Estimating the Probability of IQ Impairment from Blood Phenylalanine for Phenylketonuria Patients: A Meta-Analysis

• Activity Number: 184
• Type: Contributed
• Date/Time: Monday, July 30, 2012 : 10:30 AM to 12:20 PM
• Sponsor: Section on Statistics in Epidemiology
• Author(s): Christopher Fonnesbeck*+ and Melissa L McPheeters and Shanthi Krishnaswami and Mary Louise Lindegren and Tyler Reimschisel
• Companies: Vanderbilt University and Institute for Medicine and Public Health and Institute for Medicine and Public Health and Vanderbilt University Medical Center and Vanderbilt University Medical Center
• Keywords: PKU ; Bayesian methods ; meta-analysis ; metabolic disease ; IQ ; hierarchical model

Abstract

PKU is a metabolic disorder in which an inability to properly metabolize protein results in a neurotoxic buildup of Phe in the blood, leading to intellectual disability. The standard treatment of PKU is a diet that restricts intake of Phe to maintain a safe blood concentration. However, there is little empirical basis for the selection of specific Phe levels as targets for dietary control. Because PKU is rare, there are limited data on the most appropriate treatment regimen. We sought to evaluate the evidence that any specific Phe levels are optimal for avoiding impairment in PKU individuals. This work uses a hierarchical meta-analysis of blood Phe-IQ correlation to predict the probability of low IQ for a range of Phe levels. The mean baseline association of Phe with IQ was estimated to be negative, for both historical and concurrent measurement of Phe relative to IQ. Probabilities corresponding to historical measures of Phe demonstrated an increasing chance of low IQ with increasing Phe, with the strongest association seen for Phe measured during the critical period. In contrast, concurrent Phe was more weakly correlated with low IQ.