RESEARCH – September 2016

Expanded newborn screening by using tandem mass-spectrometry in Estonia: a review of 18-month’ experience

Authors: Karit Reinson, Ursula Ilo, Kadi Künnapas, Mari-Anne Vals, Kai Muru, Annika Kriisa, Katrin Õunap

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Background. Starting from 1993 Estonian newborns were screened for phenylketonuria and three years later congenital hypothyroidism was added to the screening programme. Most developed countries use tandem mass spectrometry in order to screen for a large variety of congenital diseases.

Methods. Early in 2014, 18 new treatable congenital metabolic diseases (aminoacidurias, organic acidurias and fatty acid oxidation disorders with congenital vitamiin B12 deficiency) were included in the Estonian pilot programme on screening newborns by using tandem mass spectrometry.

Results. During 18 months, altogether 20,147 newborns were screened while 43 of them required additional investigations. Confirmed diagnosis was made for 11 patients: one patient had biopterin responsive phenylalanine hydroxylase deficiency, one had low free carnitine, one had glutaric aciduria type I and eight had acquired vitamin B12 deficiency. The positive predictive value was 25.6%. False-positive rate was 0.16%, which diminished after introducing our own cut-off values and applying The Region 4 Stork (R4S) project’s post-analytical interpretative tool.

Conclusions. There are large variations in the design of newborn screening programmes and daily practices in different countries. Hence international cooperation and national cooperation are of great importance, especially in small countries with small screening programmes like Estonia, to improve the competence, efficiency and quality of treatment.