Validated Protein Analysis Improves Caretta Caretta Health Assessments

Caretta caretta is the predominant sea turtle nesting along the coasts of the Mediterranean Sea. It is listed as a vulnerable species in the IUCN red list, because it is threatened by human activities. Protein electrophoresis is an important diagnostic tool in sea turtles rehabilitation, providing information on inflammatory, nutritional and epatic status. The aim of this study was to compare the electrophoretic profiles of protein fractions in paired serum and plasma samples from loggerhead sea turtles (Caretta caretta) admitted to the Centro di Referenza Nazionale sul Benessere, Monitoraggio e Diagnostica delle Malattie delle Tartarughe Marine (C.Re.Ta.M.) in Sicily. Biometric parameters were recorded for 40 individuals (n =17 juveniles and n = 23 subadults). Peripheral venous blood was collected from each turtle upon admission, before any treatment was administered, and paired serum and lithium-heparin plasma samples were analyzed in parallel. Normality of the paired differences between plasma and serum measurements was assessed for each protein fraction using the Shapiro-Wilk test. For the overall study population, the Wilcoxon signed-rank test was used because the paired differences did not meet the assumption of normality. In the age-stratified analyses, paired t-tests were applied when the paired differences were normally distributed, whereas the Wilcoxon signed-rank test was used when normality was not met. Agreement between serum and plasma measurements was further evaluated using Bland-Altman analysis. The bias was calculated as the mean difference between the two matrices, and the 95% limits of agreement (LoA) were calculated as the bias ± 1.96 SD. A P < 0.05 was considered statistically significant. In juveniles, a statistically significant difference was observed for β-globulin 2 (P = 0.0202), with higher concentrations in plasma than in serum. This finding may be related to differences in the contribution of fibrinogen to this electrophoretic fraction. Overall, serum and lithium-heparin plasma showed broadly comparable electrophoretic profiles in hospitalized Caretta caretta turtles under the conditions investigated. However, the observed differences and limits of agreement should be considered when interpreting individual protein fractions, and further studies are warranted before considering the two matrices fully interchangeable for diagnostic purposes.