Evaluation of two immunoassays for the measurement of human chorionic gonadotropin in urine for anti-doping purposes.
BACKGROUND
Urinary human chorionic gonadotropin (hCG) concentration is routinely measured in all anti-doping laboratories to exclude the misuse of recombinant or urinary hCG preparations. In this study, extended validation of two commercial immunoassays for hCG measurements in urine was performed. Both tests were initially designed for hCG determination in human serum/plasma.


METHODS
Access and Elecsys 1010 are two automated immunoanalysers for central laboratories. The limits of detection and quantification, as well as intra-laboratory and inter-technique correlation, precision, and accuracy, were determined. Stability studies of hCG in urine following freezing and thawing cycles (n = 3) as well as storage conditions at room temperature, 4 degrees C and -20 degrees C, were performed.


RESULTS
Statistical evaluation of hCG concentrations in male urine samples (n = 2429) measured with the Elecsys 1010 system enabled us to draw a skewed frequency histogram and establish a far outside value equal to 2.3 IU/L. This decision limit corresponds to the concentration at which a sportsman will be considered positive for hCG. Intra-assay precision for the Access analyser was less than 4.0%, whereas the inter-assay precision was closer to 4.5% (concentrations of the official external controls contained between 5.5 and 195.0 IU/L). Intra and interassay precision for the Elecsys 1010 analyser was slightly better. A good inter-technique correlation was obtained when measuring various urine samples (male and female). No urinary hCG loss was observed after two freeze/thaw cycles. On the other hand, time and inappropriate storage conditions, such as temperatures above 10 degrees C for more than 5 days, can deteriorate urinary hCG.


CONCLUSIONS
Both analysers showed acceptable performances and are suitable for screening urine for anti-doping analyses. Each laboratory should validate and establish its own reference values because hCG concentrations measured in urine can be different from one immunoassay to another. The time delay between urine collection and analysis should be reduced as much as possible, and urine samples should be transported in optimal conditions to avoid a loss of hCG immunoreactivity.
Robinson
Neil
N
Laboratoire Suisse d'Analyse du Dopage, Centre Universitaire Romand de Médecine Légale, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Epalinges, Switzerland. Neil.Robinson@chuv.ch
Sottas
Pierre-Edouard
PE
Saugy
Martial
M
D056352:Athletes / Q000706:statistics & numerical data; D001331:Automation; D006063:Chorionic Gonadotropin / Q000652:urine*; D004300:Doping in Sports / Q000706:statistics & numerical data*; D004355:Drug Stability; D005615:Freezing; D006801:Humans; D007118:Immunoassay / Q000379:methods; D007753:Laboratories / Q000592:standards; D008297:Male; D008403:Mass Screening / Q000379:methods; D011994:Recombinant Proteins / Q000652:urine; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D006063:Chorionic Gonadotropin; D011994:Recombinant Proteins