Reporting of perinatal health indicators for international comparisons-enhancing the appearance of geographical plots

Abstract

Background: Tabulating annual national health indicators sorted by outcome may be misleading for two reasons. The implied rank order is largely a result of heterogeneous population sizes. Distinctions between geographically adjacent regions are not visible. Methods: Regional data are plotted in a geographical map shaded in terms of percentiles of the indicator value. Degree of departure is determined relative to control limits of a corresponding funnel plot. Five methods for displaying outcome and degree of departure from a reference level are proposed for four indicators selected from the 2004 European Perinatal Health Report. Results: Spread of indicator values was generally largest for small population sizes, with results for large populations lying mostly close to respective European medians. The high neonatal mortality rate for Poland (4.9 per 1000); high low-birthweight rates for England and Wales (7.8%), Germany (7.3%) and Estonia (4.5%); and high caesarean section rates for Italy (37.8%), Poland (26.3%), Portugal (33.1%) and Germany (27.3%) were statistically significant exceptions to this pattern. Estonia also showed an extreme result for maternal mortality (29.6 per 100 000). Conclusion: Extreme deviations from EU reference levels are either correlated with small population sizes or may be interpreted in terms of differing medical practices, as in the case of caesarean section rate. EURO-PERISTAT has now decided to use 5-year averages for maternal mortality to reduce the variance in outcome. Use of two colours in three intensities and solid fill versus crosshatching is best suited to display rate and significance of difference. © 2013 The Author.