Prevalence of Phenylketonuria in neonates of Mashhad, Iran: A cross-sectional study
Authors: Rouzbahani Arian Karimi , Pajouhi Ali , Dadkhah Mohammad , Behzadifar MohammadMahdi , Farhat Ahmad Shah , Mohammadzade Ashraf , Khodashenas Ezzat , Ma'amoori GholamAli , Baskabadi Hasan , Faramarzi Rahele , Baskabadi Abbas , Taghipour Ali , MosaFarkhani Ehsan , Hoseini Seyed Javad 
Published: May 2023

Abstract
Introduction: Phenylketonuria (PKU) is a rare genetic disorder, caused by impaired phenylalanine hydroxylase (PAH) gene activity, resulting in high levels of phenylalanine in the body fluids. Such condition increases the risk of cognitive issues and requires limited diet plans with medications such as Sapropterin dihydrochloride for treatment. PKU affects approximately 6.002 individuals per 100,000 neonates worldwide; however, variations exist among populations depending on genetics and other factors that determine their vulnerability to this condition. This research aims to investigate incidence rates among Mashhad neonates for a better understanding of its prevalence. The provision of effective screening and treatment interventions can confer significant benefits on those requiring medical attention, helping healthcare professionals and decision-makers identify essential areas for resource allocation in the face of addressing health concerns.
Method: A cross-sectional survey based on demographics was conducted in the geographical area of Mashhad, Iran during the years 2018-2020. Out of 315,414 neonates in this study (161,626 male and 153,788 female), 83 neonates (0.026290%) were diagnosed with Phenylketonuria. The age at the time of diagnosis was in the ranges of 3-6, 6-22, and 22≤ days. PKU range (Normal TSH range 0-4.9 mIU/L) was taken. According to the instructions for performing the screening test, from the beginning of April 2018 to the beginning of April 2020, 5 drops of blood were taken from the heel of the foot with a lancet and spread on a special filter paper approved by the Ministry of Health called S903&S. Immunoenzymatic ELISA method has been used to measure phenylalanine. SPSS version 25 software was used to analyze the data.
Result: Out of 83 neonates diagnosed with PKU, 99.9% (315324), 0.02% (77), 0.004% (13) and 0.0% (0) neonates had under 4, 4-9.9, 10-19.9 and over 20 mg/dL phenylalanine in the blood. 40.9% of neonates were born with non-familial parents, but 4.8%, 6.02, 45.8%, and 2.4% were born to grade 1, grade 2, grade 3, and grade 4 and more, respectively. 75(90.4%), 4(4.8%), and 1(1.2%) neonate used breast milk, Infant formula, and hybrid, respectively. The type of delivery was natural birth and C-section for 58(69.9%) and 25(30.1%) neonates, respectively. 73(88.0%) of neonates were born after the 37th week of pregnancy, and 10(12.0%) were born prematurely. None of the neonates were multiple birth.
Discussion: Prevalence varies around the world, with an average of about 1 in 10,000 babies being born. Early diagnosis is based on neonatal screening, and if treatment is started early and continued, intelligence is in the normal or average range, some neurological functions are less than desirable. The annual cost of caring for a phenylketonuria patient was much higher than the cost of caring for a screening individual. Fortunately, 96.3% (303754 people) of the infants of our statistical population referred for screening tests between 3 and 7 days after birth. And 3.7% (11,660) of infants were referred after 8th birthday.
Conclusion: According to this study, the frequency of PKU in the targeted population is approximately 1 in 3800, which is much higher than the global average. This makes the neonates screening program a necessary and important step, and the diagnoses should occur as soon as possible to reduce the disease's comorbidities.