Table 1

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)SensitivitySpecificity
>100.9870130.106061
>200.9610390.356061
>300.9220780.537879
>350.9025970.590909
>400.9025970.659091
>450.8831170.681818
>500.8571430.719697
>600.8311690.795455
>700.8181820.848485
>800.7922080.878788
>900.759740.886364
>1000.7467530.901515
>1100.740260.939394
>1200.6948050.954545
  • 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.