Endocrine Abstracts

Introduction: Radioactive assays are widely used in clinical laboratories for measuring free testosterone. The appearance of a non-isotopic, chemiluminescent automatic assay, may be an interesting alternative if the performance of the assay remains the same or higher.

Objective: To compare the free testosterone results by radioimmunoassay (RIA) and chemiluminescent assay (CLIA) and to analyze the clinical impact taking into account the % concordance.

Material and Methods: We studied 76 patients, aged 13–73 years old, and observed at CHLC medical appointments, in Lisbon. The serum samples were analyzed by “Free TESTO-RIA-CT”, DIASource (0.2–22.1 pg/ml) and “Maglumi Free Testosterone (CLIA)” Snibe (1.52–40.62 pg/ml). An excel tool was used for statistical treatment and the clinical concordance of the results were analyzed according to the reference values of both.

Results: A strong correlation was observed r=0.95 and linear regression was calculated: y=1.51x+0.072. The % concordance found was:

Conclusion: There is a good agreement between the two methods. The absence of age-stratified reference values by CLIA’ method may explain the discordant results. Despite the small sample size, Maglumi free testosterone may be considered a good alternative to the RIA assay, although it is fundamental to have reference values according to age and gender since the concentration of free testosterone varies throughout life from childhood to adulthood.