Sex hormone binding globulin: The importance of establishing sex-based reference values.

OBJECTIVES:Assay of sex hormone binding globulin (SHBG), the main carrier protein for sexual steroids, is prescribed mainly by endocrinologists and performed in specialized laboratories. This study aimed to evaluate the analytic performance of an automated immunochemiluminescent assay (ImmunoDiagnostic Systems (IDS), Boldon, United Kingdom) compared to a manual radioimmunoassay (Cisbio Bioassays, Codolet, France). It further aimed to assess the suitability of the reference values proposed by IDS. MATERIALS AND METHODS:One hundred and forty sera were used to assess the analytic performance of the IDS kit. The coefficients of variation (CV%) for within- and between-run precision were calculated. The reference values provided by IDS were recalculated based on the regression curve equation obtained by comparing the IDS and Cisbio values on Passing-Bablok regression. The new sex-based reference values were then established and their concordance with clinical status was evaluated on Kappa coefficient. RESULTS:The new kit correlated strongly with the reference technique (R2=0.96). Based on the regression line equation, the new reference values for IDS were [20.9-50.6] nmol/L for men and [33.8-71.1] nmol/L for women. Agreement with the reference values we established was 0.933 for men and 0.825 for women, compared with 0.606 and 0.286 for the supplier's values. CONCLUSION:The performance of the IDS kit met the current recommendations and correlated strongly with the Cisbio method. The calculation of new sex-based reference values was needed to correctly classify patients according to androgen status, underlining the importance of systematically checking the reference values provided by suppliers.