Uncovering Rare Mutations: an Unforeseen Complication of Routine Genotyping of Apoe

tremely important to good patient care in the neonatal intensive care setting, and the laboratory is frequently challenged to provide a more rapid and sensitive means of determining blood glucose in the hypoglycemic infant (1 ). Recently, several point-of-care testing instruments have been developed that allow for on-site glucose testing at the low end of the dynamic range of glucose measurements (2 ). We recently evaluated the Precision-G System by MediSense, which can determine glucose on a 5-mL blood specimen in 20 s at the bedside with a dynamic range that extends to 1.11 mmol/L (20 mg/ dL). Seventy-four consecutive blood samples from the neonatal unit were collected by heelstick into lithium heparin capillary tubes, and glucose was determined simultaneously on an Ortho Clinical Diagnostics Vitros 950 analyzer and the Precision-G System. The neonatal population we studied demonstrated the usual range of normal to high hematocrit values as well as increased bilirubin, providing assurance that these variables did not influence the results. Comparative results between these two methods are shown in Fig. 1. Regression analysis of the glucose values obtained with the Precision-G and the Vitros 950 (Fig. 1) revealed a correlation coefficient of 0.993 (Syux 5 0.43 mmol/L), an intercept 5 20.053 (6 0.002) mmol/L, and a slope of 0.946 (6 0.051). Although the number of samples in the true hypoglycemic range was rather limited, the results from 14 subjects with glucose results below 2.22 mmol/L (40 mg/ dL) fell on the regression line. Overall, there was a slight negative systematic difference observed with the Precision-G results that averaged 0.31 mmol/L; differences in the analytical methods and the use of whole blood vs plasma sample most likely account for this difference. This slight difference, however, should have little influence on the neonatologist’s clinical decision regarding the detection of hypoglycemia. Between-run imprecision (CV) with the Precision-G using Abbott MediSense control material at 1.11 mmol/L (20 mg/dL) was 8% (n 5 15). It is our impression from these results that the Precision-G System can be used effectively to determine low blood glucose concentrations in a neonatal unit.