Past, present and future of newborn screening in Chile

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1 DOI /s RESEARCH REPORT Past, present and future of newborn screening in Chile V. Cornejo & E. Raimann & J. F. Cabello & A. Valiente & C. Becerra & M. Opazo & M. Colombo Received: 25 February 2010 /Revised: 9 June 2010 /Accepted: 29 June 2010 # SSIEM and Springer 2010 Abstract The history of the Newborn Screening Program in Chile begins in 1984, when a pilot plan was developed that demonstrated the feasibility of its implementation. In 1992, the Ministry of Health started a national newborn screening program for phenylketonuria (PKU) and congenital hypothyroidism (CH), and in 1998, this was extended to the entire country. Throughout this period, a total of 2,478,123 newborns (NB) have been analyzed, obtaining initial coverage of 48.8%, which was later increased to 87.7%, and at present it is at 98.7% of all NB of our Communicated by: Rodney Pollitt Competing interest: None declared. V. Cornejo : E. Raimann : J. F. Cabello : A. Valiente Laboratory of Genetics and Metabolic Diseases, Institute of Nutrition and Food Technology (INTA), University of Chile, Santiago, Chile J. F. Cabello : M. Colombo Laboratory of Metabolic Diseases, Hospital Carlos Van Buren, Valparaiso, Chile C. Becerra Program of Child Health and Department of Public Health Policy, Ministry of Health of Chile, Santiago, Chile M. Opazo Clinical Laboratory of Medical Specialties, Regional Clinical Hospital of Concepción, Guillermo Grant Benavente, Concepcion, Chile V. Cornejo (*) Laboratorio de Genética y Enfermedades Metabólicas, Instituto de Nutrición y Tecnología de los Alimentos (INTA), Universidad de Chile( Av. El Líbano 5524, Macul, Santiago, Chile vcornejo@inta.cl country. During this period, 131 cases with PKU have been diagnosed, resulting in an incidence of 1:18,916 NB, an average age of diagnosis of 18±10.2 days and average phenylalanine level of 19,9±8.8 mg/dl. In relation to CH, 783 cases have been confirmed, arriving at an incidence of 1:3,163 NB, with average age of diagnosis of 12.5± 6.9 days. Due to the good results of the program, the government is evaluating the initiation of an extended pilot program, to introduce other pathologies. Introduction In the twenty-first century, technological advances have changed the traditional approach of health care, and we watch with preoccupation as every day this technology increasingly separates the developed countries from those still on the road to development, a situation that is demonstrated in the neonatal diagnosis of Inborn Errors of Metabolism (IEM). This is the case for many Latin American countries, as newborn screening of some IEM is carried out only in 49.3% of newborns (NB) and very few rely on national programs (Borrajo 2007). Chile at this moment is at an advanced stage of demographic epidemiological transition, caused by a decrease in the rate of infantile mortality and of fertility and by the increase in the survival rate, resulting in health challenges that are different from those of the past century. An example is the reduction in the rate of mortality in children under 1 year, which fell from 50.1 per in 1977 to 7.9 in 2008, which means that the mortality risk was reduced by 84.2% in the last 3 decades. This is mainly attributed to the decrease of infections and to the disappearance of primary malnutrition, which means that genetic and metabolic diseases are acquiring relevance in public

2 health, these having been the second cause of infantile mortality ( In addition, it should be pointed out that the improvement of social and cultural conditions, and the quality of life of the population, among other aspects, have influenced in the relevant reduction in birth rate, which is reflected in the decrease of the number of NB; in 1992, there were 293,787 births, and in 2008 this fell to 240,569 ( minsal.cl). It must be indicated that 75% of them were taken care of by the public system and the remaining 25% by private services. Considering this new epidemiologic scenery, in 1992, the Ministry of Health initiated a Newborn screening program for the diagnosis of phenylketonuria (PKU) (Mc Kusick ) and primary congenital hypothyroidism (CH) (Mc Kusick ). History of the Newborn Screening Program In 1984, through an agreement between the Ministry of Health and the Institute of Nutrition and Food Technology (INTA), University of Chile, a pilot program began to be carried out for the PKU neonatal screening in the central area of Santiago, with the aim of analyzing births and finding out the feasibility of implementing this