Determination of a plasma retinol reference interval in leopard geckos (Eublepharis macularius)

Background: Leopard geckos (Eublepharis macularius) are a popular captive bred species of reptile in the exotic pet trade that are commonly seen for clinical presentations consistent with hypovitaminosis A. There has been a lack of antemortem diagnostics available for minimally invasive and appropriate diagnosis of this disease. Reference intervals for retinol have not been published or validated in leopard geckos or any closely related species. Methods: Plasma, with a sample volume of only 50 mu l, from 40 healthy captive bred leopard geckos, 20 males and 20 females were analyzed using ultra-high-performance liquid chromatography with tandem mass spectrometry (UPLC-MS/MS) to determine plasma retinol concentrations. Results: Using UPLC/MS analysis data was normally distributed and a reference interval for plasma retinol in the leopard gecko was 0.06 to 0.55 mu g/mL (0.01-0.08 mu mol/L). A mean of 0.31 mu g/mL with a lower limit 95% confidence interval being 0.03 to 0.10 mu g/mL and upper limit of 0.52 to 0.59 mu g/mL. No significant variations of plasma retinol were found based on gecko color morph, age or weight. Female leopard geckos had a slightly higher mean plasma retinol compared to males, but was not significantly different. Conclusions and clinical relevance: This study will allow veterinary clinicians to better diagnose and treat hypovitaminosis A and to provide advice on dietary supplementation and dietary improvement for the leopard gecko and possibly other gecko species as well. In addition, these values can be used to design and evaluate other studies for nutritional needs of this species. Limitations of this study include only a single season of collection, no same time comparison to liver values, and the evaluation of only captive bred individuals.