Multianalyte LC-MS-based methods in doping control: what are the implications for doping athletes?

Over the last 50 years, the list of doping substances and methods has been progressively expanding, being regularly reviewed by the international antidoping authorities (formerly the Medical Commission of the International Olympic Committee, and afterward, following its constitution in 1999, the World Anti-Doping Agency [WADA]). New substances/classes of substances have been periodically included in the list, keeping the pace with more advanced and sophisticated doping trends. At present, and apart from the prohibited performance enhancing and masking methods (e.g., blood transfusions and tampering strategies), the list comprises several hundreds of biologically active substances, with broad differences in their physicochemical properties (i.e., molecular weight, polarity and acid-basic properties) [1]. As a consequence, the ‘one class – one procedure’ approach, which had been followed by nearly all accredited antidoping laboratories worldwide until the turn of the millennium, is no longer sustainable. The need to minimize the overall number of independent analytical procedures, and, in parallel, to reduce the analytical costs, stimulated the development of multitargeted methods, aimed to increase the overall ratio of ‘target analytes: procedure’ [2–6]. The above evolution has not always been a straight forward process. The need to comply with the WADA technical requirements (both in terms of identification criteria and of minimum required performance limits [7,8]) and with the reduction of the reporting time (a constraint that becomes even more critical during international sport events, where the daily workload also drastically increases) has imposed a thorough re-planning of the analytical procedures. The development of an antidoping analytical method requires the appropriate knowledge not only of the biophysicochemical properties of the target analyte, but also of its PK profile. Historically, immunological methods and GC-based techniques were applied in antidoping science, as preferential screening methods for the detection of prohibited substances, which were originally limited to nonendogenous stimulants and narcotics. In the 1980s, GC–MS became the reference analytical platform for the detection and quantification of the majority of the low molecular weight doping substances [3–6]. In the following two decades, with the inclusion in the Prohibited List of new classes of low molecular weight, hydrophilic, thermolabile, nonvolatile analytes (including, but not limited to, glucocorticoids and designer steroids) and simultaneously of peptide hormones, scientists were obliged to design, develop, validate and apply techniques based on LC–MS/MS.