Sensitivity and specificity of different capillary TSH cut-off levels in predicting a venous fT4 of <10 pmol/L in 286 Scottish infants referred with capillary TSH elevation
| Capillary TSH cut-off (mU/L whole blood) | Sensitivity | Specificity |
|---|---|---|
| >10 | 0.987013 | 0.106061 |
| >20 | 0.961039 | 0.356061 |
| >30 | 0.922078 | 0.537879 |
| >35 | 0.902597 | 0.590909 |
| >40 | 0.902597 | 0.659091 |
| >45 | 0.883117 | 0.681818 |
| >50 | 0.857143 | 0.719697 |
| >60 | 0.831169 | 0.795455 |
| >70 | 0.818182 | 0.848485 |
| >80 | 0.792208 | 0.878788 |
| >90 | 0.75974 | 0.886364 |
| >100 | 0.746753 | 0.901515 |
| >110 | 0.74026 | 0.939394 |
| >120 | 0.694805 | 0.954545 |
Sensitivity refers to the proportion of infants with fT4 of <10 pmol/L whose capillary TSH is above a given cut-off value, while specificity refers to the proportion of infants with fT4 ≥10 pmol/L whose capillary TSH is below the cut-off value. fT4, free thyroxine; TSH, thyroid-stimulating hormone.