Use of 1,25-Dihydroxyvitamin D Values in Ratio with PTH as a Prognostic Biomarker

A method for predicting or stratifying the risk of worsening renal function (WRF) in a patient at risk of renal injury or affected by renal injury, the method comprising:

• (a) incubating a sample of serum or plasma or blood from said patient in a reaction container in the presence of a receptor protein comprising the Ligand Binding Domain of Vitamin D Receptor (VDR-LBD), and a capture moiety that specifically binds to a conformational epitope of VDR-LBD when said VDR-LBD is complexed with 1,25-dihydroxyvitamin D;
• wherein said complexing of VDR-LBD and 1,25-dihydroxyvitamin D does not naturally occur in serum, plasma or blood, and said capture moiety does not specifically bind to VDR-LBD or to 1,25-dihydroxyvitamin D that are not complexed with one another;
• and
• wherein said incubation is under conditions sufficient to permit the determination of the concentration of 1,25-dihydroxyvitamin D in said serum, plasma or blood;
• and
• (b) assaying the concentration of parathyroid hormone (PTH) in said serum, plasma or blood;
• wherein:
• when the [1,25-dihydroxyvitamin D]/[parathyroid hormone] ratio is above a predetermined threshold, the patient is predicted or stratified not to have an increased risk of worsening renal function, and
• when the [1,25-dihydroxyvitamin D]/[parathyroid hormone] ratio is below a predetermined threshold, the patient is predicted or stratified to have an increased risk of worsening renal function.