The detection of areas in Poland with an increased prevalence of isolated cleft lip with or without cleft palate

Abstract

Introduction:

It is difficult to identify the environmental factors which together influence the occurrence of congenital malformations. It could be helpful to define the geographic location of the areas with an increased prevalence of such malformations. The aim of this study is to define if there are regions in Poland where the prevalence of isolated cleft lip, with or without a cleft palate (CL±P), is increased, and to present a method for searching for such areas.

Material and Methods:

The analysis included the whole area of Poland monitored in 2007–2008 by the Polish Register of Congenital Malformations (PRCM). The area was divided into 3,045 census regions. The number of children with CL±P in those years was 514, and the size of the reference population (live births) was 802,372. Two methods were used for the detection of clusters with an increased prevalence of isolated CL±P: the LISA analysis and Kulldorff’s scan statistic, and described in detail.

Results:

The prevalence of isolated CL±P and the smoothed prevalence were calculated for every community. The results of the LISA and Kulldorff’s analyses were consistent. Both methods located the sites with an increased prevalence of isolated CL±P. The lack of statistical significance of clusters indicated by Kulldorff’s statistic, and the significance of clusters detected with the use of the LISA method, indicated the existence of clusters with an only slightly increased prevalence of isolated CL±P.

Conclusions:

The study shows the usefulness of the LISA and Kulldorff’s spatial analyses in epidemiological studies, including the etiology of congenital malformations. Because the two methods work in different ways, good results can be obtained when they are used together.