GI24 - Feasibility Study Using Undercarboxylated Osteocalcin as a Surrogate for Serum Vitamin-K in Chronic Enteropathy Dogs

Abstract: Background - Vitamin K deficiency has been described in chronic enteropathy, though evidence is sparse. Undercarboxylated osteocalcin (%ucOC) is the gold standard to assess vitamin K status in humans, but assays have not been validated in dogs.

Hypothesis/Objectives - To determine if commercially available enzyme immunoassays (EIAs) for undercarboxylated and carboxylated osteocalcin could be validated for use in dogs.

Animals - Previously banked canine serum was used.

Methods - EIAs for human undercarboxylated (Glu-) and carboxylated (Gla-) osteocalcin were performed according to the manufacturer’s instructions. Undercarboxylated recombinant canine osteocalcin (rcOC) was used to spike samples. Assay performance was determined by measuring percent recovery, linearity, and dilutional parallelism.

Results - Gla-OC and Glu-OC had a recovery of 73.3±0.9% and 77.1±10.7%, respectively, with acceptable linearity and dilutional parallelism. Intra-and inter-assay % coefficient of variation was 1.7±0.3% and 4.4-13.6%, respectively, for Gla-OC and 3.5±2.8% and 0.15±0.9% for Glu-OC. rcOC demonstrated excellent accuracy and dilutional parallelism for Gla-OC but could not be determined for Glu-OC due to concentrations near the low end of the detectable range.

Conclusions and clinical importance - Validation of the Glu- and Gla- assays shows that these EIAs could potentially be used in dogs, but further study is needed to correlate to vitamin K status.