Intracluster correlation coefficients from the 2005 WHO Global Survey on Maternal and Perinatal Health: implications for implementation research

doi:10.1111/j.1365-3016.2007.00901.x

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Wiley InterScience

Paediatric and Perinatal Epidemiology

Volume 22 Issue 2, Pages 117 - 125

Published Online: 20 Feb 2008

Affiliated to the Society for Pediatric and Perinatal Epidemiologic Research

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Methodology

Intracluster correlation coefficients from the 2005 WHO Global Survey on Maternal and Perinatal Health: implications for implementation research

Monica Taljaard ^a , Allan Donner ^b , José Villar ^c , Daniel Wojdyla ^d , Alejandro Velazco ^f , Vicente Bataglia ^g , Anibal Faundes ⁱ , Ana Langer ^j , Alberto Narváez ^k , Eliette Valladares ^l , Guillermo Carroli ^d , Nelly Zavaleta ^m , Archana Shah ⁿ , Liana Campodónico ^d , Mariana Romero ^e , Sofia Reynoso ^o , Karla Simônia de Pádua ⁱ , Daniel Giordano ^d , Marius Kublickas ^p and Arnaldo Acosta ^h for the World Health Organization 2005 Global Survey on Maternal and Perinatal Health Research Group

^a Ottawa Health Research Institute and University of Ottawa, Ottawa, and ^b University of Western Ontario and Robarts Clinical Trials, London, Canada, ^c Nuffield Department of Obstetrics and Gynaecology, University of Oxford, Oxford, UK, ^d Centro Rosarino de Estudios Perinatales (CREP), Rosario, and ^e CONICET/Centro de Estudios de Estado y Sociedad (CEDES), Buenos Aires, Argentina, ^f Hospital Docente Ginecobstétrico 'América Arias', La Habana, Cuba, ^g Department of Obstetrics and Gynaecology, Hospital Nacional de Itauguá, and ^h Department of Obstetrics and Gynaecology, Universidad Nacional de Asunción, Asunción, Paraguay, ⁱ Centro de Pesquisas em Saúde Reprodutiva de Campinas (Cemicamp), Campinas, SP, Brazil, ^j EngenderHealth, New York, NY, USA, ^k Fundación Salud, Ambiente y Desarrollo, Quito, Ecuador, ^l Universidad Nacional Autónoma de Nicaragua, León, Nicaragua, ^m Instituto de Investigación Nutricional, Lima, Peru, ⁿ Department of Reproductive Health and Research (RHR), World Health Organization, Geneva, Switzerland, ^o The Population Council, Latin America Office, Mexico City, Mexico, and ^p Karolinska Institute, Stockholm, Sweden

Correspondence to Dr. Monica Taljaard, Ottawa Health Research Institute and University of Ottawa, Clinical Epidemiology Program, Ottawa Hospital, Civic Campus, 1053 Carling Avenue, F-Wing, F650b, Ottawa, ON K1Y 4E9, Canada.
E-mail: mtaljaard@ohri.ca

KEYWORDS

obstetric care • perinatal care • process variables • intracluster correlation coefficient

Taljaard M, Donner A, Villar J, Wojdyla D, Velazco A, Bataglia V, et al. Intracluster correlation coefficients from the 2005 WHO Global Survey on Maternal and Perinatal Health: implications for implementation research. Paediatric and Perinatal Epidemiology 2008; 22: 117–125.

ABSTRACT

Cluster-based studies involving aggregate units such as hospitals or medical practices are increasingly being used in healthcare evaluation. An important characteristic of such studies is the presence of intracluster correlation, typically quantified by the intracluster correlation coefficient (ICC). Sample size calculations for cluster-based studies need to account for the ICC, or risk underestimating the sample size required to yield the desired levels of power and significance. In this article, we present values for ICCs that were obtained from data on 97 095 pregnancies and 98 072 births taking place in a representative sample of 120 hospitals in eight Latin American countries. We present ICCs for 86 variables measured on mothers and newborns from pregnancy to the time of hospital discharge, including 'process variables' representing actual medical care received for each mother and newborn. Process variables are of primary interest in the field of implementation research.

We found that overall, ICCs ranged from a minimum of 0.0003 to a maximum of 0.563 (median 0.067). For maternal and newborn outcome variables, the median ICCs were 0.011 (interquartile range 0.007–0.037) and 0.054 (interquartile range 0.013–0.075) respectively; however, for process variables, the median was 0.161 (interquartile range 0.072–0.328). Thus, we confirm previous findings that process variables tend to have higher ICCs than outcome variables. We demonstrate that ICCs generally tend to increase with higher prevalences (close to 0.5). These results can help researcherscalculate the required sample size for future research studies in maternal and perinatal health.

DIGITAL OBJECT IDENTIFIER (DOI)

10.1111/j.1365-3016.2007.00901.x About DOI