Analytical validation of a portable human Accu-Chek glucometer in honeybee hemolymph

Glucose and trehalose are the main energy sources used by honeybees (Apis mellifera) for daily activities. However, there is no validated point-of-care method to reliably measure both sugars. We performed an analytical validation of a portable human glucometer (Accu-Chek; Roche) for glucose measurement in honeybee hemolymph compared to a reference method (GluCH, UniCel DxC 600; Beckman Coulter). We used 30 pooled hemolymph samples collected from the antennae of anesthetized honeybees and diluted 1:4 in 0.9% saline. We evaluated dilution linearity, spike recovery, and inter- and intra-assay imprecision. Glucose concentration was measured over time (2 h, 4 h, 8 h, 12 h, 1 d, 2 d, 3 d, 7 d, 21 d, 28 d) at various storage temperature (25°C, 4°C, -20°C, -80°C). The trehalose concentration was measured indirectly by trehalase hydrolyzation. Glucose concentrations measured by both instruments had a strong correlation (0.985, p < 0.0001) and a bias of -7.33 mmol/L (±1.96SD: 13.70 to -28.36), with linear agreement at <20 mmol/L (physiologic value: 100 mmol/L). The accuracy of the glucometer decreased at >20 mmol/L. Recovery of 115-130% of diluted spikes indicated good specificity. Inter- and intra-assay imprecision were 2.50% and 2.21%, respectively. Glucose concentrations fluctuated in stored samples dependent on time and temperature; however, glucose concentrations were constant with storage at -80°C for ≥28 d. The Accu-Chek glucometer is an adequate instrument to measure honeybee glucose concentration in hemolymph diluted with 0.9% NaCl, with good accuracy and precision at <20 mmol/L. Hemolymph storage at -80°C is suitable for long-term conservation of glucose.

Smartphone-Based Electrochemical Systems for Glucose Monitoring in Biofluids: A Review

As a vital biomarker, glucose plays an important role in multiple physiological and pathological processes. Thus, glucose detection has become an important direction in the electrochemical analysis field. In order to realize more convenient, real-time, comfortable and accurate monitoring, smartphone-based portable, wearable and implantable electrochemical glucose monitoring is progressing rapidly. In this review, we firstly introduce technologies integrated in smartphones and the advantages of these technologies in electrochemical glucose detection. Subsequently, this overview illustrates the advances of smartphone-based portable, wearable and implantable electrochemical glucose monitoring systems in diverse biofluids over the last ten years (2012-2022). Specifically, some interesting and innovative technologies are highlighted. In the last section, after discussing the challenges in this field, we offer some future directions, such as application of advanced nanomaterials, novel power sources, simultaneous detection of multiple markers and a closed-loop system.

Skin Patchable Sensor Surveillance for Continuous Glucose Monitoring

Diabetes mellitus is a physiological and metabolic disorder affecting millions of people worldwide, associated with global morbidity, mortality, and financial expenses. Long-term complications can be avoided by frequent, continuous self-monitoring of blood glucose. Therefore, this review summarizes the current state-of-art glycemic control regimes involving measurement approaches and basic concepts. Following an introduction to the significance of continuous glucose sensing, we have tracked the evolution of glucose monitoring devices from minimally invasive to non-invasive methods to present an overview of the spectrum of continuous glucose monitoring (CGM) technologies. The conveniences, accuracy, and cost-effectiveness of the real-time CGM systems (rt-CGMs) are the factors considered for discussion. Transdermal biosensing and drug delivery routes have recently emerged as an innovative approach to substitute hypodermal needles. This work reviews skin-patchable glucose monitoring sensors for the first time, providing specifics of all the major findings in the past 6 years. Skin patch sensors and their progressive form, i.e., microneedle (MN) array sensory and delivery systems, are elaborated, covering self-powered, enzymatic, and non-enzymatic devices. The critical aspects reviewed are material design and assembly techniques focusing on flexibility, sensitivity, selectivity, biocompatibility, and user-end comfort. The review highlights the advantages of patchable MNs' multi-sensor technology designed to maintain precise blood glucose levels and administer diabetes drugs or insulin through a "sense and act" feedback loop. Subsequently, the limitations and potential challenges encountered from the MN array as rt-CGMs are listed. Furthermore, the current statuses of working prototype glucose-responsive "closed-loop" insulin delivery systems are discussed. Finally, the expected future developments and outlooks in clinical applications are discussed.

