Neonatal screening for cystic fibrosis in São Paulo State, Brazil: a pilot study

• Main Author: Rodrigues,R.
• Publication Date: 2009
• Other Authors: Magalhaes,P.K.R., Fernandes,M.I.M., Gabetta,C.S., Ribeiro,A.F., Pedro,K.P., Valdetaro,F., Santos,J.L.F., Souza,R.M. de, Pazin Filho,A., Maciel,L.M.Z.
• Format: Article
• Language: eng
• Source: Brazilian Journal of Medical and Biological Research
• Download full: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X2009001000017
• topic: Cystic fibrosis; Neonatal screening; Immunoreactive trypsinogen test; Brazil

Cystic fibrosis is one of the most common autosomal recessive hereditary diseases in the Caucasian population, with an incidence of 1:2000 to 1:3500 liveborns. More than 1000 mutations have been described with the most common being F508del. It has a prevalence of 23-55% within the Brazilian population. The lack of population-based studies evaluating the incidence of cystic fibrosis in São Paulo State, Brazil, and an analysis concerning the costs of implantation of a screening program motivated the present study. A total of 60,000 dried blood samples from Guthrie cards obtained from April 2005 to January 2006 for neonatal screening at 4 reference centers in São Paulo State were analyzed. The immunoreactive trypsinogen (IRT)/IRT protocol was used with the cut-off value being 70 ng/mL. A total of 532 children (0.9%) showed IRT >70 ng/mL and a 2nd sample was collected from 418 (80.3%) of these patients. Four affected children were detected at two centers, corresponding to an incidence of 1:8403. The average age at diagnosis was 69 days, and 3 of the children already showed severe symptoms of the disease. The rate of false-positive results was 95.2% and the positive predictive value for the test was 8%. The cost of detecting an affected subject was approximately US$8,000.00 when this cystic fibrosis program was added to an existing neonatal screening program. The present study clearly shows the difficulties involved in cystic fibrosis screening using the IRT/IRT protocol, particularly in a population with no long-term tradition of neonatal screening.