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

Abstract

The present invention relates to the use of 1,25-dihydroxyvitamin D values in ratio with PTH as a prognostic biomarker. More particularly, the present invention relates to 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. Levels of 1,25-dihydroxyvitamin D (1,25(OH)2D) are measured in a biological sample and taken together with parathyroid hormone (PTH) levels to provide a ratio indicative of the risk of worsening renal function.

What is claimed is: 
     
         1 . 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.   
     
     
         2 . The method according to  claim 1 , wherein said capture moiety is an antibody or an epitope-binding fragment thereof. 
     
     
         3 . The method according to  claim 2 , wherein said antibody is a monoclonal antibody. 
     
     
         4 . The method according to  claim 1 , wherein the predetermined threshold is comprised within the range of from 0.92 to 1.8. 
     
     
         5 . The method according to  claim 4 , wherein the predetermined threshold is 0.92, 0.98 or 1.68. 
     
     
         6 . The method according to  claim 1 , wherein 1,25-dihydroxyvitamin D and/or parathyroid hormone are detected and quantified using an immunoassay. 
     
     
         7 . The method according to  claim 6 , wherein the immunoassay is a chemiluminescent assay. 
     
     
         8 . The method according to  claim 6 , wherein 1,25-dihydroxyvitamin D is detected and quantified using an immunoassay which comprises:
 (i) contacting 1,25-dihydroxyvitamin D in said sample with a receptor protein comprising the Ligand Binding Domain of Vitamin D Receptor (VDR-LBD), thereby obtaining a first complex;   (ii) contacting said first complex with a capture moiety that specifically binds to a conformational epitope on said first complex, thereby obtaining a second complex; wherein said capture moiety does not specifically bind to either 1,25-dihydroxyvitamin D or VDR-LBD that is not bound in said first complex; and   (iii) detecting and quantifying said second complex as an indication of the amount of 1,25-dihydroxyvitamin D in the sample.   
     
     
         9 . The method according to  claim 8 , wherein said capture moiety is an antibody or an epitope-binding fragment thereof. 
     
     
         10 . The method according to  claim 9 , wherein said antibody is a monoclonal antibody. 
     
     
         11 . The method according to  claim 8 , wherein said capture moiety is immobilized on or to a solid support. 
     
     
         12 . The method according to  claim 8 , wherein said 1,25-dihydroxyvitamin D is detected and quantified using a sandwich immunoassay. 
     
     
         13 . The method according to  claim 12 , wherein in said step (ii) said capture moiety is detectably-labeled, and said step (iii) comprises detecting and quantifying detectably-labeled second complex. 
     
     
         14 . The method according to  claim 8 , wherein the predetermined threshold is comprised within the range of from 0.92 to 1.8. 
     
     
         15 . The method according to  claim 14 , wherein the predetermined threshold is 0.92, 0.98 or 1.68. 
     
     
         16 . The method according to  claim 8 , wherein parathyroid hormone is detected and quantified using an immunoassay. 
     
     
         17 . A method for determining the ratio of the concentration of 1,25-dihydroxyvitamin D to parathyroid hormone (PTH) in the serum, plasma or blood of a patient, wherein said method comprises:
 (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; 
   (b) assaying the concentration of parathyroid hormone (PTH) in said serum, plasma or blood; and   (c) determining the ratio of said determined concentration of 1,25-dihydroxyvitamin D to said assayed concentration of parathyroid hormone.   
     
     
         18 . The method according to  claim 17 , wherein said capture moiety is detectably-labeled. 
     
     
         19 . The method according to  claim 17 , wherein said capture moiety is an antibody or an epitope-binding fragment thereof. 
     
     
         20 . The method according to  claim 19 , wherein said antibody is a monoclonal antibody. 
     
     
         21 . The method according to  claim 17 , wherein 1,25-dihydroxyvitamin D and/or parathyroid hormone are detected and quantified using an immunoassay. 
     
     
         22 . The method according to  claim 21 , wherein said 1,25-dihydroxyvitamin D is detected and quantified using a sandwich immunoassay. 
     
     
         23 . The method according to  claim 21 , wherein the immunoassay is a chemiluminescent assay. 
     
     
         24 . The method according to  claim 17 , wherein said capture moiety is immobilized on or to a solid support.