A clinical biomarker assay for the quantification of d3-creatinine and creatinine using LC-MS/MS.
BACKGROUND
Current methods to measure skeletal muscle mass are not practical in a clinical setting. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods that measure the amount of urinary d3-creatinine enrichment after a single tracer dose of d3-creatine was developed.


RESULTS
The biomarkers d3-creatinine and creatinine were detected in human urine using LC-MS/MS. In this assay a surrogate analyte, d3-creatinine, was used to quantify endogenous creatinine. However, since endogenous concentrations of creatinine were orders of magnitude higher than d3-creatinine, the peak area of a less intense isotope of creatinine was acquired. A response factor is used to correct for using a less intense isotope multiple reaction monitoring transition.


CONCLUSIONS
Novel LC-MS/MS assays were developed that quantify the biomarkers d3-creatinine, creatinine and d3-creatine in urine. This method allows the estimation of total body creatine pool size and subsequent calculation of muscle mass. This assay was originally validated as fit-for-purpose and was followed by full validation.
GlaxoSmithKline, Research Triangle Park, NC 27709, USA.
Michael
M
Leonard
John
J
Dunn
Glenn
G
Smith
D015415:Biomarkers / Q000652:urine*; D002853:Chromatography, Liquid / Q000379:methods*; D003404:Creatinine / Q000378:metabolism*; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods*
D015415:Biomarkers; D003404:Creatinine