Hybrid Technologies Combining Solid-State Sensors and Paper/Fabric Fluidics for Wearable Analytical Devices

The development of diagnostic tools for measuring a wide spectrum of target analytes, from biomarkers to other biochemical parameters in biological fluids, has experienced a significant growth in the last decades, with a good number of such tools entering the market. Recently, a clear focus has been put on miniaturized wearable devices, which offer powerful capabilities for real-time and continuous analysis of biofluids, mainly sweat, and can be used in athletics, consumer wellness, military, and healthcare applications. Sweat is an attractive biofluid in which different biomarkers could be noninvasively measured to provide rapid information about the physical state of an individual. Wearable devices reported so far often provide discrete (single) measurements of the target analytes, most of them in the form of a yes/no qualitative response. However, quantitative biomarker analysis over certain periods of time is highly demanded for many applications such as the practice of sports or the precise control of the patient status in hospital settings. For this, a feasible combination of fluidic elements and sensor architectures has been sought. In this regard, this paper shows a concise overview of analytical tools based on the use of capillary-driven fluidics taking place on paper or fabric devices integrated with solid-state sensors fabricated by thick film technologies. The main advantages and limitations of the current technologies are pointed out together with the progress towards the development of functional devices. Those approaches reported in the last decade are examined in detail.

Opportunistic screening of cardiovascular disease risk factors in community pharmacies in Nigeria: a cross-sectional study

Background Early identification and treatment of cardiovascular disease (CVD) risk factors through screening are crucial in the primary prevention of CVD and reduction in healthcare-related costs. Use of Non-Physician Healthcare-workers including Community Pharmacists has been advocated as an effective and cost-efficient model of healthcare delivery. In Nigeria the use of community pharmacists for mass screening of CVD risk factors has not been explored. Objective We sought to investigate the possibility of mass CVD risk factor screening in community pharmacies by pharmacists. Setting Lagos, Nigeria. Methods Between October and December 2018 eight hundred and eighty-nine apparently healthy participants were screened for obesity, hypertension, diabetes and hypercholesterolaemia in ten community pharmacies. Diabetes and hypercholesterolaemia were screened for using point-of-care testing modalities. A structured questionnaire was used to obtain the socio-demographic data of the participants. Main outcome measures Prevalence of overweight/obesity, hypertension, diabetes, hypercholesterolaemia, smoking and alcohol intake. Results Mean age of the subjects was 56.8 ± 21.1 years. Majority (57.4%) were females. Prevalence of smoking and alcohol intake were 4.3% and 26.7% respectively. 59.7% and 71.5% of males and females were either overweight (BMI ≥ 25 kg/m²) or obese (BMI ≥ 30 kg/m²) respectively. Prevalence of hypertension was 28.2% in all subjects, 30.9% in males and 26.3% in females, p < 0.001. Using BP > 130/80 mmHg prevalence of hypertension was 55.1%. Diabetes was detected in 3% of the subjects while 45.3% had hypercholesterolaemia. In total, 64.1% of the subjects were diagnosed with CVD risk factors for the first time. Conclusion Opportunistic screening for CVD risk factors is possible in community pharmacies and has the ability to detect previously undiagnosed risk factors. This community pharmacy based model could serve as a cost-effective approach to primary prevention of CVD.

Comparison of glucose concentrations in serum, plasma, and blood measured by a point-of-care glucometer with serum glucose concentration measured by an automated biochemical analyzer for canine and feline blood samples

OBJECTIVE

To determine the correlation between glucose concentrations in serum, plasma, and blood measured by a point-of-care glucometer (POCG) and serum glucose concentration measured by an automated biochemical analyzer (ABA; gold standard).

SAMPLE

152 canine and 111 feline blood samples.

PROCEDURES

For each sample, the glucose concentration in serum, plasma, and blood was measured by a POCG and compared with the ABA-measured glucose concentration by means of the Lin concordance correlation coefficient. Results were summarized by species for all samples and subsets of samples with hyperglycemia (ABA-measured glucose concentration > 112 mg/dL for dogs and > 168 mg/dL for cats) and pronounced hyperglycemia (ABA-measured glucose concentration > 250 mg/dL for both species). The effect of PCV on correlations between POCG and ABA measurements was also assessed.

