EXPRESS: Serum vitamin D metabolites do not differ between cats with chronic kidney disease and healthy cats

Objective: To characterize comprehensive vitamin D metabolite profiles in cats with chronic kidney disease (CKD) compared to healthy cats. Methods: Thirty-three healthy cats and 66 cats with CKD (6 IRIS Stage 1, 36 IRIS Stage 2, 18 IRIS Stage 3, 6 IRIS Stage 4) were prospectively enrolled. Serum vitamin D metabolites, including 25-hydroxyvitamin D3 (25[OH]D3), 3-epi-25-hydroxyvitain D3 (3-epi-25[OH]D3), 1,25-dihydroxyvitamin D3 (1,25[OH]2D3; calcitriol), and 24,25-dihydroxyvitamin D3 (24,25[OH]2D3) were analyzed via LC-MS/MS. Vitamin D metabolites, clinicopathologic parameters, age, body weight and body condition score were compared between groups using a Mann Whitney test or t test as appropriate. Correlations between Vitamin D metabolites and clinicopathologic parameters, age and weight were assessed using Spearman rank test. Results: There was no significant difference in any vitamin D metabolite between groups. Median (range) 25(OH)D3 concentrations in cats with CKD and healthy cats were 28.9 ng/mL (12.2-68.8) and 26.3 ng/mL (11.5-55.9), respectively. Median (range) 3-epi-25(OH)D3 concentrations in cats with CKD and healthy cats were 9.1 ng/mL (2.2-30.4) and 7.2 ng/mL (1.9-22.9), respectively. Median (range) calcitriol concentrations in cats with CKD and healthy cats were 141.3 pg/mL (38.6-367.8) and 127.9 pg/mL (71.5-235.8), respectively. Median (range) 24,25(OH)2D3 concentrations in cats with CKD and healthy cats were 9.8 ng/mL (2.5-32.5) and 8.8 ng/mL (1.2-38.4) respectively. There was no correlation between any vitamin D metabolite and age or serum creatinine concentration, and no correlation between 25(OH)D and hematocrit, blood pressure, or urine protein:creatinine ratio. Conclusions and relevance: Vitamin D metabolites were not significantly different in cats with CKD which could have implications for recommendations regarding calcitriol supplementation.