type of program in Chile. This project lasted 1 year, analyzing 10,000 NB and obtaining 90% coverage. It was concluded that it was feasible to develop programs for neonatal screening, due to the organization of the health system in our country and to the fact that 99.7% of births occurred in a hospital environment. During this period, no NB with PKU were diagnosed and the government did not consider this program as a priority (Cornejo and Colombo 1986). In 1988, a study was published which established that the age of diagnosis for PKU was made at an average age of 3 years 11 months, when mental retardation already existed (Colombo et al. 1988). Considering the urgency to begin the early diagnosis of PKU, in 1989 INTA, together with the Health Service of West Santiago in its rural area, initiated a screening program for PKU and CH, covering 20% of the population of NB in the country. The results were categorical, establishing a PKU incidence of 1:14,640 NB and of 1:2,000 NB for CH, findings which allowed the establishment of a favorable cost benefit relationship, validating its implementation as a national program (Cornejo et al. 1990). In 1992, the Ministry of Health of Chile decided to begin the newborn screening program for PKU and CH, implementing it in the 13 regions into which our country is geographically divided. But it was just recently, in 1998, that the program managed to cover the entire country (Cornejo et al. 2003). The strategy to obtain good coverage was to train the professionals of each hospital in the whole country, teaching them the correct technique of obtaining the sample of dried blood spot (DBS) and the shipment of cards to the regional laboratories. Along with this, they were instructed on the meaning of the neonatal screening programs, the impact that they generate in the population, the organization of the program, and the responsibilities of each of the involved professionals (Cornejo et al. 2007). Organization The national newborn screening program of PKU and CH was planned according to the experience obtained in developed countries (Wilcken and Webster 1991; American Academy of Pediatrics, Committee on Genetics 1992; Therrell and Hannon 2006; Therrell and Adams 2007). The first level is made up of a technical adviser committee with management knowledge and capacity to carry out the program with efficiency and effectiveness. It is constituted by the head of the infantile programs of the Ministry of Health, academics from the Laboratory of Genetics and Metabolic Diseases of the Institute of Nutrition and Food Technology (INTA), Universidad de Chile, the heads of Central and Southern regional laboratories for PKU-CH, and a member of the Scientific Societies of Child Neurology, Pediatrics and Endocrinology. In order to give sustaintability and continuity, responsibilities and specific activities were assigned (Table 1). The second level is comprised of two regional laboratories for neonatal screening. One of them is situated in the center of the country and analyzes 76% of NB and the other is in the south of Chile and analyzes the remaining 24%. Table 1 Responsibilities of the advisory committee of the program of neonatal screening in Chile Committee responsibilities To plan, develop, and evaluate the program of neonatal screening To evaluate and introduce other feasible diseases to diagnose and treat To support the health teams in charge of the follow-up of positive cases To establish policies, protocols and procedures for the programs of neonatal screening and treatment To evaluate the program at least once a year To publish obtained results of the development and evolution of the program of neonatal screening

3 The professionals in charge of taking the DBS are included, establishing their responsibilities (Table 2), and the requirements that the NBs have to fulfill for being evaluated (Table 3). The third level includes reference centers to carry out follow-up of cases diagnosed with these pathologies. This level allows fulfilment of the primary target of the newborn screening program, which is to prevent mental retardation. In order to unify criteria, protocols of treatment and longterm follow up for each pathology were created (Cornejo et al. 2007). The technique of blood collection is by heel puncture on a filter paper card (Scheicher and Schuell 903). For the neonatal screening of PKU, fluorometry method is used and the normal cut-off point established is of 2.0 mg/dl (120 μmol/l) of phenylalanine (Phe). The diagnosis is confirmed by tandem mass spectrometry (MS/MS). The classical PKU is diagnosed when the Phe values are