Evaluation of the Glucometer Elite XL device for screening for neonatal hypoglycaemia

Continuous glucose monitoring in neonates: a review

Continuous glucose monitoring (CGM) is well established in the management of diabetes mellitus, but its role in neonatal glycaemic control is less clear. CGM has provided important insights about neonatal glucose metabolism, and there is increasing interest in its clinical use, particularly in preterm neonates and in those in whom glucose control is difficult. Neonatal glucose instability, including hypoglycaemia and hyperglycaemia, has been associated with poorer neurodevelopment, and CGM offers the possibility of adjusting treatment in real time to account for individual metabolic requirements while reducing the number of blood tests required, potentially improving long-term outcomes. However, current devices are optimised for use at relatively high glucose concentrations, and several technical issues need to be resolved before real-time CGM can be recommended for routine neonatal care. These include: 1) limited point accuracy, especially at low or rapidly changing glucose concentrations; 2) calibration methods that are designed for higher glucose concentrations of children and adults, and not for neonates; 3) sensor drift, which is under-recognised; and 4) the need for dynamic and integrated metrics that can be related to long-term neurodevelopmental outcomes. CGM remains an important tool for retrospective investigation of neonatal glycaemia and the effect of different treatments on glucose metabolism. However, at present CGM should be limited to research studies, and should only be introduced into routine clinical care once benefit is demonstrated in randomised trials.

The accuracy of a glucose-oxidase-based point-of-care glucometer in premature infants

OBJECTIVE

The purpose of this study was to evaluate the accuracy of a novel commercial glucose-oxidase (GO)-based glucometer in measuring glucose concentrations in arterial blood samples collected from premature infants.

PATIENTS AND METHODS

A commercial glucometer, which is a plasma separation GO-based glucometer, was employed to compare the accuracy of the commercial blood glucometer with that of a standard glucose analyser for monitoring blood glucose levels in premature infants. Arterial blood samples were collected and analysed, including samples adjusted for specific glucose (3.6 mmol/L, 8.3 mmol/L and 16.7 mmol/L) and PaO2 levels (range, 40-400 mm Hg).

RESULTS

In total, 159 samples were collected. Bland-Altman analysis showed good correlation between the commercial glucometer and standard glucose analyser. Error-grid analysis revealed that all of the results were within zone A (ie, the clinically accurate estimate zone). The biases between the two systems were low at different PaO2 levels and haematocrits. Finally, the influence of different PaO2 levels was within acceptable ranges.

CONCLUSIONS

The GO-based glucometer evaluated in this study provides accurate results even when measured at high PaO2 and different haematocrits and is suitable for measuring arterial glucose levels in premature infants.

Hypoglycemia in critically ill children

BACKGROUND

The practice of glycemic control with intravenous insulin in critically ill patients has brought clinical focus on understanding the effects of hypoglycemia, especially in children. Very little is published on the impact of hypoglycemia in this population. We aimed to review the existing literature on hypoglycemia in critically ill neonates and children.

METHODS

We performed a systematic review of the literature up to August 2011 using PubMed, Ovid MEDLINE and ISI Web of Science using the search terms "hypoglycemia or hypoglyc*" and "critical care or intensive care or critical illness". Articles were limited to "all child (0-18 years old)" and "English".

RESULTS

A total of 513 articles were identified and 132 were included for review. Hypoglycemia is a significant concern among pediatric and neonatal intensivists. Its definition is complicated by the use of a biochemical measure (i.e., blood glucose) for a pathophysiologic problem (i.e., neuroglycopenia). Based on associated outcomes, we suggest defining hypoglycemia as <40-45 mg/dl in neonates and <60-65 mg/dl in children. Below the suggested threshold values, hypoglycemia is associated with worse neurological outcomes, increased intensive care unit stay, and increased mortality. Disruptions in carbohydrate metabolism increase the risk of hypoglycemia incritically ill children. Prevention of hypoglycemia, especially in the setting of intravenous insulin use, will be best accomplished by the combination of accurate measuring techniques, frequent or continuous glucose monitoring, and computerized insulin titration protocols.

CONCLUSION

Studies on hypoglycemia in critically ill children have focused on spontaneous hypoglycemia. With the current practice of maintaining blood glucose within a narrow range with intravenous insulin, the risk factors and outcomes associated with insulin-induced hypoglycemia should be rigorously studied to prevent hypoglycemia and potentially improve outcomes of critically ill children.

Clinical performance of the new glucometer in the nursery and neonatal intensive care unit

BACKGROUND

  Performance of point-of-care (POC) glucometers in newborns have been unsatisfactory in low glucose concentration range and the effects of different hematocrit levels on glucose measurements have also demonstrated in currently used POC glucometers.

METHODS

  The aim of this study was to evaluate the performance of the new glucometer (Nova-Statstrip(®) ; Nova Biomedical, Waltham, MA, USA) compared to the reference method. Venous blood specimens of neonates were collected and tested by the two glucometers. Standard reference was performed using the hexokinase method within 10 min of blood collection. Hematocrit and total serum bilirubin measurements were performed simultaneously.

RESULTS

  One hundred and fifty-one blood specimens were collected and measured by the reference method with plasma glucose concentrations ranging from 12 to 371 mg/dL. Twenty-one specimens had plasma glucose concentrations <45 mg/dL. At plasma glucose concentrations less than 75 mg/dL, the Statstrip(®) achieved 93% in the tests for discrepancy < 15 mg/dL. At a glucose concentration more than 75 mg/dL, 97% of the Statstrip(®) readings were within 20% of the reference values. The mean difference (±2SD) of the Statstrip(®) was 2.8 (-14.1, 19.7) mg/dL. At a hypoglycemic level (<45 mg/dL), it showed a sensitivity of 95.2%. No significant interference of hematocrit or total serum bilirubin was found on the mean bias of the Statstrip(®) .

