[Erroneous diagnosis 'neonatal hypoglycemia' due to incorrect preservation of blood samples]

The high frequency of neonatal hypoglycaemia found in the St. Catherine's Hospital, Eindhoven [corrected], (8.2% of all newborn infants had values of 1.8 mmol/l glucose or less) promoted us to test the effects of the different conditions of blood preservation before measuring in a consecutive series of 18 newborn infants at risk for hypoglycaemia. When blood was preserved in microtest tubes coated with sodium fluoride (NaF) and measured after 1 hour at room temperature, the glucose level decreased by 7 to 36%. Storage on melting ice for one hour prevented this decline completely. In our hospital sodium fluoride coated microtest tubes are used. They were found to contain various concentrations of NaF, ranging from 0.85 to 2.65 mg/ml. In a 2nd experiment with cord blood from 8 patients, we proved that a concentration of 16 mg/ml sodium fluoride was necessary to inhibit glycolysis and to prevent a fall of plasma glucose. The rapid determination of blood glucose values, i.e. within 10 minutes after the blood sample is taken, decreased, as expected, the frequency of hypoglycaemia in the newborn at risk.