Distribution of TSH, T3, and FT4 values measured using three automated immunoassay analyzers in EQA samples
| Method | No. | Mean±SD | Median (IQR) | Min | Max |
|---|---|---|---|---|---|
| TSH (RI, unit μIL/mL) | |||||
| A (0.35–4.94) | 3,924 | 9.11±9.94 | 4.70 (0.72–20.70) | 0.05 | 35.02 |
| B (0.38–5.33) | 989 | 10.25±11.44 | 5.10 (0.71–22.10) | 0.05 | 35.07 |
| C (0.27–4.20) | 6,605 | 11.68±13.08 | 6.03 (0.90–23.86) | 0.01 | 43.52 |
| T3 (RI, unit ng/mL) | |||||
| A (0.64–1.52) | 3,467 | 1.79±0.913 | 1.68 (0.9–2.52) | 0.04 | 4.46 |
| B (0.87–1.78) | 946 | 2.00±1.01 | 1.87 (1–2.8) | 0.25 | 4.81 |
| C (0.8–2.0) | 5,750 | 2.30±1.12 | 2.1 (1.21–3.13) | 0.45 | 9.7 |
| FT4 (RI, unit ng/dL) | |||||
| A (0.70–1.48) | 3,888 | 2.21±1.16 | 2.21 (0.95–3.09) | 0.62 | 9.40 |
| B (0.61–1.12) | 930 | 2.30±1.26 | 2.40 (0.82–3.36) | 0.53 | 5.18 |
| C (0.93–1.70) | 6,524 | 2.91±1.54 | 2.91 (1.28–4.07) | 0.69 | 7.77 |
Abbreviations: TSH, thyroid stimulating hormone; T3, triiodothyronine; FT4, free thyroxine; EQA, external quality assessment; SD, standard deviation; IQR, interquartile range (25th percentile–75th percentile); Min, minimum; Max, maximum; RI, reference interval.