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Biometrics. 1995 Dec;51(4):1570-8.

A mixture model with detection limits for regression analyses of antibody response to vaccine.

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Department of International Health, Johns Hopkins University, School of Hygiene and Public Health, Baltimore, Maryland, USA.


Antibody concentration values as determined by quantitative assays often are left-censored due to detection limits or limits established for purpose of specificity. Standard analyses which assume the data arise from a single lognormal response distribution may not be appropriate, when more observations are censored than would be expected under such a model. Interference from maternal antibodies due to vaccination at an early age, for example, could result in a high proportion of nonresponders to vaccine. A mixture model consisting of a censored lognormal distribution and a point distribution located below the detection limit is proposed for such situations. Antibody data from a study of measles vaccine are used to illustrate the utility of this approach and the interpretation of the model parameters.

[Indexed for MEDLINE]

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