摘要:Phenylketonuria is a disease caused by congenital defects in phenylalanine metabolism and leads to irreversible damage to the nerve cells. However, detection in early days of life can reduce the severity of the disease. Thus, many countries have started disease screening programs for neonates. The present study aimed to determine the worldwide prevalence of classic phenylketonuria using the data of neonatal screening studies. PubMed, Web of Sciences, Sciences Direct, ProQuest, Scopus databases were searched for related articles. The quality of the articles was evaluated using the Joanna Briggs Institute Critical Appraisal Evaluation Checklist. A random effect was used to calculate the pooled prevalence, and PKU prevalence per 100 000 neonates was reported. A total of 53 studies with 119 152 905 participants, conducted during 1964-2017, were included in this systematic review. The highest prevalence (38.13) was reported in Turkey and the lowest (0.3) in Thailand. A total of 46 studies were entered into the meta-analysis for pooled prevalence estimation. The overall worldwide prevalence of the disease is 6 per 100 000 neonates (95% CI, 6.07-5.07). The results of the meta-regression test showed that heterogeneity in the worldwide prevalence of the disease is high (I2 = 99%). Heterogeneity in the worldwide prevalence of phenylketonuria is high, which can be due to differences in factors affecting the disease, such as consanguineous marriages and genetic stores in different countries, differences in the study performance and diagnostic tests, cutoff points, and sample size.