IgG N-glycans as potential biomarkers for determining galactose tolerance in Classical Galactosaemia.

N-glycan processing and assembly defects have been demonstrated in untreated and partially treated patients with Classical Galactosaemia. These defects may contribute to the ongoing pathophysiology of this disease. The aim of this study was to develop an informative method of studying differential galactose tolerance levels and diet control in individuals with Galactosaemia, compared to the standard biochemical markers. Ten Galactosaemia adults with normal intellectual outcomes were analyzed in the study. Five subjects followed galactose liberalization, increments of 300 mg to 4000 mg/day over 16 weeks, and were compared to five adult Galactosaemia controls on a galactose restricted diet. All study subjects underwent clinical and biochemical monitoring of red blood cell galactose-1-phosphate (RBC Gal-1-P) and urinary galactitol levels. Serum N-glycans were isolated and analyzed by normal phase high-performance liquid chromatography (NP-HPLC) with galactosylation of IgG used as a specific biomarker of galactose tolerance. IgG N-glycan profiles showed consistent individual alterations in response to diet liberalization. The individual profiles were improved for all, but one study subject, at a galactose intake of 1000 mg/day, with decreases in agalactosylated (G0) and increases in digalactosylated (G2) N-glycans. We conclude that IgG N-glycan profiling is an improved method of monitoring variable galactosylation and determining individual galactose tolerance in Galactosaemia compared to the standard methods.

[Newborn screening for galactosemia: a health economics evaluation]. / Avaliação econômica em saúde: triagem neonatal da galactosemia.

This study assesses the efficiency of the galactosemia add-on test in neonatal screening performed on regular Guthrie card blood spots. Based on estimated average incidence of galactosemia (1:19,984 newborns) in São Paulo State, Brazil, the study develops a cost-benefit analysis model, using a B/C ratio and a 9.25% annual interest rate in order to decapitalize the results. Sensitivity analysis is also performed, varying (as a function of the interest or discount rate) from 0 and 20% and according to the 95% confidence interval (1:7,494-1:59,953 newborns). The results show that the savings obtained by improved health of galactosemic patients detected early by add-on neonatal screening is superior to the costs (B/C=1.33), characterizing galactosemia add-on testing in neonatal screening as an efficient policy. The lower the prevailing interest rate in the economy, the more efficient the neonatal screening policy.

Galactosaemia in a Brazilian population: high incidence and cost-benefit analysis.

OBJECTIVES: To study the incidence of galactosaemia in the state of São Paulo and the benefit/cost (B/C) ratio of the introduction of neonatal screening for galactosaemia, comparing it with a selective approach. METHODS: An enzymatic-colorimetric assay was used for the screening of total galactose (TG) in a sample of 10% of the births in São Paulo in one year and positive cases were confirmed by the activity of galactose-1-phosphate uridyltransferase (GALT). Detected and referred cases were genotyped using enzyme restriction studies for Q188R, N314D and S135L mutations of the GALT gene. The economic analysis was determined by calculating the B/C ratio and by analysis of sensitivity as a function of the incidence of the disease detected and the variation of the interest rate in the economy. RESULTS: 59 953 newborns were screened for TG, with 3 cases of galactosaemia being identified (0.26% false positives), corresponding to a frequency of 1:19 984 liveborns (95% confidence interval: 1:7494 to 1:59 953). One classical case and one Duarte 2 variant referred to as a selective approach were confirmed. With an incidence of 1:19 984, the B/C ratio was 1.04 for the 11.75% interest rate in effect in Brazil, with values already decapitalized. With a maximum possible incidence of 1:7494, the B/C ratio was 2.79. DISCUSSION: There is an economic advantage in introducing neonatal screening for galactosaemia in the national neonatal screening programme. This advantage could increase with a reduction of the current interest rates in the economy.