Table 2. Changes in TSH cutoff values in the Turkish National NSP .

Starting date	Borderline TSH cutoff†	High TSH cutoff†	Reporting unit*
December 2006	20 mU/L	50 mU/L	Serum
July 2008	15 mU/L	50 mU/L	Serum
February 2013	5.5 mU/L	20 mU/L	Whole blood*

^†When TSH level is between the borderline and high cutoff points, screening is repeated. When TSH level is above the high cutoff or repeat screening is abnormal, venous sampling is performed for confirmatory testing.

*Filter-paper TSH screening results can be reported per unit of serum or whole blood. Serum equivalent is calculated as 2.2 times the whole blood TSH value, assuming an average hematocrit of 55% for the first days of life. Therefore, a borderline TSH cutoff of 5.5 mU/L whole blood is equivalent to 12 mU/L in serum.

NSP: newborn screening program, TSH: thyroid-stimulating hormone