Analytical performance of the fluorometric method in the early diagnosis of phenylketonuria: the experience of the imc neonatal screening laboratory over the 2015–2025

Abstract

Summary. Introduction. Phenylketonuria (PKU) is an autosomal recessive metabolic disorder caused by a deficiency in the phenylalanine hydroxylase enzyme. Without early detection and immediate dietary management, the toxic accumulation of phenylalanine leads to severe, irreversible intellectual disability. Material and methods: This study presents a retrospective evaluation of the national PKU screening program in the Republic of Moldova, focusing on the 11-year continuous period from 2015 to 2025. Results: Out of 341,195 recorded births, a total of 326,064 newborns underwent primary screening, yielding a robust and sustained average national coverage rate of 95.56%. A detailed diagnostic analysis of the final consecutive periods, 2024 and 2025, demonstrated an ideal clinical sensitivity of 100% with zero false-negative cases. Clinical specificity improved from 0.988 in 2024 to 0.995 in 2025, while the absolute volume of false-positive alarms dropped significantly from 264 to 91 cases. Consequently, the Positive Predictive Value (PPV) experienced a significant, nearly twofold expansion, rising from 0.011 to 0.021. This clinical shift demonstrates that the probability of an initial positive screening result representing a genuine, confirmed case of PKU nearly doubled between the two focal cycles, thereby optimization clinical recall pathways and minimizing unnecessary parental anxiety. Conclusion: The results confirm the high logistical efficiency and clinical safety of the current infrastructure. To optimize the screening loop further and reduce the recall burden, transitioning the centralized reference laboratory toward multiplex analytical platforms, such as Tandem Mass Spectrometry (MS/MS) and Nuclear Magnetic Resonance (NMR) spectroscopy, is highly recommended.