TY - JOUR
T1 - Quantification of serum 1-84 parathyroid hormone in patients with hyperparathyroidism by immunocapture in situ digestion liquid chromatography-tandem mass spectrometry
AU - Kumar, Vivek
AU - Barnidge, David R.
AU - Chen, Li Sheng
AU - Twentyman, Jolaine M.
AU - Cradic, Kendall W.
AU - Grebe, Stefan K.
AU - Singh, Ravinder J.
PY - 2010/2/1
Y1 - 2010/2/1
N2 - BACKGROUND: Immunoassays specific for 1-84 parathyroid hormone (PTH) reportedly reflect the bioactivity of PTH; however, PTH immunoassays can be susceptible to interference by cross-reacting PTH fragments. In addition, these assays currently lack standardization. Amethodology using immunocapture purification with liquid chromatography-tandem mass spectrometry (LC-MS/MS) detection, along with a stable isotope-labeled internal standard, may help address these issues. METHODS: We isolated 1-84 PTH from 1 mL serum by immunocapture on a 6.5-mm polystyrene bead. The immobilized PTH was digested in situ and analyzed by LC-MS/MS. For quantification, we used the selected reaction monitoring response from the N-terminal tryptic peptide 1-13 PTH (1SVSEIQLMHNLGK13). RESULTS: The linear range of the assay was 39.1-4560 ng/L, and the limit of detection and limit of quantification were 14.5 ng/L and 39.1 ng/L, respectively. The intraassay CVs ranged from 6% to 11%, and the interassay CVs ranged from 7% to 17%. Interference by PTH fragments 1-44 PTH, 7-84 PTH, 43-68 PTH, 52-84 PTH, 64-84 PTH, and PTH-related protein (PTHrP) was ≤1% to ≤0.001%.Method comparison of LC-MS/MS vs the Roche Cobas® immunoassay yielded Deming fit of LC-MS/MS = 1.01x immunoassay - 13.21. The mean bias by Bland-Altman plot was -9.4%. CONCLUSIONS: In patients with hyperparathyroidism, the immunocapture in situ digestion LC-MS/MS method can provide accurate and precise PTH results compared with immunoassay.
AB - BACKGROUND: Immunoassays specific for 1-84 parathyroid hormone (PTH) reportedly reflect the bioactivity of PTH; however, PTH immunoassays can be susceptible to interference by cross-reacting PTH fragments. In addition, these assays currently lack standardization. Amethodology using immunocapture purification with liquid chromatography-tandem mass spectrometry (LC-MS/MS) detection, along with a stable isotope-labeled internal standard, may help address these issues. METHODS: We isolated 1-84 PTH from 1 mL serum by immunocapture on a 6.5-mm polystyrene bead. The immobilized PTH was digested in situ and analyzed by LC-MS/MS. For quantification, we used the selected reaction monitoring response from the N-terminal tryptic peptide 1-13 PTH (1SVSEIQLMHNLGK13). RESULTS: The linear range of the assay was 39.1-4560 ng/L, and the limit of detection and limit of quantification were 14.5 ng/L and 39.1 ng/L, respectively. The intraassay CVs ranged from 6% to 11%, and the interassay CVs ranged from 7% to 17%. Interference by PTH fragments 1-44 PTH, 7-84 PTH, 43-68 PTH, 52-84 PTH, 64-84 PTH, and PTH-related protein (PTHrP) was ≤1% to ≤0.001%.Method comparison of LC-MS/MS vs the Roche Cobas® immunoassay yielded Deming fit of LC-MS/MS = 1.01x immunoassay - 13.21. The mean bias by Bland-Altman plot was -9.4%. CONCLUSIONS: In patients with hyperparathyroidism, the immunocapture in situ digestion LC-MS/MS method can provide accurate and precise PTH results compared with immunoassay.
UR - http://www.scopus.com/inward/record.url?scp=75749111711&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=75749111711&partnerID=8YFLogxK
U2 - 10.1373/clinchem.2009.134643
DO - 10.1373/clinchem.2009.134643
M3 - Article
C2 - 20007860
AN - SCOPUS:75749111711
SN - 0009-9147
VL - 56
SP - 306
EP - 313
JO - Clinical chemistry
JF - Clinical chemistry
IS - 2
ER -