RESULTS

Hyperglycemia and pronounced hyperglycemia were identified in 69 and 36 canine samples and 44 and 29 feline samples, respectively. The POCG-measured glucose concentrations in serum, plasma, and blood were strongly and positively correlated with the gold standard concentration. The PCV was positively associated with the correlation between the POCG-measured blood glucose concentration and the gold standard concentration but was not associated with the correlations between the POCG-measured glucose concentrations in serum and plasma and the gold standard concentration.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that POCG-measured glucose concentrations in serum, plasma, and blood were strongly correlated with the ABA-measured serum glucose concentration, even in hyperglycemic samples. Given the time and labor required to harvest serum or plasma from blood samples, we concluded that blood was the preferred sample type for use with this POCG.

Highly specific and rapid glycan based amperometric detection of influenza viruses

Rapid and precise detection of influenza viruses in a point of care setting is critical for applying appropriate countermeasures. Current methods such as nucleic acid or antibody based techniques are expensive or suffer from low sensitivity, respectively. We have developed an assay that uses glucose test strips and a handheld potentiostat to detect the influenza virus with high specificity. Influenza surface glycoprotein neuraminidase (NA), but not bacterial NA, cleaved galactose bearing substrates, 4,7di-OMe N-acetylneuraminic acid attached to the 3 or 6 position of galactose, to release galactose. In contrast, viral and bacterial NA cleaved the natural substrate, N-acetylneuraminic acid attached to the 3 or 6 position of galactose. The released galactose was detected amperometrically using a handheld potentiostat and dehydrogenase bearing glucose test strips. The specificity for influenza was confirmed using influenza strains and different respiratory pathogens that include Streptococcus pneumoniae and Haemophilus influenzae; bacteria do not cleave these molecules. The assay was also used to detect co-infections caused by influenza and bacterial NA. Viral drug susceptibility and testing with human clinical samples was successful in 15 minutes, indicating that this assay could be used to rapidly detect influenza viruses at primary care or resource poor settings using ubiquitous glucose meters.

A community pharmacy-based cardiovascular risk screening service implemented in Iran

BACKGROUND

Cardiovascular disease is a major health concern around the world.

OBJECTIVE

To assess the outcomes and feasibility of a pharmacy-based cardiovascular screening in an urban referral community pharmacy in Iran.

METHODS

A cross sectional study was conducted in a referral community pharmacy. Subjects aged between 30-75 years without previous diagnose of cardiovascular disease or diabetes were screened. Measurement of all major cardiovascular risk factors, exercise habits, medical conditions, medications, and family history were investigated. Framingham risk score was calculated and high risk individuals were given a clinical summary sheet signed by a clinical pharmacist and were encouraged to follow up with their physician. Subjects were contacted one month after the recruitment period and their adherence to the follow up recommendation was recorded.

RESULTS

Data from 287 participants were analyzed and 146 were referred due to at least one abnormal laboratory test. The results showed 26 patients with cardiovascular disease risk greater than 20%, 32 high systolic blood pressure, 22 high diastolic blood pressures, 50 high total cholesterol levels, 108 low HDL-C levels, and 22 abnormal blood glucose levels. Approximately half of the individuals who received a follow up recommendation had made an appointment with their physician. Overall, 15.9% of the individuals received medications and 15.9% received appropriate advice for risk factor modification. Moreover, 7.5% were under evaluation by a physician.

CONCLUSION

A screening program in a community pharmacy has the potential to identify patients with elevated cardiovascular risk factor. A plan for increased patient adherence to follow up recommendations is required.

The association of hyperglycaemia with prevalent tuberculosis: a population-based cross-sectional study

BACKGROUND

Systematic reviews suggest that the incidence of diagnosed tuberculosis is two- to- three times higher in those with diabetes mellitus than in those without. Few studies have previously reported the association between diabetes or hyperglycaemia and the prevalence of active tuberculosis and none in a population-based study with microbiologically-defined tuberculosis. Most have instead concentrated on cases of diagnosed tuberculosis that present to health facilities. We had the opportunity to measure glycaemia alongside prevalent tuberculosis. A focus on prevalent tuberculosis enables estimation of the contribution of hyperglycaemia to the population prevalence of tuberculosis.

