Table 2 FT4 and FT3 reference intervals derived using different laboratory instruments in children with TSH concentration 0.5–2.5 mIU/L.
Statistical Parameters | FT4, pmol/L | FT3, pmol/L | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
DxI 800 | Centaur | Vitros 5600 | Cobas | Architect | DxI 800 | Centaur | Vitros 5600 | Cobas | Architect | |
TSH < 0.5 mIU/L, n excluded | 11 | 11 | 12 | 11 | 12 | 11 | 11 | 12 | 11 | 12 |
TSH > 2.5 mIU/L, n excluded | 21 | 19 | 24 | 22 | 14 | 21 | 19 | 24 | 22 | 14 |
Outlier by Reeds test | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Final n | 28 | 30 | 24 | 27 | 34 | 28 | 30 | 24 | 27 | 34 |
Normality by Shapiro-Wilk test | Accept | Accept | Accept | Accept | Accept | Reject | Accept | Accept | Accept | Accept |
Transformation | None | None | None | None | None | Logarithmic | None | None | None | None |
Minimum | 10.4 | 12.8 | 11.7 | 15.2 | 11.2 | 4.9 | 4.2 | 4.9 | 4.2 | 3.8 |
Maximum | 17.5 | 23.2 | 23.1 | 25.4 | 19.2 | 8.7 | 7.3 | 8.9 | 7.0 | 7.0 |
Mean | 14.0 | 17.9 | 18.0 | 20.8 | 15.8 | 6.4 | 5.7 | 6.7 | 5.7 | 5.1 |
Median | 14.1 | 18.2 | 18.4 | 21.0 | 15.8 | 6.1 | 5.9 | 6.8 | 5.9 | 5.1 |
SD | 1.7 | 2.2 | 2.7 | 2.6 | 1.8 | NA | 1.0 | 0.7 | 0.7 | |
Reference intervals (normal) | ||||||||||
Lower limit (2.5th percentile) | 10.6 | 13.6 | 12.6 | 15.8 | 12.2 | 4.7 | 4.3 | 4.7 | 4.4 | 3.7 |
90% CI | 9.6 to 11.5 | 12.5 to 14.8 | 11.0 to 14.2 | 14.4 to 17.2 | 11.3 to 13.1 | 4.3 to 5.1 | 3.9 to 4.7 | 4.1 to 5.3 | 4.0 to 4.8 | 3.4 to 4.1 |
Upper limit (97.5th percentile) | 17.4 | 22.2 | 23.4 | 25.8 | 19.3 | 8.7 | 7.2 | 8.8 | 7.1 | 6.4 |
90% CI | 16.4 to 18.3 | 21.0 to 23.4 | 21.8 to 25.0 | 24.4 to 27.2 | 18.4 to 20.2 | 8.0 to 9.5 | 6.8 to 7.6 | 8.1 to 9.4 | 6.7 to 7.5 | 6.1 to 6.7 |
Robust method (CLSI C28-A3) | ||||||||||
Lower limit | 10.5 | 13.4 | 12.7 | 15.7 | 12.2 | 4.4 | 4.2 | 4.5 | 4.4 | 3.6 |
90% CI | 9.4 to 11.5 | 12.1 to 14.7 | 10.5 to 14.6 | 14.1 to 17.3 | 11.2 to 13.2 | 4.1 to 4.8 | 3.8 to 4.7 | 3.9 to 5.2 | 3.9 to 4.9 | 3.3 to 4.0 |
Upper limit | 17.8 | 22.5 | 24.4 | 26.4 | 19.8 | 8.7 | 7.4 | 8.9 | 7.3 | 6.5 |
90% CI | 16.7 to 18.6 | 21.2 to 23.7 | 22.6 to 25.9 | 24.9 to 27.7 | 18.8 to 20.6 | 7.8 to 9.8 | 7.01 to 7.8 | 8.3 to 9.5 | 6.9 to 7.7 | 6.1 to 6.8 |
