Epidemiology of phenylketonuria obtained through neonatal screening

Abstract

INTRODUCTION: Hyperphenylalaninemia, whose most serious form is phenylketonuria (PKU) is an inborn error of phenylalanine (Phe) metabolism. If untreated, results in profound and irreversible mental disability. In Mexico, early detection of this disease was incorporated into the newborn screening program (NBS) of the Ministry of Health in 2011. OBJECTIVE: To present for first time the birth prevalence of hyperphenylalaninemia (HPA) and phenylketonuria (PKU) obtained through newborn screening in Mexico. MATERIAL AND METHODS: From January 1st, 2017 to May 31, 2018, a total of 1,273,727 samples were taken from the heel of newborns (NB) attended by the Ministry of Health of Mexico. Phe was quantified in dry blood by immunofluorometric assay. All the NB with positive screening and whose confirmatory tests showed elevated levels of PHE in blood, low tyrosine (Tyr) and PHE/Tyr ratio >2, where considered as confirmed cases of the disease. The number of HPA/PKU positive screening cases, confirmed cases, false positives as well as the proportion of non-localized cases were analyzed. The statistical analysis was carried out through the free access program Comprehensive R Archive Network. RESULTS: A total of 1,267,122 (99.4%) samples were adequate for Phe quantification from them, 793 were above the cut-off value and were notified as positive screening test. 46 HPA/PKU cases were confirmed. The disease was present in 21 Mexican states. CONCLUSIONS: HPA/PKU birth prevalence rate in México was 3.6 cases per 100.000 newborns, which is equivalent to 1 case in each 27,546 screened NB.