Assay for Monitoring Parathyroid Hormone (PTH) Variants by Tandem Mass Spectrometry

Abstract

Methods are described for monitoring the amounts of PTH variants in a biological sample by digesting the sample to produce surrogate peptides specific to the targeted PTH variants, and detecting and quantifying the surrogate peptides by selective reaction monitoring (SRM) mass spectrometry, using a set of precursor-to-product ion transitions optimized for sensitivity and selectivity. The PTH variants, or a portion thereof, may be concentrated in the sample by means of immunoaffinity capture or other suitable technique. The mass spectrometric method described herein enables the concurrent measurement of peptides representative of a plurality of targeted PTH variants in a single assay.

What is claimed is: 
     
         1 . A method for diagnosing renal failure, comprising:
 obtaining a biological sample, the biological sample being selected from a group consisting of blood serum and blood plasma;   proteolytically digesting the biological sample;   determining by SRM mass spectrometry the amount of at least one PTH peptide present in the biological sample, wherein the at least one PTH peptide comprises at least one of LQDVHNFVALGAPLAPR (SEQ ID NO.: 8), SVSEIQLMHNLGK (SEQ ID NO.: 7), HLNSMER (SEQ ID NO.: 1), FVALGAPLAPR (SEQ ID NO.: 6) and ADVNVLTK (SEQ ID NO.: 5); and   comparing the determined amount of the at east one. PTH peptide to a correspond mg control value.   
     
     
         2 . The method of  claim 1 , wherein the at least one PTH peptide comprises LQDVHNFVALGAPLAPR (SEQ ID NO.: 8). 
     
     
         3 . The method of  claim 2 , wherein the step of determining by SRM mass spectrometry the amount of at least one PTH peptide comprises monitoring at least one precursor-to-product ion transition selected from a group consisting of m/z 607→681, 607→553 and 607→569. 
     
     
         4 . The method of  claim 1 , wherein the at least one PTH peptide comprises SVSEIQLMHNLGK (SEQ ID NO.: 7). 
     
     
         5 . The method of  claim 4 , wherein the step of determining by SRM mass spectrometry the amount of at least one PTH peptide comprises monitoring at least one precursor-to-product ion transition selected from a group consisting of m/z 486→636 and 486→684. 
     
     
         6 . The method of  claim 1 , wherein the at least one PTH peptide comprises ADVNVLTK (SEQ ID NO.: 5). 
     
     
         7 . The method of  claim 6 , wherein the step of determining by SRM mass spectrometry the amount of at least one PTH peptide comprises monitoring at least one precursor-to-product ion transition selected from a group consisting of m/z 430→361, 287→361, 430→460 and 287→460. 
     
     
         8 . The method of  claim 1 , wherein the at least one PTH peptide comprises at least two of LQDVHNFVALGAPLAPR (SEQ ID NO.: 8), SVSEIQLMHNLGK (SEQ ID NO.: 7), HLNSMER (SEQ ID NO.: 1), FVALGAPLAPR (SEQ ID NO.: 6) and ADVNVLTK (SEQ ID NO.: 5). 
     
     
         9 . The method of  claim 1 , wherein the step of determining by SRM mass spectrometry the amount of at least one PTH peptide includes concentrating the at least one PTH peptide by immunoaffinity capture. 
     
     
         10 . The method of  claim 1 , wherein the step of determining by SRM mass spectrometry the amount of at least one PTH peptide includes adding at least one internal reference standard to the biological sample.