RESUMEN
BACKGROUND: The FREND™ thyroid stimulating hormone (TSH) and free thyroxine (FT4) assays are newly developed rapid quantitative immunoassays utilizing antibody-conjugated fluorescent nanoparticles in a microfluidic flow system. The FREND system is a simple and portable fluorescence reader with rapid turnaround time (4 - 10 minutes). METHODS: The analytical sensitivity, precision, and linearity were evaluated. For the method comparison, FREND TSH and FT4 levels were compared with those from ADVIA Centaur XP and Abbott ARCHITECT i2000. RESULTS: The limit of detection was 0.047 mIU/L and 5.031 pmol/L in FREND TSH and FT4 assays. FREND system had acceptable linearity and precision of ï£ 10% across the assay range (0.05 - 25.0 mIU/L for TSH and 1.4 - 96.8 pmol/L for FT4). The functional sensitivity was 0.057 mIU/L for the TSH assay and 4.644 pmol/L for the FT4 assay. Passing-Bablok regression analysis of TSH data showed good correlation among the three assays. For the FT4 assay, FREND FT4 displayed good correlation with the ARCHITECT FT4 assay, but the intercepts and slopes significantly differed between FREND and Centaur results: [FREND FT4] = 4.799 + 0.600 [Centaur FT4]. CONCLUSIONS: The analytical performance of FREND TSH and FT4 assays was satisfactory for use in the clinical laboratory. The FREND FT4 assay was in concordance with ARCHITECT FT4, but it needs further investigation and harmonization.