METHODS

A population-based cross-sectional study was conducted among adults in 24 communities from Zambia and the Western Cape (WC) province of South Africa. Prevalent tuberculosis was defined by the presence of a respiratory sample that was culture positive for M. tuberculosis. Glycaemia was measured by random blood glucose (RBG) concentration. Association with prevalent tuberculosis was explored across the whole spectrum of glycaemia.

RESULTS

Among 27,800 Zambian and 11,367 Western Cape participants, 4,431 (15.9%) and 1,835 (16.1%) respectively had a RBG concentration ≥7.0 mmol/L, and 405 (1.5%) and 322 (2.8%) respectively had a RBG concentration ≥11.1 mmol/L. In Zambia, the prevalence of tuberculosis was 0 · 5% (142/27,395) among individuals with RBG concentration <11.1 mmol/L and also ≥11.1 mmol/L (2/405); corresponding figures for WC were 2 · 5% (272/11,045) and 4 · 0% (13/322). There was evidence for a positive linear association between hyperglycaemia and pulmonary prevalent tuberculosis. Taking a RBG cut-off 11.1 mmol/L, a combined analysis of data from Zambian and WC communities found evidence of association between hyperglycaemia and TB (adjusted odds ratio = 2 · 15, 95% CI [1 · 17-3 · 94]). The population attributable fraction of prevalent tuberculosis to hyperglycaemia for Zambia and WC combined was 0.99% (95% CI 0 · 12%-1.85%) for hyperglycaemia with a RBG cut-off of 11.1 mmol/L.

CONCLUSIONS

This study demonstrates an association between hyperglycaemia and prevalent tuberculosis in a large population-based survey in Zambia and Western Cape. However, assuming causation, this association contributes little to the prevalence of TB in these populations.

Falsely Elevated Glucose Concentrations in Peritoneal Dialysis Patients Using Icodextrin

BACKGROUND

Peritoneal dialysis (PD) is used as an alternative to hemodialysis in end-stage renal disease (ESRD). Icodextrin has been used as a hyperosmotic agent in PD. The aim of the study was to assess two different point-of-care testing (POCT) glucose strips, affected and not affected by icodextrin, with serum glucose concentrations of the patients using and not using icodextrin.

METHODS

Fifty-two chronic ambulatory peritoneal dialysis (CAPD) patients using icodextrin (Extraneal®) and 20 CAPD patients using another hyperosmotic fluid (Dianeal®) were included in the study. Duplicate capillary and serum glucose concentrations were measured with two different POCT glucose strips and central laboratory hexokinase method. Assay principles of glucose strips were based on glucose dehydrogenase-pyrroloquinoline quinone (GDH-PQQ) and a mutant variant of GDH (Mut Q-GDH). The results of both strips were compared with those of hexokinase method.

RESULTS

Regression equations between POCT and hexokinase methods in icodextrin group were y = 2.55x + 1.12 mmol/l and y = 1.057x + 0.16 mmol/l for the GDH-PQQ and Mut Q-GDH methods, respectively. The mean difference between the results of hexokinase and those of GDH-PQQ and Mut Q-GDH in icodextrin group was 3.41 ± 1.56 and 0.72 ± 0.64 mmol/l, respectively. However, the mean differences were found much lower in the control group; 0.64 mmol/l for GDH-PQQ and 0.52 mmol/l for Mut Q-GDH.

CONCLUSION

Compared to GDH-PQQ, glucose strips of Mut Q-GDH correlated better with hexokinase method in PD patients using icodextrin.

Comparative performance assessment of point-of-care testing devices for measuring glucose and ketones at the patient bedside

Point-of-care (POC) testing devices for monitoring glucose and ketones can play a key role in the management of dysglycemia in hospitalized diabetes patients. The accuracy of glucose devices can be influenced by biochemical changes that commonly occur in critically ill hospital patients and by the medication prescribed. Little is known about the influence of these factors on ketone POC measurements. The aim of this study was to assess the analytical performance of POC hospital whole-blood glucose and ketone meters and the extent of glucose interference factors on the design and accuracy of ketone results. StatStrip glucose/ketone, Optium FreeStyle glucose/ketone, and Accu-Chek Performa glucose were also assessed and results compared to a central laboratory reference method. The analytical evaluation was performed according to Clinical and Laboratory Standards Institute (CLSI) protocols for precision, linearity, method comparison, and interference. The interferences assessed included acetoacetate, acetaminophen, ascorbic acid, galactose, maltose, uric acid, and sodium. The accuracies of both Optium ketone and glucose measurements were significantly influenced by varying levels of hematocrit and ascorbic acid. StatStrip ketone and glucose measurements were unaffected by the interferences tested with exception of ascorbic acid, which reduced the higher level ketone value. The accuracy of Accu-Chek glucose measurements was affected by hematocrit, by ascorbic acid, and significantly by galactose. The method correlation assessment indicated differences between the meters in compliance to ISO 15197 and CLSI 12-A3 performance criteria. Combined POC glucose/ketone methods are now available. The use of these devices in a hospital setting requires careful consideration with regard to the selection of instruments not sensitive to hematocrit variation and presence of interfering substances.