over 20 mg/dl (>1,200 μmol/l). For CH, the value of TSH is measured by Delfia, the normal cut-off point is over 20 mu/ml in DBS. The diagnosis is confirmed measuring thyroid-stimulating hormone (TSH), thyroxine (T 4 ), triiodothyronine (T 3 ) and free thyroxine (T 4L ) in serum and thyroid scintigraphy with Tc99. The CH is confirmed when the TSH is over 10 mu/ ml and T 4 less than 10 ug/dl in serum (Cornejo et al. 2007). Financial support The program counts on tax contributions, resources that can only be used in the implementation and development of the two regional laboratories for PKU and CH. Legislation In July 2005, law Nº 19,966 of the program of explicit guarantees in health, in the general regime of health guarantees, was approved, where the obligatory nature of the neonatal diagnosis for PKU and CH in all NB of the country was established (Ministry of Health 2005; www. supersalud.cl/normativa/571/articles-3174_recurso_1.pdf ). Results From March 1992 to December 2008, a total of 2,478,123 NB have been analyzed, with 0.3% of false positives. At the beginning of the program, a 48.8% coverage was obtained, which was increased in 1998 to 87.7%, when the program was expanded at a national level. At present, 98.7% of NB of the country are bing examined. Our country is more than 4,200 km long, therefore the time that elapses between taking the sample and its reception at the laboratory is of extreme importance. The collection of BDS is as an average of 3.6±0.4 days of life of NB, variations being observed between different health areas of the country. The time elapsed between the taking of the sample in maternity and the reception at the laboratory is on average 7.1±0.2 days. During this period, 131 cases with PKU (incidence of 1:18,916 NB) and 243 children with hyperphenylalaninemia have been diagnosed (incidence of 1:10,198 NB). Only two cases have been false negatives; one due to laboratory error and the other due to early discharge of maternity. In relation to CH, 783 children with classic CH (incidence of 1:3,163 NB) and 213 cases with hyperthyrotrophinemia have been confirmed (incidence of 1:11,634 NB). The average value of TSH in DBS was 218.7±31.8 mu/ml and the diagnosis was confirmed at an average age of 12.5±6.9 days. There were 8 cases of false negatives, 6 cases due to early discharge from maternity, a case of secondary hypothyroidism and the other that occurred had normal values of TSH at 48 h, and later developed CH. Protocols of follow-up For PKU, the initiation of a diet restricted in Phe was established when the level of Phe in plasma was over Table 2 Responsibility of the professional who takes the blood sample in filter paper card Professional's responsibilities To educate the pregnant woman and relatives of newborns To take the sample according to the effective norm (heel puncture preferably) To send collected cards to the respective PKU-CH regional laboratory To take note of any newborn with a suspicious result in the first sample, and/or for study of diagnostic confirmation To take the second confirming sample To send to the corresponding PKU-CH regional laboratory the monthly registry of the DBS taken PKU Phenylketonuria, CH congenital hypothyroidism, DBS dried blood sample

4 Table 3 Requisites that newborn must have at the time of taking a dried blood sample in filter paper Requisites for taking blood sample To have completed more than 40 h of life, or the nearest at time of discharge, as far as possible not superior to 7 days of age To be receiving milk feeding. If it is with parental feeding it must be pointed out Neonates born between 36 and 37 weeks of gestation must be examined on the 7th day of age With less than 35 weeks of gestation they must be examined on the seventh day and a second sample at 15 days of life must be repeated Newborn with any pathology must always be examined whenever they fulfill the previous requirements, not wait for the time of discharge If newborn has received transfusion or plasmapheresis examine after 72 h 6.0 mg/dl (360 μmol/l). The government subsidizes the Phe-free formula. INTA was designated as a reference center for diagnostic confirmation and follow-up of positive cases. Of the total of confirmed cases, the average age of diagnosis was 18±10 days, and Phe values of 19.9±8 mg/ dl (1.194±48 μmol/l). The protocol of follow-up in CH considers supplementation with levothyroxine, familiar history of goiter, hyper or hypothyroidism, x-rays of knees, anthropometrical, neurological, psychological and endocrinological evaluations, and serum determinations of TSH, T 4, T 3, T 4L, periodically (Cuello