When is a sample a urine sample? Markers for urine sample authenticity assessment in sports drug testing

Human routine doping controls rely to a considerable extent on urine samples, and test methods have been optimized for decades to allow for comprehensive analyses with adequate analytical sensitivities. However, attempts of sample manipulation, presumably in order to escape an adverse analytical finding, were reported to include adulteration as well as substitution, which has revived the debate as to when a sample submitted as urine specimen for sports drug testing purposes is, indeed, to be considered as 'urine.' In consideration of selected case reports as well as analytical parameters routinely acquired with doping control urine samples, options concerning guidance in that context are discussed, as detecting and reporting urine substitution and urine adulteration require laboratory approaches that might differ considerably from protocols applied for, e.g. the confirmation of the presence of a prohibited substance. In particular, commonly monitored markers characterizing urinary specifics such as pH, specific gravity, and the presence of a human urinary steroid profile and 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) in established reference ranges could assist in defining acceptance criteria for urine samples and, thereby, guidelines when a specimen does not qualify as human urine.