Glucose meters - fit for clinical purpose

Glucose meters have improved considerably since they were first introduced in 1960, but many questions are being asked about their accuracy and reliability in certain clinical situations. These questions have arisen because of the widespread use of these meters into clinical areas they have not been designed for such as critical care. The lack of understanding by some health professionals on factors that affect glucose results, such as sample type, glucose test strip methodologic limitations, calibration to recognized reference methods, and interferences, leads to misleading results that may affect patient care. Much debate continues on the quality specifications for glucose meters. Because there is an extensive use of these meters in different clinical scenarios, the setting of quality specifications will remain a challenge for regulatory and professional organizations. In this article, we have attempted to collect and provide relevant information addressing the limitations above. Pivotal to obtaining the best quality of results is education, particularly for diabetic patients monitoring their glucose. The International Federation of Clinical Chemistry and Laboratory Medicine through its Point-of-Care Testing Task Force and its Working Group on Glucose Point-of-Care Testing is actively working toward improving the quality of glucose results by improving education and working with the industry to improve strip performance and work toward the better standardization of strips.

Defining the relationship between average glucose and HbA1c in patients with type 2 diabetes and chronic kidney disease

AIMS

To examine the relationship between average glucose (AG) and HbA1c in patients with and without chronic kidney disease (CKD) and type 2 diabetes.

MATERIALS AND METHODS

43 patients with diabetes and CKD (stages 3-5) with stable glycaemic control, and glucose-lowering and erythropoiesis stimulating agent (ESA) doses, were prospectively studied for 3 months and compared to 104 age-matched controls with diabetes, without CKD from the ADAG study. Over 3 months, AG was calculated from 7 to 8 point self-monitored blood glucose measurements (SMBG) and from continuous glucose monitoring (CGMS), and mean HbA1c was calculated from 4 measurements. AG and HbA1c relationships were determined using multivariable linear regression analyses.

RESULTS

The CKD and non-CKD groups were well matched for age and gender. Mean AG tended to be higher (p=0.08) but HbA1c levels were similar (p=0.68) in the CKD compared with non-CKD groups. A linear relationship between AG and HbA1c was observed irrespective of the presence and stage of CKD. The relationship was weaker in patients with stage 4-5 CKD (non-CKD R2=0.75, stage 3 CKD R2=0.79 and stage 4-5 CKD R2=0.34, all p<0.01). The inclusion of ESA use in the model rendered the effect of CKD stage insignificant (R2=0.67, p<0.01).

CONCLUSIONS

In patients with type 2 diabetes and CKD there is a linear relationship between HbA1c and AG that is attenuated by ESA use, suggesting that ESA results in a systematic underestimation of AG derived from HbA1c.

Evaluation of portable blood glucose meters for measurement of blood glucose concentration in ferrets (Mustela putorius furo)

OBJECTIVE

To evaluate agreement of 3 models of portable blood glucose meters (PBGMs; 2 designed for use with human samples and 1 designed for veterinary use) with a laboratory analyzer for measurement of blood glucose concentrations in ferrets (Mustela putorius furo).

DESIGN

Evaluation study.

ANIMALS

52 ferrets.

PROCEDURES

Samples were analyzed with 4 PBGMs (whole blood) and a laboratory analyzer (plasma). Two PBGMs of the model designed for veterinary use were tested; each was set to a code corresponding to canine or feline sample analysis throughout the study. Agreement and bias between measurements obtained with the PBGMs and the laboratory analyzer were assessed with Bland-Altman plots. Linear regression analysis was performed to evaluate associations with venipuncture site by comparison of central (jugular) and peripheral (lateral saphenous or cephalic) venous blood samples.