CONCLUSION

  The new glucometer (Nova-Statstrip(®) ) could be used for point-of-care blood glucose measurement in neonates as it showed a narrow margin of error and had no hematocrit or bilirubin interference.

Evaluation of different POCT devices for glucose measurement in a clinical neonatal setting

Hypoglycaemia is a major cause of neonatal morbidity and may induce long-term developmental sequelae. Clinical signs of hypoglycaemia in neonatal infants are unspecific or even absent, and therefore, precise and accurate methods for the assessment of glycaemia are needed. Glycaemia measurement in newborns has some particularities like a very low limit of normal glucose concentration compared to adults and a large range of normal haematocrit values. Many bedside point-of-care testing (POCT) systems are available, but literature about their accuracy in newborn infants is scarce and not very convincing. In this retrospective study, we identified over a 1-year study period 1,324 paired glycaemia results, one obtained at bedside with one of three different POCT systems (Elite™ XL, Ascensia™ Contour™ and ABL 735) and the other in the central laboratory of the hospital with the hexokinase reference method. All three POCT systems tended to overestimate glycaemia values, and none of them fulfilled the ISO 15197 accuracy criteria. The Elite XL appeared to be more appropriate than Contour to detect hypoglycaemia, however with a low specificity. Contour additionally showed an important inaccuracy with increasing haematocrit. The bench analyzer ABL 735 was the most accurate of the three tested POCT systems. Both of the tested handheld glucometers have important drawbacks in their use as screening tools for hypoglycaemia in newborn infants. ABL 735 could be a valuable alternative, but the blood volume needed is more than 15 times higher than for handheld glucometers. Before daily use in the newborn population, careful clinical evaluation of each new POCT system for glucose measurement is of utmost importance.

Quality of glucose measurement with blood glucose meters at the point-of-care: relevance of interfering factors

AIM

A good understanding of the relevance of interfering factors having an impact on blood glucose (BG) measurement is needed to obtain the required quality. This depends on the application in which meters designed for self-monitoring of BG (SMBG) are used.

METHODS

By means of a literature search all publications (from January 1, 1980 to August 10, 2009) were identified that report about the influence of potentially interfering substances/factors on the measurement quality of BG meters.

RESULTS

Certain substances (e.g., maltose) can have a profound and misleading impact on the BG measurement result when the enzymatic reaction embedded on the given test strips cross-reacts. Also, a number of other drugs (e.g., acetaminophen) and factors (like temperature and altitude) affect the reliability of BG measurement massively. However, the susceptibility of the BG meter (depending on the enzyme technology of the test strips) differs significantly.

CONCLUSIONS

In daily practice the factors that have a relevant impact on the reliability of BG measurements with modern BG meters are rarely met. Clearly this also depends on the intended use (SMBG in patient hands vs. point-of-care testing in hospitals). To avoid misleading measurement results requires adequate training of all people involved.

Measurement of glucose levels in the newborn

Accurate measurement of blood glucose levels in the newborn is important as hypoglycaemia and hyperglycaemia are common treatable conditions and there is evidence linking both with detrimental clinical outcomes. Point of care (POC) glucose testing provides rapid results with small sample volumes and therefore clinical care can be modified quickly if needed. However the common thresholds for the diagnosis of hypoglycaemia in the newborn (blood glucose <2.0 mmol/l or <2.6 mmol/l) and hyperglycaemia (blood glucose >10 mmol/l) are at the limits of accuracy for many POC glucose analysers. Therefore although useful for screening, such devices cannot be relied upon for accurate diagnosis of hypoglycaemia. Stand alone local laboratory devices or glucose biosensors incorporated into blood gas analysers help to balance the benefits of POC testing with the accuracy of laboratory analyses. However these clinical methods all rely on intermittent blood sampling and there may be many hours between measurements, when both hypoglycaemia and hyperglycaemia may be undetected clinically. Less invasive and continuous methods of glucose monitoring are under development. Continuous glucose monitoring provides detailed information regarding glucose levels and has led to improvements in the care of patients with diabetes mellitus. These devices also have the potential to help provide improved glucose monitoring and management in the high risk neonate.

Assessing the Quality of Glucose Monitor Studies: A Critical Evaluation of Published Reports

Background: In recent years, a large number of studies have been published on the performance of glucose monitors. The quality of these reports is not known.

Methods: We searched the PubMed database for performance evaluations of handheld glucose monitors published from August 2002 to November 2006. Relevant articles were compared to 20 recommendations from the Standards for Reporting Diagnostic Accuracy (STARD) and 18 recommendations from the Clinical and Laboratory Standards Institute (CLSI).

Results: A total of 52 reports met our inclusion criteria and were reviewed. None (0%) of the reports conformed to all 38 STARD and CLSI recommendations. The range of compliance to these recommendations varied widely (median 53%; range 21%–84%). Only 1 study of the 52 reported following a CLSI recommendation for checking reference test results. Fewer than half (42%) of the reports contained STARD-recommended statements regarding how and when comparative measurements were performed.

Conclusions: None of the glucose monitor reports from our review conformed to all STARD and CLSI recommendations. Our finding that the average rate of compliance to recommendations was low suggests that many of the researchers did not follow published recommendations for study design, methodology, and reporting and that study quality and conclusions may have been affected. Future studies evaluating the performance of glucose monitoring systems should be carefully designed and follow published recommendations for methodological and reporting quality.