CONGENITAL HYPOTHYROIDISM SCREENING AND THE CUTOFF FOR THYROTROPIN MEASUREMENT - RECOMMENDATIONS FROM THE NETHERLANDS

Objectives. There is little agreement as to the optimal cutoff point f or thyrotropin testing in primary thyroxine screening programs for con genital hypothyroidism. Most programs in the United States use a cutof f point of 10% of the lowest thyroxine values, whereas in the Netherla nds a cutoff point of 20% is used. Therefore, the results of the Dutch program may provide valuable information about the optimal cutoff poi nt. Methods. The frequency distribution of screening thyroxine values was studied in all cases of permanent primary congenital hypothyroidis m (n = 481) detected in 1 601 603 screened children born during the pe riod from January 1, 1981, to December 31, 1989, in the Netherlands. R esults. Programs using a 10% cutoff point would have missed 1.5% of ca ses. Above the 10% cutoff point, the marginal costs increase quite rap idly because of the escalating numbers of thyrotropin measurements nec essary to detect one case of permanent primary congenital hypothyroidi sm: 20 000 in the range of 11% to 15% and 40 000 in the range of 16% t o 20%. Conclusions. Based on these findings, a cutoff point of at leas t 10% is recommended.