RESULTS

Plasma glucose concentrations measured with the laboratory analyzer ranged from 41 to 160 mg/dL. Results from the PBGM for veterinary use coded to test a canine blood sample had the greatest agreement with the laboratory analyzer (mean bias, 1.9 mg/dL); all other PBGMs significantly underestimated blood glucose concentrations. A PBGM designed for use with human samples had the least agreement with the laboratory analyzer (mean bias, -34.0 mg/dL). Blood glucose concentration was not significantly different between central and peripheral venous blood samples for any analyzer used.

CONCLUSIONS AND CLINICAL RELEVANCE

Significant underestimation of blood glucose concentrations as detected for 3 of the 4 PBGMs used in the study could have a substantial impact on clinical decision making. Verification of blood glucose concentrations in ferrets with a laboratory analyzer is highly recommended.

Assessing the quality of publications evaluating the accuracy of blood glucose monitoring systems

Many studies determine the performance of blood glucose monitoring (BG) systems. Correct evaluation is, however, complex, and apparent contradiction of results creates confusion. This study aimed to provide an overview of frequently made errors and to develop easy-to-use checklists to verify the quality of such studies. Building on the work from Mahoney and Ellison and subsequent re-evaluation, study designs of accuracy studies were assessed, and best practice and internationally accepted norms were determined. Key issues were collated, and two simplified checklists were developed: one for the assessment of analytical accuracy studies and a second for guidance with studies assessing the influence of interferences. The checklists have been used in a feasibility study with 20 representative studies selected from a literature search between 2007 and 2012. This check revealed that limitations in the designs and methods of studies assessing the performance of BG systems are common. The use of the accuracy checklist with the 20 representative studies showed that only 20% were in agreement with most of the issues deemed important and that 40% showed clear nonconcordance with ISO 15197. The use of the interference checklist showed that only 50% of the publications were in good agreement with the quality checks. In agreement with previous studies, which concluded many evaluations are performed poorly and present questionable conclusions, the use of these checklists demonstrated that few publications adhered to international guidelines and recommendations. Taking this into consideration, it becomes obvious that the publications must be examined in more detail to establish their quality and the validity of conclusions drawn.

Evaluation of the relationship between capillary and venous plasma glucose concentrations obtained by the HemoCue Glucose 201+ system during an oral glucose tolerance test

In 55 women with previous gestational diabetes mellitus, simultaneous capillary and venous plasma glucose concentrations were measured at 0, 30 and 120 min during a 75 g oral glucose tolerance test (OGTT). The aims of the study were to examine the relationship between capillary and venous glucose measurements, and to establish equations for the conversion of capillary and venous glucose concentrations using the HemoCue Glucose 201+ system. Additionally, the correlation between the capillary and venous glucose concentrations with the diagnostic cut-off limits proposed by the World Health Organization (WHO) in 1999 was evaluated. Capillary glucose concentrations were consistently higher than venous glucose concentrations at all time points of the OGTT (p < 0.001), and the correlations between the measurements were statistically highly significant (p < 0.001). The differences between the samples were greatest in the non-fasting state as revealed by the 95% prediction intervals (mmol/L) in Bland-Altman plots; ± 0.54 at 0 min, ± 2.01 at 30 min, and ± 1.35 at 120 min. Equivalence values for capillary plasma glucose concentrations derived from this study tended to be higher than those proposed by the WHO as diagnostic cut-off limits. Stratifying subjects by glucose tolerance status according to the WHO criteria revealed disagreements related to glucose values close to the diagnostic cut-off points. The study findings highlight the uncertainty associated with derived equivalence values. However, capillary plasma glucose measurements could be suitable for diagnostic purposes in epidemiological studies and when translating results on a group basis.

Correction of an unexpected increasing trend in glucose measurements during 7 years recruitment to a cohort study

OBJECTIVES

To study an unexpected, significant increase in glucose measurements during 7 year recruitment to a cohort study.

DESIGN AND METHODS

Measurements of quality control solutions and blood glucose in pregnant women were done by Accu-Chek Sensor glucometer. Time-trends were analysed by regression models and control charts.

RESULTS

Cohort measurements were de-trended by weighted linear regressions based on independent control values.

CONCLUSIONS

Biologically implausible trends in data can be corrected by using independent control values.