Congenital hypothyroidism screening and the cutoff for thyrotropin measurement: recommendations from The Netherlands.

Abstract

There is little agreement as to the optimal cutoff point for thyrotropin testing in primary thyroxine screening programs for congenital hypothyroidism. Most programs in the United States use a cutoff point of 10% of the lowest thyroxine values, whereas in the Netherlands a cutoff point of 20% is used. Therefore, the results of the Dutch program may provide valuable information about the optimal cutoff point. The frequency distribution of screening thyroxine values was studied in all cases of permanent primary congenital hypothyroidism (n = 481) detected in 1,601,603 screened children born during the period from January 1, 1981, to December 31, 1989, in the Netherlands. Programs using a 10% cutoff point would have missed 1.5% of cases. Above the 10% cutoff point, the marginal costs increase quite rapidly because of the escalating numbers of thyrotropin measurements necessary to detect one case of permanent primary congenital hypothyroidism: 20,000 in the range of 11% to 15% and 40,000 in the range of 16% to 20%. Based on these findings, a cutoff point of at least 10% is recommended.