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. 2022 May 5;17(5):1321–1325. doi: 10.1177/19322968221092763

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© 2022 Diabetes Technology Society

This article is distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 License (https://creativecommons.org/licenses/by-nc/4.0/) which permits non-commercial use, reproduction and distribution of the work without further permission provided the original work is attributed as specified on the SAGE and Open Access pages (https://us.sagepub.com/en-us/nam/open-access-at-sage).

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Figure 3. — Normalized glucose error over extreme variations in blood glucose concentrations, hematocrit, and sodium concentration in remaining blood samples from patients treated in different intensive care units in Frankfurt (N = 2843). Anonymized intensive care unit samples (leftover samples) without information on medication were obtained from a clinic in Frankfurt (surgery and neurological intensive care) and, if possible (if sufficient volume), divided into 2 aliquots. Each sample was measured natively after receipt (first aliquot). The second aliquot was glycolyzed overnight and then measured. Alternatively, this aliquot was spiked with glucose and measured. Directly after the respective measurement, plasma was obtained for the reference analysis. This procedure covered the medically relevant measurement range (50-400 mg/dL). The glucose reference concentrations were obtained by the plasma hexokinase method on a cobas^® lab analyzer (Roche Diagnostics GmbH). The hematocrit reference levels of the tested blood samples were obtained by the centrifuge tube method. The sodium reference concentrations were obtained by ion selective electrodes method on a cobas^® C analyzer (Roche Diagnostics GmbH). Individual deviations of system measurement results versus the glucose reference method taken for the same sample as tested with the system are shown. Test results below 75 mg/dL glucose are shown as absolute bias and test results above 75 mg/dL glucose are shown as a relative bias (the “Normalized Error”). The horizontal bands represent specification boundaries for the normalized glucose error: 95% of all samples must be within −12 and 12, and 98% within −15 and 15. The deviations were plotted 3 times versus different x-axes, representing the reference glucose concentration, the hematocrit level, and the sodium concentration of the tested blood samples (measured with established reference methods). Blue lines are the regression lines calculated for the bias values. All received samples were tested as received (native). A certain number of samples (in cases of a sufficient available volume) was also tested with the glycolyzed blood sample (to achieve low glucose concentrations) and after spiking with glucose (to achieve higher glucose concentrations).