et al. 2004). Of a total of 273 cases confirmed with CH on whom thyroid scintigraphy was performed, it could be established that 38.8% were ectopias, being the most frequent cause (Table 4). Projections of the extended newborn screening program Since 1990, tandem mass spectrometry (MS/MS) has been integrated into neonatal screening, which permits the diagnosis of more than 30 IEM (American Academy of Pediatrics Newborn Screening Authoring Committee 2008; Centers for Disease Control and Prevention (CDC) 2008). Through the development of expanded neonatal screening programs, it has been possible to determine that the incidence for the IEM varies between 1:3,000 to 1:5,000 NB (Schulze et al. 2003; Frazier et al. 2006; Wilcken 2007; Bodamer et al. 2007; Dietzen et al. 2009). Table 4 Classification of congenital hypothyroidism (CH) according to result of 273 thyroid scintigraphy Classification CH cases (n) % Ectopia Goiter Without contrast Less contrast Normal Gland absence Total Taking into consideration that the national screening program for PKU and CH works in adequate form with excellent coverage, the Chilean Ministry of Health is evaluating the possibility of increasing the number of pathologies to screen by MS/MS. The Chilean experience in the use of MS/MS began in 2002, in the Laboratory of Genetics and Metabolic Diseases at INTA, to establish the diagnosis of an IEM in patients with clinical symptomatology. In 2007, a pilot program for neonatal diagnosis began using this technique. Table 5 Diagnosis of IEM through MS/MS in Chile (August 2002 February 2009) Disease Propionic acidemia 11 MSUD 11 Glutaric acidemia type 1 8 Isovaleric acidemia 5 Methylmalonic acidemia 7 Citrullinemia 4 MCADD 3 SCADD 3 UCD 2 Argininosuccinic acidemia 1 CPT I 1 B-Ketothiolase deficiency 1 OTC deficiency 1 LCAD 1 Tyrosinemia Type 1 1 VLCAD 1 Homocistinuria 1 NKH 1 Total 63 No. of cases MSUD Maple Syrup Urine Disease, MCADD Medium-Chain-Acyl- CoA Dehydrogenase Deficiency, SCADD Short-Chain Acyl-CoA Dehydrogenase Deficiency, UCD Urea Cycle Disorders, CPT I Carnitine Palmitoyltransferase 1 Deficiency, OTC Ornithine Transcarbamylase, LCAD Long-Chain Acyl-CoA dehydrogenase Deficiency, VLCAD Very Long-Chain Acyl-CoA Dehydrogenase Deficiency, NKH Nonketotic Hyperglycinemia

5 Between August 2002 and February 2009, a total of 22,439 DBS have been analyzed, of which 40% have been for neonatal screening and 60% for clinical suspicion of an IEM. Of the total DBS samples of children with clinical symptoms, the diagnosis of an IEM was made in 63 cases, being the most frequent pathologies after PKU, propionic academia (PA) and maple syrup urine disease (MSUD). The diagnosed cases are shown in Table 5, the cases with PKU were not included since this laboratory only confirms cases suspected in the national newborn screening program of PKU and CH. Of the total of samples analyzed for newborn screening, 92 samples were false positive and discarded in a second sample. With these results, a rate of 1.02% of recalls was obtained. Samples were collected on average at 2.8 days of life of the NB and received in the laboratory on average at 4.2 days, both parameters considered adequate according to that described in the literature (Wilcken et al. 2009). This laboratory is affiliated to the Quality Program of Control Disease Center (CDC) To date, all reports have had 100% agreement with the quality controls, which allows the conclusion that the pre-analytical, analytical, and postanalytical analyses are being performed within the necessary parameters for an extended newborn screening program (Centers for Disease Control and Prevention (CDC) 2008). At the moment, the government is analyzing a pilot project to apply an expanded program of neonatal screening, where 9 IEM would be included, including PKU. Conclusions and perspectives The national neonatal screening program in Chile has managed to maintain coverage of near 100% of NB, obtaining in 16 years the diagnosis and prevention of mental retardation in 914 children. Nevertheless, the challenges for the future are very important, since to start an extended newborn screening program implies increasing the number of pathologies of greater biochemical and clinical complexity (Wilcken 2008). According to the incidence obtained for PKU (1: 18,916 NB), in Chile every year 13 children are born with classical or variant PKU. If we extrapolated the incidence of 1:4,300 NB obtained in the program of extended neonatal screening of North Carolina (Frazier et al. 2006), 60 children with some IEM should be born in Chile every year. If we discounted the cases with