Abstract
Blood glucose is vital for many physiological pathways and can be quantified by clinical chemistry analyzers and in-house point-of-care (POC) devices. Pre-analytical and analytical factors can influence blood glucose measurements. This project aimed to investigate pre-analytical factors on whole blood and plasma glucose measurements in loggerhead sea turtles (Caretta caretta) by evaluating the effects of storage (refrigeration) up to 48h after sampling and of packed cell volume (PCV) on whole blood glucose analysis by POC glucometer (time series n = 13); and by evaluating the effects of storage (room temperature and refrigeration) on plasma glucose concentrations using a dry slide chemistry analyzer (DCA) at various conditions: immediate processing and delayed plasma separation from erythrocytes at 24h and 48h (time series n = 14). The POC glucometer had overall strong agreement with the DCA (CCC = 0.76, r = 0.84, Cb = 0.90), but consistently overestimated glucose concentrations (mean difference: +0.4 mmol/L). The POC glucometer results decreased significantly over time, resulting in a substantial decline within the first 2h (0.41±0.47 mmol/L; 8±9%) that could potentially alter clinical decisions, thereby highlighting the need for immediate analysis using this method. The effects of PCV on glucose could not be assessed, as the statistical significance was associated with one outlier. Storage method significantly affected plasma glucose measurements using DCA, with room temperature samples resulting in rapid decreases of 3.57±0.89 mmol/L (77±9%) over the first 48h, while refrigerated samples provided consistent plasma glucose results over the same time period (decrease of 0.26±0.23 mmol/L; 6±5%). The results from this study provide new insights into optimal blood sample handling and processing for glucose analysis in sea turtles, show the suitability of the POC glucometer as a rapid diagnostic test, and confirm the reliability of plasma glucose measurements using refrigeration. These findings emphasize the need to consider pre-/analytical factors when interpreting blood glucose results from loggerhead sea turtles.
Highlights
The loggerhead sea turtle (Caretta caretta) is a worldwide distributed marine turtle species, currently classified as “vulnerable” by the International Union for Conservation of Nature, with an overall decreasing population trend [1]
EasyTouch1 glucose analysis showed a systematic positive bias in loggerhead sea turtles in this study, overestimating glucose measurements when compared to the dry slide chemistry analyzer (DCA)
The POC glucometer presented a systematic positive bias, overestimating glucose measurements when compared to the DCA
Summary
The loggerhead sea turtle (Caretta caretta) is a worldwide distributed marine turtle species, currently classified as “vulnerable” by the International Union for Conservation of Nature, with an overall decreasing population trend [1]. A large number of stranded loggerhead sea turtles are treated and monitored each year by rehabilitation facilities around the world [3]. Laboratory diagnostics, such as blood glucose measurements, are routinely used for diagnosis, prognosis, and patient monitoring. The monitoring of blood glucose concentrations in human and small animal medicine represents a cornerstone for critically-ill patient care, similar to its diagnostic utility in reptile medicine. Reptile blood glucose measurements generally vary between 1.4 and 8.3 mmol/L and tend to be lower than blood glucose concentrations of birds and mammals [7,8]
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