Abstract: This document relates to methods and materials involved in simultaneously determining (i.e., multiplexing) the levels of an analyte in biological samples from multiple subjects using high pressure liquid chromatography-tandem mass spectrometry (LC-MS/MS). For example, methods and materials for derivatizing vitamin D metabolites in samples obtained from multiple subjects (e.g., humans), and combining samples for simultaneous analysis in a single assay are provided.

Abstract: Methods for determining the amount of DHVD2 and/or DHVD3 in a sample are provided. The methods can employ LC-MS/MS techniques coupled with sample affinity purification and derivatization steps. Methods for diagnosing vitamin D deficiencies are also provided.

Abstract: This document provides methods and materials related to determining whether or not a mammal is receiving a steroid treatment. For example, methods and materials involved in assessing a biological sample (e.g., a urine sample) from a mammal for the presence or absence of a steroid or a steroid metabolite to determine whether or not the mammal is complying with a steroid treatment (e.g., a corticosteroid treatment for an allergic disease or asthma) are provided.