Best Practice Guideline articleMeasurement of glucose levels in the newborn
Introduction
The accurate measurement of blood glucose in the newborn is clinically important as hypoglycaemia and hyperglycaemia are not always associated with overt clinical signs [1], although both extremes have been associated with poor clinical outcomes [2], [3]. As interventions are available to maintain glucose levels within a ‘normal range’ it is important that glucose levels can be measured efficiently and accurately so that any necessary clinical interventions can be made. Accuracy of measurement is dependent on many factors related to the sample itself and device used for analyses. There is a wide range of devices and different methodologies available for measurement of glucose and it is important that devices are validated for use in the newborn before being used for clinical care. One of the particular difficulties in the newborn is that the blood glucose (BG) levels at the thresholds for changes in clinical management are at levels that are at the limits of the accuracy for many glucose analysers. New methods such as continuous subcutaneous glucose monitoring are increasingly being used to help improve glucose control in patients with diabetes mellitus and may in the future provide the opportunity to improve glucose management in the newborn.
Section snippets
Why measure glucose levels?
Hypoglycaemia can be detected after birth in a healthy population of term neonates, as part of physiological adaptation [4], and therefore routine testing of all babies is not indicated. The fasting newborn produces lactate and ketones which can be used as alternative fuels in the neonatal period having a glucose sparing effect. However infants who are unable to produce alternative fuels due to limited fat and glycogen reserves or impaired counter regulation are at risk from hypoglycaemia. In
How should glucose levels be measured?
Balancing efficiency and accuracy are the factors that influence decisions regarding the choice of method for measuring glucose levels. In infants requiring intensive care BG levels may change quickly and they therefore require frequent glucose measurements. Therefore minimal sample volumes must be used to avoid the need for frequent blood transfusions, and rapid results are required so that changes in clinical care can be made in a timely fashion. However this has to be balanced by the
Current clinical methods for measuring glucose levels
The first line in glucose measurement in most clinical settings is a point of care glucose meter. Point of care testing can provide rapid results (in as little as 3 s) using small sample volumes (as small as 0.3 μl). This is potentially helpful in providing efficient clinical care and has been shown to reduce the need for blood transfusions [17]. There have been dramatic developments in point of care devices for measurement of glucose over the last 40 years. The first dry reagent blood glucose
Continuous glucose monitoring
Current clinical methods for measuring glucose in the newborn rely on blood sampling to provide single one off measures. Developments in continuous subcutaneous glucose monitoring can now provide detailed information on glucose levels throughout the 24-hour period. Continuous glucose monitoring has demonstrated that glucose levels can fluctuate widely particularly in infants requiring intensive care and may result in undetected periods of both hypoglycaemia and hyperglycaemia [31] (Fig. 1).
Non invasive devices
Attempts have also been made to develop non invasive techniques to measure glucose levels to prevent the need for frequent blood sampling. Such methodologies include optical sensors or transdermal devices but attempts have generally been unsuccessful. Optical sensors measure the characteristics of reflected light that are changed as a result of an interaction with glucose. Spectrophotometry is based on specific absorption in different spectral ranges with glucose concentration derived
Summary
The ability to measure glucose levels in the newborn is a critical part of good clinical care. Glucose monitoring devices need to give accurate results particularly at levels that would affect clinical care. However devices also need to be practical to use and maintain by neonatal staff and cost efficient. There is a wide range of methodologies and devices available for measurement of glucose but it is important that devices are validated for use in the newborn before being used for clinical
Key guidelines
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Accurate measurement of glucose levels in the newborn at risk of hyperglycaemia or hypoglycaemia is important.
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Accuracy of any measurement is affected by both preanalytical and analytical errors.
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POC devices although useful for screening cannot be relied upon for the diagnosis of hypoglycaemia.
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Laboratory analyses although considered the gold standard will give inaccurately low levels if there is a delay in samples being analysed.
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Optimal glucose levels in the newborn are not known.
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Any new
Research directions
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What are optimal glucose levels for the newborn both term and preterm?
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What are the optimal interventions to achieve these targets?
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Validation of the use of continuous glucose monitoring as part of clinical care
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Development of improved methods for non invasive continuous glucose monitoring in the newborn
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