High Birth Prevalence Rates for Congenital Anomalies in South American Regions

GILI JA; POLETTA FA; PAWLUK MS; GIMENEZ LG; CAMPAÑA H; CASTILLA EE; LOPEZ CAMELO, JS

EPIDEMIOLOGY

LIPPINCOTT WILLIAMS & WILKINS

Lugar: Philadelphia; Año: 2015

1044-3983

The Latin-American Collaborative Study of CongenitalMalformations (ECLAMC) network has studied thefrequencies of congenital anomalies in South America for over 40 years and hasreported heterogeneous rates across countries for some birth defects.Cluster detection using spatial scan analysis4 may be an efficientapproach to identifying environmental and/or genetic factors involved in birthdefects. This statistical method has the advantage of delimiting areas of highbirth prevalence rate independent of political boundaries, which renders thisapproach useful for identifying etiologic factors and generating causalhypotheses regarding the specified geographic areas.We conducted an ecological study to identify regionswith a high birth prevalence rates of specific isolated congenital anomalies inSouth America, using clinical epidemiologic data registered by the ECLAMCnetwork. A total of 25,082 malformed newborns were ascertained from 2,557,424births at 129 hospitals in South America between 1995 and 2012. Each case wascodified as one of 17 congenital anomalies categories. We selected thefollowing categories because they are conspicuous, have a high observationalvalue at birth, or are of high clinical-epidemiologic value for health policy. Theisolated congenital anomalies were: anencephaly, encephalocele (at any level),hydrocephaly, spina bifida (with or without hydrocephalus, at any level),microtia, cleft palate only, cleft lip only, cleft lip with cleft palate, cleftlip with or without cleft palate, esophageal atresia (with or without fistula,at any level), hypospadias (any grade), postaxial polydactyly (feet or hands),preaxial polydactyly (feet or hands), diaphragmatic hernia, omphalocele,gastroschisis, and Down syndrome.We used the Spatial Scan Statistic to determine geographicalregions with high birth prevalence rate of congenital anomalies. We assesseddifferences in ascertainment by including dummy variables for each hospital ina Poisson regression that captures the fixed effects of the mean frequency inthe regression coefficient for each hospital. We calculated the birthprevalence rate and 95% confidence intervals. For the regression model, weadjusted the standard errors according to the Huber method to consider outlyingvalues or correlations among hospitals located in the same region.We identified five high birth prevalence rate regionsassociated with five congenital anomalies in South America . Hospitals from Cañar and Azogues regions in Ecuador have ahigh birth prevalence rate of oral clefts and microtia, which weresystematically reported by the ECLAMC network.Both of these congenitalanomalies have been associated with high altitude, Amerindian ancestry, and lowsocioeconomic status, three factors shared between the regions and these twoanomalies. It is also worth noting that this region is reported to have highlevels of consanguinity, a key factor to be considered indiseases with a strong genetic component.