Potential Pitfalls in Screening Programs for Congenital Hypothyroidism

Abstract

After completing this article, readers should be able to: 1. Delineate situations in which blood specimens for screening may be overlooked. 2. Describe the patterns of thyroid-stimulating hormone and thyroxine concentrations in very low-birthweight infants and the implications of these patterns for thyroid screening programs. For those of us involved in newborn screening, there is nothing more devastating than learning that the program did not detect an infant who has congenital hypothyroidism. After a moment of disbelief, we ask, “How did this happen and what should or could have been done to prevent such tragedy?” Moreover, in the typical scenario the misfortune frequently is compounded by failure of the clinician to make the clinical diagnosis in a timely fashion. Although these events are rare (probably less than one birth in 1 million), they should not be taken lightly. For the pediatrician, knowing where potential pitfalls lie might spare some future family from the needless anguish of a missed diagnosis. Slightly more than one quarter of a century ago a report emanating from Canada described a procedure for the measurement of thyroxine (T4) in dried blood on filter paper, opening the way for early detection and treatment of infants who have congenital hypothyroidism. Within a relatively short period of time, newborn screening programs for congenital hypothyroidism emerged in most of the industrialized nations, thereby relegating a major scourge of society to the status of a medical curiosity. At the outset, most screening programs were relatively primitive, lacking sophisticated data management systems and beset with technical and logistical problems. However, the manufacture of reliable assay materials and the introduction of automation coupled with online data reduction eventually improved these programs. Such improvements, together with growing experience in interpretating test results, overcame many of the drawbacks associated with early screening programs. Although most (but not …