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Estimating herd‐specific force of infection by using random‐effects models for clustered binary data and monotone fractional polynomials
Author(s) -
Faes Christel,
Hens Niel,
Aerts Marc,
Shkedy Ziv,
Geys Helena,
Mintiens Koen,
Laevens Hans,
Boelaert Frank
Publication year - 2006
Publication title -
journal of the royal statistical society: series c (applied statistics)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.205
H-Index - 72
eISSN - 1467-9876
pISSN - 0035-9254
DOI - 10.1111/j.1467-9876.2006.00555.x
Subject(s) - herd , covariate , population , statistics , mathematics , random effects model , contrast (vision) , flexibility (engineering) , herd behavior , econometrics , binary data , binary number , herding , medicine , computer science , veterinary medicine , artificial intelligence , geography , pathology , meta analysis , environmental health , arithmetic , forestry
Summary. In veterinary epidemiology, we are often confronted with hierarchical or clustered data. Typically animals are grouped within herds, and consequently we cannot ignore the possibility of animals within herds being more alike than between herds. Based on a serological survey of bovine herpes virus type 1 in cattle, we describe a method for the estimation of herd‐specific rates at which susceptible animals acquire the infection at different ages. In contrast with the population‐averaged force of infection, this method allows us to model the herd‐specific force of infection, allowing investigation of the variability between herds. A random‐effects approach is used to account for the correlation in the data, allowing us to study both population‐averaged and herd‐specific force of infection. In contrast, generalized estimating equations can be used when interest is only in the population‐averaged force of infection. Further, a flexible predictor model is needed to describe the dependence of covariates appropriately. Fractional polynomials as proposed by Royston and Altman offer such flexibility. However, the flexibility of this model should be restricted, since only positive forces of infection have a meaningful interpretation.