Epidemiology and Infection

Original Papers

Analysis of rubella antibody distribution from newborn dried blood spots using finite mixture models

P. HARDELIDa1 c1, D. WILLIAMSa1, C. DEZATEUXa1, P. A. TOOKEYa1, C. S. PECKHAMa1, W. D. CUBITTa2 and M. CORTINA-BORJAa1

a1 MRC Centre of Epidemiology for Child Health, UCL Institute of Child Health, London, UK

a2 Department of Virology, Great Ormond Street Hospital NHS Trust, London, UK

SUMMARY

Eluted dried blood spot specimens from newborn screening, collected in 2004 in North Thames and anonymously linked to birth registration data, were tested for maternally acquired rubella IgG antibody as a proxy for maternal antibody concentration using an enzyme-linked immunosorbent assay. Finite mixture regression models were fitted to the antibody concentrations from 1964 specimens. The Bayesian Information Criterion (BIC) was used as a model selection criterion to avoid over-fitting the number of mixture model components. This allowed investigation of the independent effect of maternal age and maternal country of birth on rubella antibody concentration without dichotomizing the outcome variable using cut-off values set a priori. Mixture models are a highly useful method of analysis in seroprevalence studies of vaccine-preventable infections in which preset cut-off values may overestimate the size of the seronegative population.

(Accepted January 14 2008)

(Online publication February 25 2008)

Correspondence:

c1 Author for correspondence: Ms P. Hardelid, MRC Centre of Epidemiology for Child Health, UCL Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK. (Email: p.hardelid@ich.ucl.ac.uk)

Metrics