[Family screening for HBB*S gene and detection of new cases of sickle cell trait in Northeastern Brazil]. / Triagem familiar para o gene HBB*S e detecção de novos casos de traço falciforme em Pernambuco.

ABSTRACT

OBJECTIVE: To estimate the additional number of affected individuals based on the prevalence of sickle-cell syndromes among relatives of index cases. METHODS: Cross-sectional study of relatives of a random sample of index cases identified through a neonatal screening program in Northeastern Brazil, between 2001 and 2005. The extended family trial model included 463 relatives of 21 index cases. Relatives were classified as nuclear family (NF father, mother, and siblings); first degree extended family (N1 grandparents, uncles and aunts, and first cousins); second degree extended family (N2 children of first cousins); extended family (NA NF+N1+N2); and extended nuclear family (NA1 NF+N1). The presence of HBB*S and other abnormal hemoglobins was confirmed by high-performance liquid chromatography. The association between the presence of HBB*S and other variables was calculated using prevalence ratios and their respective 95% confidence intervals, and differences between means were calculated using Student's t test with a 5% significance level. RESULTS: Of relatives, 81% had no knowledge of sickle-cell anemia and HBB*S was present in 114 family members. A total of 53.3% of the studied population was considered as of reproductive age, and 80% of HBB*S carriers had already had children. Frequency was higher among NF (69%), but was also high in N1 (22.8%). NA1 screening resulted in the detection of 69 carriers additional (a 172% increase). CONCLUSIONS: These results indicate that family screening for the identification of sickle-cell carriers should be extended to first degree relatives.