PKU, 47 children would remain undiagnosed during the neonatal period, which means severe sequelas or death during the first months of life (Cornejo et al. 2002). Considering that genetic and metabolic diseases are the second cause of infantile mortality, and that PA and MSUD are the most frequent IEM after PKU, and that for both there is significant scientific evidence that the diagnosis and early treatment avoids neurological damage, we can conclude that it is imperative to begin an extended program of neonatal screening in our country. Acknowledgements We thank all the personnel who work in the laboratory of neonatal screening for PKU and CH at Hospital San Juan de Dios in Santiago and the Regional Laboratory of PKU-CH at Hospital Guillermo Benavente in Concepción, the professional midwives for their correct collection of blood samples in DBS, and the families of the children with PKU and CH. References American Academy of Pediatrics, Committee on Genetics (1992) Issues in newborn screening. Pediatrics 89: American Academy of Pediatrics Newborn Screening Authoring Committee (2008) Newborn screening expands: recommendations for pediatricians and medical homes implications for the system. Pediatrics 121: Bodamer OA, Hoffmann GF, Lindner M (2007) Expanded newborn screening in Europe J Inherit Metab Dis 30: Borrajo G (2007) Newborn screening in Latin America at the beginning of the 21st century. J Inherit Metab Dis 30: Centers for Disease Control and Prevention (CDC) (2008) Impact of expanded newborn screening United States, Morb Mortal Wkly Rep 57: Colombo M, Troncoso L, Raimann E, Perales CG, Barros T, Cornejo V (1988) Diagnóstico de Fenilquetonuria en Chile. Rev Chil Pediatr 59: Cornejo V, Colombo M (1986) Diagnóstico precoz de fenilquetonuria y prevención de retardo mental. In: Cornejo V, Colombo M (eds) Tesis para optar al grado de Magister en Nutrición Humana INTA. Universidad de Chile, Santiago, Chile, pp 1 67 Cornejo V, Raimann E, Moraga M, Colombo M (1990) Programa de rastreo neonatal de fenilquetonuria. Rev Chil Pediatr 61: Cornejo V, Colombo M, Durán G et al (2002) Diagnosis and follow up of 23 children with organic acidurias. Rev Med Chile 130: Cornejo V, Raimann E, Colombo M (2003) Implementación y desarrollo de los programas de detección neonatal., In Colombo M, Cornejo, E., Raimann, E (eds). Errores innatos en el metabolismo del niño, Universitaria, Cornejo V, et al (2007) Normas para el óptimo desarrollo de programas de búsqueda masiva de Fenilquetonuria (PKU), e Hipotiroidismo Congénito (HC) y otros errores congénitos del metabolismo. Editorial Ministerio de Salud, División de Prevención y Control de Enfermedades, República de Chile. Norma general técnica nº 93, Cuello X, Pérez P, Vivanco X, Lobo G, Bruggendiek B, Pérez A (2004) Evaluación de 7 años de programa nacional de detección precoz de hipotiroidismo congénito en Chile. Bol Hosp San Juan de Dios 51: Dietzen DJ, Rinaldo P, Whitley RJ et al (2009) National academy of clinical biochemistry laboratory medicine practice guidelines: follow-up testing for metabolic disease identified by expanded newborn screening using tandem mass spectrometry; executive summary. Clin Chem 55: Frazier DM, Millington DS, McCandless SE et al (2006) The tandem mass spectrometry newborn screening experience in North Carolina: J Inherit Metab Dis 29:76 85

6 la Marca G, Malvagia S, Pasquini E et al (2008) The inclusion of succinylacetone as marker for tyrosinemia type I in expanded newborn screening programs. Rapid Commun Mass Spectrom 22: de Salud M, de Chile G (2005) Documentos, Ley : régimen general de garantías de salud. Rev Chil Obstet Ginecol 70: Schulze A, Linder M, Kohlmuller D, Olgemoller K, Mayatepek E, Hoffmann G (2003) Expanded newborn screening for inborn errors of metabolism by electrospary ionization-tandem mass spectrometry: results, outcome, and implications. Pediatrics 111: Therrell BL, Adams J (2007) Newborn screening in North America. J Inherit Metab Dis 30: Therrell BL, Hannon WH (2006) National evaluation of US newborn screening system components. Ment Retard Dev Disabil Res Rev 12: Wilcken B (2007) Recent advances in newborn screening. J Inherit Metab Dis 30: Wilcken B, Webster D (1991) Neonatal screening in the nineties. In: Wilcken B (ed) International Neonatal Screening Symposium. Excepta Médica, Sydney Australia, p 372 Wilcken B, Haas M, Joy P et al (2009) Expanded newborn screening: outcome in screened and unscreened patients at age 6 years. Pediatrics 124: Wilcken B (2008) The consequences of extended newborn screening programmes: do we know who needs treatment? J Inherit Metab Dis 31: