Newborn screening for lysosomal disorders in Brazil: A pilot study using customized fluorimetric assays.

Lysosomal storage disorders (LSDs) are a group of genetic disorders characterized by deficiency of specific lysosomal enzymes. In general, patients are clinically normal at birth, and progressively develop severe signs and symptoms. Diagnosis is usually made several years after onset of manifestations, preventing patients to have the benefits of the early treatment. Newborn screening programs are being considered for LSDs to allow early diagnosis and treatment. The present study evaluated the feasibility of a customized screening approach based on modified fluorometric assays with reduced amounts of reagents, substrates and samples for: mucopolysaccharidosis (MPS) type I (MPS I), MPS VI, Fabry, Gaucher, and Pompe diseases. We also evaluated the advantages of including blood chitotriosidase and urinary glycosaminoglycans in the protocol. By the measurement of the specific disease-associated enzymes (plus blood chitotriosidase and urinary glycosaminoglycans) we analyzed 834 de-identified DBS of unselected newborns. No positive case was detected, and the false-positive rates were low. Taking into consideration the limitations of this methodology, we believe that, after defining proper cutoffs, it could be a viable alternative to provide NBS for LSDs by laboratories that may not be able to afford the commercial methods available.

Monitoring of Phenylalanine Levels in Patients with Phenylketonuria Using Dried Blood Spots: a Comparison of Two Methods

Abstract Phenylketonuria (PKU) is caused by deficient activity of phenylalanine hydroxylase (PAH), responsible for the conversion of phenylalanine (Phe) to tyrosine (Tyr). Monitoring of patients with PKU requires the measurement of Phe in plasma using high-performance liquid chromatography (HPLC) or in dried blood spots (DBS) using different techniques to adjust treatment strategy. The objective of this study was to evaluate Phe levels in DBS measured by two different methods and compare them with Phe levels measured in plasma by HPLC. We analyzed 89 blood samples from 47 PKU patients by two different methods: fluorometric method developed in-house (method A) and the commercially available PerkinElmer® Neonatal Phenylalanine Kit (method B) and in plasma by HPLC. The mean Phe levels by method A, method B, and HPLC were 430.4±39.9μmol/L, 439.3±35.4μmol/L, and 442.2±41.6μmol/L, respectively. The correlation values between HPLC and methods A and B were 0.990 and 0.974, respectively (p < 0.001 for both). Our data suggest that methods A and B are useful alternatives for monitoring Phe levels in patients with PKU, with method A being in closer agreement with the reference standard (HPLC).

Medical Costs Related to Enzyme Replacement Therapy for Mucopolysaccharidosis Types I, II, and VI in Brazil: A Multicenter Study.

BACKGROUND: Mucopolysaccharidosis (MPS) type I (MPS I), MPS type II (MPS II), and MPS type VI (MPS VI) are lysosomal storage disorders for which enzyme replacement therapy (ERT) is available. OBJECTIVE: The objective of this study was to evaluate the frequency of medical interventions in a cohort of patients with MPS I, II, and VI on ERT to estimate the impact of direct medical costs associated with the treatment of MPS and compare its frequency with that observed among patients not on ERT. METHODS: This was a multicenter study using a retrospective design including a convenience sampling of Brazilian patients with MPS I, II, and VI. Data on the number and type of medical appointments, hospital admissions, medications used, and surgical procedures performed per patient were obtained through a review of medical records, as were data on ERT. These variables were then compared between patients undergoing ERT and those not on ERT. RESULTS: Thirty-four patients (27 on ERT) were included in the study. Overall, between-group differences were found in median absolute frequencies of hospital admissions and surgical procedures per year, both of which were higher in the non-ERT group. Furthermore, we observed a high rate of failure to record medication dosage regimens. CONCLUSIONS: Our findings suggest that Brazilian patients with MPS I, II, and VI who are on ERT undergo fewer medical interventions, which can lead to a reduction in direct medical costs to the publicly funded health care system. The cost of ERT, however, is extremely high and probably outweighs this reduction.

A terapia de reposição enzimática pode mudar a frequência de intervenções médicas na mucopolissacaridose tipo I? Um estudo retrospectivo e exploratório / Can enzyme replacement therapy change the frequency of medical interventions in mucopolysaccharidosis type I? An exploratory retrospective study

Introdução: A mucopolissacaridose tipo I (MPS I) é uma doença lisossômica (DL) para a qual está disponível a terapia de reposição enzimática (TRE) com laronidase. Objetivo: caracterizar o efeito da TRE em pacientes com MPS I avaliados por um único centro de referências para DL a partir da análise da frequência de intervenções médicas. Métodos: Estudo retrospectivo e exploratório com comparações pré e pós-intervenção. O número/ano/paciente de consultas, medicamentos usados, internações, cirurgias e exames realizados, foi obtido por meio de revisão de prontuário médico. Essas variáveis foram, então, comparadas entre dois períodos: pré-TRE e pós-TRE. Resultados: Nove pacientes (graves=3, atenuados=6) foram incluídos no estudo. A mediana de idade de início da TRE foi 9 anos e a mediana de duração da TRE foi 4 anos. Em média, os pacientes realizaram 90% das infusões previstas para o período. Somente o número de cirurgias/ano/paciente foi dependente do tempo de doença (p=0,0004) e da gravidade do fenótipo (p=0,014). Com relação às comparações pré e pós-TRE, as variáveis que apresentaram diferença significativa (média do número/ano/paciente) foram: exames (pré-TRE=10,2±2,7; pós-TRE=22,5±2,1; p=0,005) e internações (pré-TRE=0,05±0,04; pós-TRE=0,30±0,11; p=0,013). Conclusão: Nossos dados sugerem que a TRE não alterou a história natural da MPS I em relação aos desfechos analisados. Este achado pode ser devido à idade relativamente avançada de início do tratamento no nosso centro.

Background: Mucopolysaccharidosis type I (MPSI) is a lysosomal disorder (LSD) which can be treated with enzyme replacement therapy (ERT) with laronidase. Aim: To describe the effect of ERT on MPSI patients evaluated at a single referral center for LSD by assessing the frequency of medical interventions. Methods: An exploratory, retrospective study with pre- and post-intervention assessments. We reviewed medical records to collect data on the number of medical appointments/year/patient, medications used, hospital admissions, surgeries, and exams performed. These variables were then compared between the pre- and the post-ERT periods.Results: Nine patients (severe=3; attenuated=6) were included in the study.The median age for the start of ERT was 9 years, and the median time on ERT was 4 years. On average, patients received 90% of the infusions predicted for the study period. Only the number of surgeries/year/patient was found to be dependent on length of disease (p=0.0004) and on severity of phenotype (p=0.014). Regarding pre- and post-ERT comparisons, there was a significant difference (mean number/year/patient in exams (pre-ERT, 10.2±2.7; post-ERT, 22.5±2.1; p=0.005) and hospital admissions (pre-ERT, 0.05±0.04; post-ERT, 0.30±0.11; p=0.013). Conclusion: Our data suggest ERT didn’t alter the natural history of MPSI the outcomes assessed in this study. This may be due to the relatively advanced age of patients when they started treatment at our Center.