Total Thyroxine Competitive Immunoassay for Thyroid Function & Neonatal Screening
The Sekbio TT4 CLIA Bulk Reagent enables quantitative measurement of Total Thyroxine (TT4 / Total T4) — the major secretory product of the thyroid gland. TT4 is essential for diagnosing hypothyroidism, hyperthyroidism, monitoring thyroid replacement therapy (levothyroxine), and neonatal thyroid screening programs where early T4 measurement prevents congenital hypothyroidism-related developmental delay.
Two-step competitive immunoassay on the AE chemiluminescence platform. Wide range 0–318.5 nmol/L, analytical LoD 0.048 nmol/L, and exceptional within-run CV of ≤1.95% at mid-range — enabling precise thyroid hormone level tracking for both diagnosis and treatment monitoring.
Two-step competitive: Step 1 — 30µL Rd + 30µL sample, 5 min (no wash); Step 2 — 30µL Ra + 30µL Rc, 5 min, wash; read RLU.
Inverse competitive response — RLU highest at 0 nmol/L (no competition) and lowest at 318.5 nmol/L. Signal-to-noise (S/N ratio blank/top) = 49.54.
| Calibrator (nmol/L) | RLU Run 1 | RLU Run 2 | RLU Run 3 | Avg RLU |
|---|---|---|---|---|
| 0 (Max signal) | 2,199,337 | 2,293,369 | 2,243,598 | 2,245,435 |
| 5.48 | 586,320 | 596,203 | 580,019 | 587,514 |
| 28.58 | 234,431 | 236,440 | 232,672 | 234,514 |
| 44.30 | 168,020 | 208,770 | 204,427 | 193,739 |
| 135.64 | 97,330 | 98,275 | 100,411 | 98,672 |
| 318.50 (Min signal) | 45,159 | 45,953 | 44,855 | 45,322 |
| S/N (0 nmol/L / 318.5 nmol/L) = 49.5. Analytical LoD = 0.048 nmol/L (blank mean + 2SD). | ||||
| QC Level (nmol/L) | Avg Conc (nmol/L) | SD | CV |
|---|---|---|---|
| 28.58 (Low) | 34.20 | 1.00 | 2.92% |
| 135.64 (Mid) | 126.52 | 2.46 | 1.95% |
| n=10 replicates per level. Acceptance criterion: CV ≤10%. Both levels meet criteria with large margin. | |||
TT4 is measured in neonatal blood spot screening programs for congenital hypothyroidism (CH) — the most common preventable cause of intellectual disability. Low TT4 triggers TSH confirmatory testing.
TT4 below reference range (<55 nmol/L) with elevated TSH confirms primary hypothyroidism. Elevated TT4 (>140 nmol/L) with suppressed TSH supports hyperthyroidism diagnosis.
Serial TT4 measurement during LT4 replacement therapy. CV ≤2% precision enables detection of meaningful concentration changes and dose adequacy assessment at 6–8 week intervals.
TT4 bulk reagent pair (Ra + Rc + Rd) for CLIA analyzer integration. Available paired with TT3, fT3, fT4 reagents for complete automated thyroid panel supply to analyzer manufacturers.
Technical datasheets, performance data, and OEM pricing available on request.