Patent ID: 8349613

Claim:
A mass spectroscopy method for monitoring a vitamin D replacement therapy in a mammalian patient comprising: a) obtaining a biological sample from the mammalian patient, wherein the mammalian patient has received at least one dose of a vitamin D replacement therapy; b) determining an amount of 25-hydroxyvitamin D2 in a sample derived from the mammalian patient's biological sample, wherein the determining comprises using a mass spectrometry technique to detect underivatized 25-hydroxyvitamin D2, wherein the mass spectrometry technique comprises a LC-MS/MS technique and wherein the LC-MS/MS technique comprises the use of a triple quadrupole instrument in Multiple Reaction Monitoring (MRM), positive ion mode; and c) comparing the amount of 25-hydroxyvitamin D2 in the sample with a range for 25-hydroxyvitamin D2 expected for the replacement therapy, wherein a lower than expected amount of 25-hydroxyvitamin D2 relative to the range expected is indicative of patient non-compliance with the therapy, malabsorption of vitamin D supplements, or resistance to 25-hydroxyvitamin D2.