VDI utilizes the gold-standard in Parathyroid Hormone testing: PTH 1-84. Unlike intact PTH (iPTH), VDI measures the entire PTH sequence (84 amino acids) with no fragment interference that is common with intact PTH; particularly the 7-34 fragment which often accumulates in renal disease. The assay is a sandwich chemiluminescent immunoassay that is run on a fully automated analyzer, validated for use in dogs, cats, and horses with serum.