Dimension LOCI Thyroid Stimulating Hormone Flex reagent cartridge (TSHL); Dimension LOCI Free Thyroxine Flex reagent cartridge (FT4L)

These are two reagent cartridges for the Dimension EXL chemistry analyzer with LOCI module that measure thyroid hormones. The TSHL cartridge quantifies Thyroid Stimulating Hormone (TSH) in serum and plasma to diagnose and monitor thyroid disease. The FT4L cartridge quantifies Free Thyroxine (FT4) in serum and plasma for the same clinical purpose.

Both devices use homogeneous, chemiluminescent immunoassay technology based on LOCI (Luminescence On a Chip Immunoassay) principles with synthetic bead reagents and direct light detection. The key modification from the predicates is enhanced biotin interference mitigation: the modified assays tolerate biotin up to 1200 ng/mL with ≤10% result change, compared to predicates tolerating only 250 ng/mL (TSHL) or 100 ng/mL (FT4L). Measuring intervals, sample types, calibrators, and operating principles remain identical to predicates.

CLSI EP17-A2 (detection capability), CLSI EP06-ED2 (linearity), CLSI EP09c (method comparison), CLSI EP05-A3 (precision/repeatability/reproducibility), CLSI EP34-ED1:2018 (dilution recovery), CLSI EP07-ED3 (interference testing), and CLSI EP28-A3C (reference range verification).

Substantial equivalence is established because the candidate devices have identical indications for use, analytes, sample types, measurement principles, technology, and instrument platform as their predicates (K081074 for TSHL, K073604 for FT4L). The only change—improved biotin interference resistance through modified assay components—does not alter the fundamental test principle or specificity to the analytes. Performance data across 145–146 patient samples, linearity studies, precision studies across multiple analyzers and reagent lots, and method comparison all demonstrate equivalence or superiority to predicates. Biotin tolerance improvement is clinically beneficial and does not compromise any other assay characteristic.