Performance characteristics of two immunoassays for the measurement of urinary luteinizing hormone

Abstract

Urine luteinizing hormone (LH) concentration is routinely measured in all anti-doping laboratories to exclude recombinant LH abuse and to test any potential alteration of the hypophyseal-gonadal axis. Before establishing proper reference values among professional top level athletes, an extended validation of two commercial immunoassays for LH measurements was performed. Elecsys ® 1010 and Access ® are two automated immunoanalyzers for central laboratories. The limit of detection, the limit of quantification, intra-laboratory, inter-technique correlation, precision, accuracy were determined. Furthermore, reference urinary LH distribution values for male and female top level athletes were determined. Stability studies of LH in urine following freezing and thawing cycles ( n = 3) as well as storage conditions at room temperature, 4 °C and −20 °C were performed. Male and female subjects showed important urinary corrected (specific gravity correction) LH distribution differences. Intra-assay precision for the Access ® analyzer was less than 8.0% whereas inter-assay was close to 11%. Intra and inter-assay precision for the Elecsys ® 1010 analyzer was slightly better. A good inter-technique correlation was obtained ([Elecsys ® 1010] = 1.0434[Access ®] + 1.146, R = 0.953). No urinary LH loss was observed after two freezing and thawing cycles. On the other hand, time and bad storage conditions such as elevated temperature can deteriorate rapidly urinary LH. In conclusion, both analyzers showed acceptable performances and are suitable for screening anti-doping analyses. Each anti-doping laboratory has to settle its own reference distribution values and then determine when to launch a confirmation procedure. This takes place then depending on the positivity criteria the anti-doping laboratory has established and validated. This study also clearly showed that the time delay between the urine collection and the analysis should be reduced as much as possible and urine samples should be transported in optimal conditions (low temperature and quickly) to decrease urinary LH deterioration.