J. Perinat. Med. 2015; 43(3): 373–375
Letter to the Editor Abdul Qader Tahir Ismail*, Oluwarotimi Bello and Vikki Fradd
Glucose measurements and gold standards DOI 10.1515/jpm-2014-0214 Received June 25, 2014. Accepted September 15, 2014. Previously published online October 8, 2014.
Dear Sir, The debate for a definition of neonatal hypoglycemia has been ongoing since the 1980s. In many units, an operational threshold of 2.6 mmol/L is used – a value of blood glucose above which it is sufficient without requiring presence of alternate fuel sources (e.g., ketone bodies) [4]. But even this varies for neonates at increased risk of hyperinsulinemia, with decreased bodily reserves, or who are symptomatic. Symptoms are stereotypical and include poor feeding, floppiness, apneic episodes, altered level of consciousness, and seizures; and while the evidence is poor that asymptomatic hypoglycemia leads to any longterm neurodevelopmental effects [1, 2, 5, 16], it is more substantial if symptomatic, including learning disabilities, cerebral palsy, and seizure disorders [2, 8, 12]. The fear of potential neurological damage and its long-term effects drive our conservative approach. Simultaneously, the debate is ongoing regarding adequate testing methods. Although bedside devices have an advantage due to their practicality, they are generally considered inappropriate for use in neonates due to limitations on their accuracy at low glucose concentrations [2, 6], and in the presence of common metabolic disturbances (e.g., metabolic acidosis, raised PaO2, hyperbilirubinemia, and high and low hematocrit [6, 7, 13–15]). Despite their recognized shortfalls, they are in widespread use in neonatal units, including our own at Birmingham Heartlands Hospital, and they are often used with the proviso that hypoglycemic values require verification. In our unit, we use a laboratory-processed result in this situation, but as it may take some time to obtain this, we necessarily base clinical decisions upon the bedside test, which may result in inappropriate action or inaction. *Corresponding author: Abdul Qader Tahir Ismail, Heartlands Hospital, Birmingham, UK, E-mail: [email protected] Oluwarotimi Bello and Vikki Fradd: Heartlands Hospital, Birmingham, UK
This is further confounded with issues surrounding the reliability of this gold standard. Fluoride oxalate sample tubes inhibit enolase in the glycolytic pathway but not for the first 30–90 min at room temperature. During this time, glycolysis continues, so potentially creating a discrepancy between true and laboratory glucose results depending on laboratory transit time [3, 9]. Our local guidelines state that a laboratory glucose should be obtained with one bedside result
Letter to the Editor Abdul Qader Tahir Ismail*, Oluwarotimi Bello and Vikki Fradd
Glucose measurements and gold standards DOI 10.1515/jpm-2014-0214 Received June 25, 2014. Accepted September 15, 2014. Previously published online October 8, 2014.
Dear Sir, The debate for a definition of neonatal hypoglycemia has been ongoing since the 1980s. In many units, an operational threshold of 2.6 mmol/L is used – a value of blood glucose above which it is sufficient without requiring presence of alternate fuel sources (e.g., ketone bodies) [4]. But even this varies for neonates at increased risk of hyperinsulinemia, with decreased bodily reserves, or who are symptomatic. Symptoms are stereotypical and include poor feeding, floppiness, apneic episodes, altered level of consciousness, and seizures; and while the evidence is poor that asymptomatic hypoglycemia leads to any longterm neurodevelopmental effects [1, 2, 5, 16], it is more substantial if symptomatic, including learning disabilities, cerebral palsy, and seizure disorders [2, 8, 12]. The fear of potential neurological damage and its long-term effects drive our conservative approach. Simultaneously, the debate is ongoing regarding adequate testing methods. Although bedside devices have an advantage due to their practicality, they are generally considered inappropriate for use in neonates due to limitations on their accuracy at low glucose concentrations [2, 6], and in the presence of common metabolic disturbances (e.g., metabolic acidosis, raised PaO2, hyperbilirubinemia, and high and low hematocrit [6, 7, 13–15]). Despite their recognized shortfalls, they are in widespread use in neonatal units, including our own at Birmingham Heartlands Hospital, and they are often used with the proviso that hypoglycemic values require verification. In our unit, we use a laboratory-processed result in this situation, but as it may take some time to obtain this, we necessarily base clinical decisions upon the bedside test, which may result in inappropriate action or inaction. *Corresponding author: Abdul Qader Tahir Ismail, Heartlands Hospital, Birmingham, UK, E-mail: [email protected] Oluwarotimi Bello and Vikki Fradd: Heartlands Hospital, Birmingham, UK
This is further confounded with issues surrounding the reliability of this gold standard. Fluoride oxalate sample tubes inhibit enolase in the glycolytic pathway but not for the first 30–90 min at room temperature. During this time, glycolysis continues, so potentially creating a discrepancy between true and laboratory glucose results depending on laboratory transit time [3, 9]. Our local guidelines state that a laboratory glucose should be obtained with one bedside result
