Serum vitamin D metabolite and acute-phase protein concentrations are frequently abnormal in a cohort of hospitalized dogs and cats

OBJECTIVE To determine whether serum 25-hydroxyvitamin D (25[OH]D) and 1,25-dihydroxyvitamin D (1,25[OH] 2 D) concentrations are associated with survival and negatively correlate with acute-phase protein (APP) concentrations in ill dogs and cats admitted to nursing care units. ANIMALS Client-owned dogs (n = 79) and cats (16) admitted to 2 academic veterinary hospital nursing care units. METHODS A prospective cohort study was conducted between August 12, 2019, and October 26, 2021. A diagnostic laboratory measured 25(OH)D, 1,25(OH) 2 D, and haptoglobin (HPT) in dogs and cats; C-reactive protein (CRP) in dogs; and serum amyloid A (SAA) in cats. Serum was collected within 12 hours of admission. Illness severity (acute patient physiologic and laboratory evaluation [APPLE fast ]) scores and survival data were recorded. RESULTS Serum 25(OH)D concentrations were in the deficient range for 22 of 79 dogs and 2 of 16 cats. There were no associations between serum analyte concentrations (25[OH]D, 1,25[OH] 2 D, and APP) or APPLE fast score and survival in dogs or cats. In dogs, HPT was negatively correlated with 25(OH)D ( P = .002; r = –0.34) and 1,25(OH) 2 D ( P = .012; r = –0.28), while CRP was positively correlated with HPT ( P = .001; r = 0.32) and APPLE fast score ( P = .014; r = 0.16). In cats, 1,25(OH) 2 D was negatively correlated with APPLE fast scores ( P = .055; r = –0.49) and SAA was positively correlated with HPT ( P = .002; r = 0.73). CLINICAL RELEVANCE Serum 25(OH)D or 1,25(OH) 2 D was not associated with survival in our hospitalized patient population. Relationships between APP and serum vitamin D metabolites with APPLE fast scores in cats warrant further investigation as illness severity biomarkers.