Comparison of manufacturer’s RIs for TSH, T3, and FT4
| A | B | C | |
|---|---|---|---|
| Instrument (manufacturer) | Architect i2000 (Abbott Diagnostics) | DxI 800 (Beckman Coulter Diagnostics) | Cobas e801 (Roche Diagnostics) |
| Principle | Chemiluminescence microparticle immunoassay | Paramagnetic particle chemiluminescence immunoassay | Electrochemiluminescence immunoassay |
| Reference material | |||
| TSH | WHO 2nd IS 80/558 | WHO 3rd IS 81/565 | WHO 2nd IS 80/558 |
| T3 | Triiodo-L-thyroxine solution (CRM) | USP reference material liothyronine | Reference standards by weighing T3 into analyte-free human serum matrix |
| FT4 | Internal reference standard | Manufacturer’s working calibrator traceable to USP reference material | Standardized against the Enzymun FT4 test over a chain of Elecsys FT4 generations |
| Manufacturer’s RI (unit) | |||
| TSH (μIU/mL) | 0.35–4.94 (99 percentiles from 549 individuals defined as normal by the AxSYM ultrasensitive hTSH II and AxSYM FT4 assays) | 0.38–5.33 (97.5 percentiles from 393 healthy euthyroid adults) | 0.27–4.2 (95 percentiles from 516 healthy subjects) |
| T3 (ng/mL) | 0.64–1.52 (95 percentiles from 260 individuals determined as normal by ARCHITECT anti-Tg, anti-TPO, and TSH assays) | 0.87–1.78 (95 percentiles from 239 ambulatory subjects) | 0.8–2.0 (95 percentiles from 514 healthy subjects) |
| FT4 (ng/dL) | 0.70–1.48 (99 percentiles from 411 individuals determined as normal by AxSYM ultrasensitive hTSH II and AxSYM FT4 assays) | 0.61–1.12 (95 percentile from 316 subjects with TSH value 0.3–3.0 μIU/mL) | 0.93–1.70 (95 percentiles from 801 healthy subjects) |
Abbreviations: RI, reference interval; TSH, thyroid stimulating hormone; T3, triiodothyronine; FT4, free thyroxine; WHO, World Health Organization; IS, international standard; CRM, certified reference material, USP, United State Pharmacopeia.