Newborn Screening (NS) program for congenital hypothyroidism (CH) has completely changed the natural history of this devastating disorder for the vast majority of children with CH. However, cases of missed CH do happen, and it is important to keep this possibility in mind during every day clinical practice. The objective of this study was to analyze the recognized cases of undiagnosed CH by the NS program in Central Serbia in order to evaluate the reasons for such omissions. Data regarding the recognized missed cases of CH between the years of 1983 and 2013 were collected and analyzed. During 30 years of the NS program for CH on the territory of Central Serbia, 1,547,122 newborns were screened, and during this period, 14 children with CH were missed by the NS. Five missed cases were children with athyreosis (35.8%), 8 had ectopic thyroid gland (57.1%) and one child had dyshormonogenesis (7.1%). The median age at diagnosis of CH in these missed cases was 1.12 years (range 0.08-13.5 years). In the group of children with missed diagnosis of CH, 71.4% were missed due to errors during sample collection, and 28.6% of patients were missed due to false negative screening results. Continuous education of neonatologists as well as nurses in neonatal units of maternity hospital are necessary to avoid errors in sample collection. It is of high importance to notice in a discharge list if a child is referred to the hospital before the sample is taken in a maternity hospital. On the other hand, the maternity hospital has to inform the screening laboratory about any child who was referred to another hospital if the blood samples for screening are not taken. Parents should be better informed that each child has to be included in the NS which is obligatory in Serbia. In addition, awareness amongst pediatricians in primary care should be raised regarding the possibility of missed cases of CH.

Keywords: congenital hypothyroidism, missed cases, newborn screening program