-0.20% (5.80%-6.20%) and at HbA(1c) of 9.00% from +/-0.43% (8.57%-9.43%) to +/-0.24% (8.76%-9.24%).

CONCLUSIONS

The HbA1c results used in the ADAG study were determined with the lowest uncertainty technically feasible by using four certified IFCC secondary reference methods and additional off-line calibration with IFCC secondary reference material.

Iron-induced platelet aggregation measurement: a novel method to measure platelet function in stenting for ST segment elevation myocardial infarction

BACKGROUND

Iron and (stainless) steel are potent platelet aggregation activators, and may be involved in stent thrombosis, a serious complication after intracoronary stenting. Current platelet function tests are suboptimal, because of inappropriate agonists and/or lack of reproducibility. We tested the feasibility and reproducibility of a novel platelet function test using stainless steel as an agonist and compared it with other platelet function tests.

MATERIALS AND METHODS

In 111 patients with acute ST segment elevation myocardial infarction (STEMI), duplo measurements of iron (Fe)-induced platelet aggregation (FIPA) were performed after clopidogrel, acetylsalicylic acid and/or tirofiban treatment. Within 1 h, citrated blood samples drawn from the femoral sheath before primary percutaneous coronary intervention were added to 100 mg of low carbon steel and after 5 s mixing with vortex, the samples were incubated for 15 min. The ratio between the non-aggregated platelets in the agonist sample and platelets in a reference sample was calculated as the platelet aggregation inhibition.

RESULTS

FIPA measurement was highly reproducible (correlation coefficient (R)=0.942, P<0.001 between duplo samples). FIPA correlated well with adenosine diphosphate-induced platelet aggregation (R=0.83, P<0.001) but weakly with platelet function analyser-100 bleeding time (R=0.56, P<0.001). FIPA could be measured in patients in which platelet aggregation could not be measured by platelet function analyser-100 or after adenosine diphosphate.

CONCLUSION

This study showed good reproducibility of a novel platelet function test using stainless steel as an agonist and showed correlation with validated platelet function tests. We found that the novel platelet function test is a suitable test for measurement of platelet aggregation inhibition in patients undergoing stenting for STEMI, even when they are taking multiple antiplatelet regimens.

Pre- and postoperative accuracy and safety of a real-time continuous glucose monitoring system in cardiac surgical patients: a randomized pilot study

BACKGROUND

Our objective was to evaluate the accuracy and safety of a real-time (RT) continuous glucose monitoring system (CGMS) in patients before and after cardiothoracic surgery and to investigate whether activation of the alarm function of the RT-CGMS had an effect on glucose control.

METHODS

Patients scheduled for elective cardiothoracic procedures, without a history of insulin-requiring diabetes, were perioperatively monitored with RT-CGMS for 72 h and were randomized into two groups: with or without the alarm function (set at 4 and 10 mmol/L) of the device activated. Sensor values were compared with capillary, arterial, and venous blood glucose values. Percentages of time spent in various glucose ranges were compared between groups.

RESULTS

There were no adverse effects of the RT-CGMS. Of the 1,001 sensor value comparisons with capillary or arterial measurements, 96.6% fell within Clarke Error Grid zones A and B, with relative absolute differences ranging from 15% (preoperative period) to 12% (intensive care unit period) to 14% (postoperative period on the ward). Seventeen (7.9%) arterial and 16 (2.0%) capillary comparisons fell within zone D or E. Whether or not the alarm function, as used in this pilot study, was activated did not affect time spent in different glucose ranges.

CONCLUSIONS

Although the RT-CGMS is safe and accurate according to accepted standards, there are still small aberrations, which in our opinion preclude unlimited use in its present form in a clinical setting. The effect of the alarm function at different glucose levels remains to be investigated.