Abstract
BackgroundHypovitaminosis C and vitamin C deficiency are common in critically ill patients and associated with organ dysfunction. Low vitamin C status often goes unnoticed because determination is challenging. The static oxidation reduction potential (sORP) reflects the amount of oxidative stress in the blood and is a potential suitable surrogate marker for vitamin C. sORP can be measured rapidly using the RedoxSYS system, a point-of-care device. This study aims to validate a model that estimates plasma vitamin C concentration and to determine the diagnostic accuracy of sORP to discriminate between decreased and higher plasma vitamin C concentrations.MethodsPlasma vitamin C concentrations and sORP were measured in a mixed intensive care (IC) population. Our model estimating vitamin C from sORP was validated by assessing its accuracy in two datasets. Receiver operating characteristic (ROC) curves with areas under the curve (AUC) were constructed to show the diagnostic accuracy of sORP to identify and rule out hypovitaminosis C and vitamin C deficiency. Different cut-off values are provided.ResultsPlasma vitamin C concentration and sORP were measured in 117 samples in dataset 1 and 43 samples in dataset 2. Bias and precision (SD) were 1.3 ± 10.0 µmol/L and 3.9 ± 10.1 µmol/L in dataset 1 and 2, respectively. In patients with low plasma vitamin C concentrations, bias and precision were − 2.6 ± 5.1 µmol/L and − 1.1 ± 5.4 µmol in dataset 1 (n = 40) and 2 (n = 20), respectively. Optimal sORP cut-off values to differentiate hypovitaminosis C and vitamin C deficiency from higher plasma concentrations were found at 114.6 mV (AUC 0.91) and 124.7 mV (AUC 0.93), respectively.ConclusionsORP accurately estimates low plasma vitamin C concentrations and can be used to screen for hypovitaminosis C and vitamin C deficiency in critically ill patients. A validated model and multiple sORP cut-off values are presented for subgroup analysis in clinical trials or usage in clinical practice.
Highlights
Vitamin C plasma concentrations are often decreased in critically ill patients [1]
Plasma vitamin C concentration and static oxidation reduction potential (sORP) measurements In dataset 2, plasma vitamin C concentration was measured in 25 patients at day 1 and 21 patients at day 3. 3 out of 46 samples were excluded as their plasma vitamin C concentrations were > 150 μmol/L due to vitamin C therapy
Sequential Organ Failure Assessment (SOFA)-scores were calculated according to the NICE criteria [30] c Measured in patients d Measured in patients e Measured in 21 patients f Measured in 36 patients g Measured in 35 patients
Summary
Vitamin C plasma concentrations are often decreased in critically ill patients [1]. Low vitamin C status often goes unnoticed, because determination of the plasma vitamin C concentrations is challenging. A novel way to screen patients rapidly for low plasma vitamin C concentrations is relevant for both clinicians who consider vitamin C administration and researchers who want to perform a stratified trial analysis. A potential suitable marker for this purpose is the static oxidation reduction potential (sORP), which reflects the amount of oxidative stress in the blood. Hypovitaminosis C and vitamin C deficiency are common in critically ill patients and associated with organ dysfunction. The static oxidation reduction potential (sORP) reflects the amount of oxidative stress in the blood and is a potential suitable surrogate marker for vitamin C. This study aims to validate a model that estimates plasma vitamin C concentration and to determine the diagnostic accuracy of sORP to discrimi‐ nate between decreased and higher plasma vitamin C concentrations
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