Correlation between LC–MS/MS and ELISA methods for quantitative analysis of desmosine-containing solutions

Background: Desmosine and isodesmosine are crosslinking amino acids found in extracellular matrix protein elastin, which imparts elasticity to tissues such as those of the lungs and arteries. These compounds are promising biomarkers for diseases involving elastin degradation, such as chronic obstructive pulmonary disease.

Research design and method: This study examined the correlation between isotope-dilution LC–MS/MS and a newly established ELISA for in vitro diagnosis using a variety of samples.

Results: Results of ELISA and LC–MS/MS analyses exhibited a high correlation coefficient (0.9941). However, whereas the LC–MS/MS measurements deviated approximately 2-fold from the theoretical values, the ELISA measurements ranged from 0.83 to 1.06 (avg 0.94) times the theoretical values. Precise measurement of the absorbance of synthetic desmosine revealed a molar extinction coefficient of 2403, which differed markedly from the previously reported value of 4900 in 1963. Using this value to recalculate the amount of added desmosine, the LC–MS/MS measurements were 0.68 to 0.99 (avg 0.87) times the theoretical values.

Conclusion: Thus, the developed ELISA enables highly accurate determination of desmosine concentrations, comparable to LC–MS/MS, suggesting that ELISA is a potentially useful in vitro diagnostic tool.