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Open Access Highly Accessed Research article

Estimating adjusted prevalence ratio in clustered cross-sectional epidemiological data

Carlos Antônio ST Santos1, Rosemeire L Fiaccone2, Nelson F Oliveira1, Sérgio Cunha3, Maurício L Barreto3, Maria Beatriz B do Carmo3, Ana-Lucia Moncayo35, Laura C Rodrigues4, Philip J Cooper5 and Leila D Amorim2*

Author Affiliations

1 State University of Feira de Santana, Feira de Santana, Brazil

2 Department of Statistics, Federal University of Bahia, Salvador, Brazil

3 Instituto de Saúde Coletiva, Federal University of Bahia, Salvador, Brazil

4 London School of Hygiene and Tropical Medicine, London, UK

5 Instituto de Microbiologia, Universid San Francisco de Quito, Quito, Ecuador

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BMC Medical Research Methodology 2008, 8:80  doi:10.1186/1471-2288-8-80

Published: 16 December 2008

Abstract

Background

Many epidemiologic studies report the odds ratio as a measure of association for cross-sectional studies with common outcomes. In such cases, the prevalence ratios may not be inferred from the estimated odds ratios. This paper overviews the most commonly used procedures to obtain adjusted prevalence ratios and extends the discussion to the analysis of clustered cross-sectional studies.

Methods

Prevalence ratios(PR) were estimated using logistic models with random effects. Their 95% confidence intervals were obtained using delta method and clustered bootstrap. The performance of these approaches was evaluated through simulation studies. Using data from two studies with health-related outcomes in children, we discuss the interpretation of the measures of association and their implications.

Results

The results from data analysis highlighted major differences between estimated OR and PR. Results from simulation studies indicate an improved performance of delta method compared to bootstrap when there are small number of clusters.

Conclusion

We recommend the use of logistic model with random effects for analysis of clustered data. The choice of method to estimate confidence intervals for PR (delta or bootstrap method) should be based on study design.